WO2012001870A1

WO2012001870A1 - Solid state imaging device

Info

Publication number: WO2012001870A1
Application number: PCT/JP2011/002789
Authority: WO
Inventors: 洋藤中
Original assignee: パナソニック株式会社
Priority date: 2010-07-01
Filing date: 2011-05-19
Publication date: 2012-01-05

Abstract

Disclosed is a solid state imaging device provided with a function for simultaneously allowing a faster start up, lower noise, and higher dynamic range. The solid state imaging device (1) is provided with: multiple unit pixels (5) arranged in a matrix; a vertical signal line (45) and a read-out current source (50) provided in each pixel row; a voltage conversion circuit (300) for generating a voltage other than the power source voltage; a vertical scanning circuit (40) for driving, with the voltage generated by the voltage conversion circuit (300), the unit pixels (5) in order by row, and reading out the signal voltage for each pixel via the vertical signal lines (45) and the read-out current sources (50); a low bandwidth constant voltage circuit (100) for supplying a first voltage to the read-out current source (50); and a high bandwidth constant voltage circuit (200) for supplying to the voltage conversion circuit (300) a second voltage having a frequency component higher than that of the first voltage.

Description

Solid-state imaging device

The present invention relates to a solid-state image pickup device, and more particularly to a solid-state image pickup device having a function for achieving both high-speed startup, low noise, and high dynamic range.

Solid-state imaging devices that convert light into electrical signals are used in various devices such as digital video cameras, digital still cameras, and facsimiles. As a solid-state imaging device, a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal-Oxide Semiconductor) image sensor are known.

As a conventional CMOS image sensor, a solid-state imaging device having a voltage conversion circuit that generates a voltage different from a power supply voltage and driving a pixel using a voltage generated by the voltage conversion circuit is known. Yes.

Hereinafter, a configuration of a conventional solid-state imaging device described in Patent Document 1 including a booster circuit as a voltage conversion circuit will be described with reference to FIG.

FIG. 14 is a block diagram illustrating a configuration of a conventional solid-state imaging device 1000 disclosed in Patent Document 1. In FIG.

The solid-state imaging device 1000 includes a pixel array 1010 in which a plurality of unit pixels 1003 including a light receiving element that outputs a signal corresponding to the amount of incident light is arranged in a two-dimensional matrix, and a pixel signal is output from each unit pixel 1003. The The unit pixel 1003 is a so-called four-transistor pixel cell, and includes a photodiode 1030, a transfer transistor 1031, a reset transistor 1032, a selection transistor 1033, and a reading transistor 1034. The read transistor 1034 in each unit pixel 1003 forms a source follower circuit (hereinafter referred to as a pixel source follower) by a read current source 1050 provided for each pixel column. Thus, the pixel signal is read out through the vertical signal line 1045 by the pixel source follower circuit.

The solid-state imaging device 1000 further includes a booster circuit 1100, a vertical scanning unit 1040, a horizontal scanning unit 1060, a horizontal selection transistor 1061, an amplifier 1069, an AD conversion unit 1080, and a signal processing unit 1090. The vertical scanning unit 1040 drives the transistors 1031 to 1033 in the selected row, thereby resetting the photodiode 1030 and reading out the pixel signal. The read pixel signals are sequentially supplied to the amplifier 1069 via the horizontal signal line 1062 when the horizontal scanning unit 1060 selects the horizontal selection transistors 1061 in the column order. The pixel signal read to the amplifier 1069 is AD-converted by the AD conversion unit 1080, subjected to signal processing by the signal processing unit 1090, and then output from the solid-state imaging device 1000 to the outside.

The booster circuit 1100 generates a boosted voltage higher than the input power supply voltage by a voltage conversion operation such as a charge pump, and supplies the boosted voltage to the vertical scanning unit 1040. The vertical scanning unit 1040 drives the transfer transistor 1031, the reset transistor 1032, and the selection transistor 1033 through the transfer transistor control line 1041, the reset transistor control line 1042, and the selection transistor control line 1043, respectively, using the boosted voltage. To do.

Here, when the vertical scanning unit 1040 drives the transfer transistor 1031, the reset transistor 1032, and the selection transistor 1033 with the power supply voltage, the source potential of each transistor is suppressed to a voltage that is lower than the power supply voltage by the threshold voltage. Is done. Thereby, the readout amount of the photodiode charge by the transfer transistor, the source follower circuit operation range by the selection transistor, and the source follower circuit gate applied voltage by the reset transistor are suppressed. As a result, the amount of signals that can be handled is reduced, so that the dynamic range is reduced. On the other hand, when the vertical scanning unit 1040 drives the transfer transistor 1031, the reset transistor 1032, and the selection transistor 1033 with the boosted voltage supplied from the booster circuit 1100, each transistor operates using the source potential as the power supply voltage. It becomes possible. As a result, sufficient readout of the photodiode charge, output up to the power supply voltage of the source follower circuit, and application of the power supply voltage itself to the source follower circuit gate are possible, and the amount of signals that can be handled increases, so a high dynamic range Can be realized.

Further, the solid-state imaging device 1000 requires a constant voltage or a constant current input, such as an input current to the read current source 1050 in FIG. 14 and a current source for an amplifier included in the reference voltage of the booster circuit 1100 and the like. There are many circuits that do this. In particular, noise mixed in the reference voltage of the read current source 1050 affects all the columns in common and becomes so-called horizontal noise, so the influence on the image quality is very large. As a noise countermeasure for the amplifier current source included in the input voltage to the read current source 1050, the reference voltage of the booster circuit 1100, etc., a low-pass filter is provided and noise band is limited to output the noise. It is known that the constant voltage signal can be reduced in noise.

JP 2000-224495 A

In the above-described conventional solid-state imaging device, a high dynamic range can be achieved by using a booster circuit, and a low noise can be achieved by using a low-noise circuit including a low-pass filter.

However, the booster circuit is a circuit that requires time until the normal boosted voltage value is output after the booster circuit is started up, and the booster circuit reaches a level acceptable as the start-up time as the solid-state imaging device. It is necessary to shorten the startup time. On the other hand, the use of a low noise circuit limits the bandwidth of the circuit itself and delays the supply of constant voltage and constant current due to the rise delay of the low pass filter. Therefore, for example, a booster circuit to which a constant voltage is input from a low noise circuit cannot operate normally until the constant voltage is normally input. Therefore, the start-up is further delayed as a price for reducing noise. Furthermore, in order to increase the noise reduction effect by the low noise circuit, the larger the band is, the larger the capacity constituting the low-pass filter must be, and the start-up will be delayed.

In response to the recent demand for improvement in image quality performance in solid-state imaging devices and the sensitivity of unit pixel cells due to pixel miniaturization, in the adverse effect of long startup time due to the booster circuit and low noise circuit described above In order to improve SN against the decline, the need to limit noise is becoming increasingly strong. For this reason, in noise removal by band limitation, the band limitation is performed to a lower frequency, that is, the cutoff frequency that determines the noise removal lower limit frequency of the low-pass filter is set to a lower frequency, thereby increasing the noise. It is necessary to reduce.

For this reason, the startup delay of the booster circuit is steadily increasing. In order to solve the problem, it is possible to improve the driving capability and increase the starting speed by increasing the switch size of the booster circuit to reduce the resistance of the switch path or increasing the switching frequency. However, lowering the resistance of the switch path increases the inrush current during switching, and increasing the switching frequency increases the switching frequency. As a result, the switching noise itself generated by the booster circuit also increases, and the noise reduction effect of the low noise circuit is impaired. Despite start-up time delay and switching noise increase, a booster circuit is indispensable for realizing a high dynamic range, and it is impossible to select not to use a booster circuit.

As described above, the conventional solid-state imaging device has a problem that it is difficult to achieve both high-speed startup, low noise, and high dynamic range. However, there are no issues or knowledge about the relationship between noise, start-up time and dynamic range.

In view of the above problems, an object of the present invention is to provide a solid-state imaging device having a function of achieving both high-speed startup, low noise, and high dynamic range.

In order to solve the above problems, a solid-state imaging device according to one embodiment of the present invention includes a plurality of pixels that are arranged in a matrix and convert light into a signal voltage, and a vertical signal line provided for each pixel column. A current source circuit that is provided for each pixel column and supplies a current for reading the signal voltage to the vertical signal line by being supplied with a first voltage; and a power supply voltage by being supplied with a second voltage. Uses a voltage conversion circuit for generating different voltages, drives the plurality of pixels in a row sequence using the voltage generated by the voltage conversion circuit, and connects the vertical signal line and the current source circuit from the pixels in the corresponding row. A vertical scanning circuit that reads out the signal voltage via the first voltage circuit, a first constant voltage circuit that supplies the current source circuit with the first voltage from which a higher frequency component is removed than the second voltage, and the voltage conversion circuit. Supply the second voltage Characterized in that it comprises a second constant voltage circuit that.

With this configuration, the vertical scanning circuit can drive the driving voltage for driving each pixel not by the power supply voltage but by the voltage supplied by the voltage conversion circuit. Accordingly, the source potential of the transistor included in each pixel can be operated up to the power supply voltage without being suppressed to a voltage lower than the power supply voltage by the threshold voltage. As a result, since a pixel signal that sufficiently reflects the signal voltage can be output from each pixel, a high dynamic range can be achieved.

Also, the second constant voltage circuit that outputs the second voltage including the high band has a large amount of noise because the band is not limited, but the startup time as the constant voltage circuit is fast. On the other hand, the first constant voltage circuit that outputs the first voltage in the low band has a small amount of noise because the band is limited, but the start-up time is slow due to the resistors and capacitors that constitute the low-pass filter. In this regard, the generated voltage of the voltage conversion circuit is supplied for the purpose of logical operation as the switch voltage of the pixel transistor, so the contribution of noise of the generated voltage itself to the pixel output is low, so the reference voltage without band limitation Is not a big problem for the image quality.

On the other hand, noise mixed in the current source circuit for reading out the signal voltage of each pixel is largely propagated to the pixel output and greatly affects the image quality. In particular, noise mixed in the reference voltage of the current source circuit affects all the columns in common, so that it becomes so-called horizontal noise, and the influence on the image quality is very large.

With this configuration, by using the first constant voltage circuit that outputs the first voltage in the low band for supplying the reference voltage to the current source circuit, the noise amount of the reference voltage is suppressed and the noise of the pixel output is reduced. The The start-up delay of the constant voltage circuit itself increases due to the band limitation, so the delay before starting the signal voltage read operation increases, but the read operation must be started before the voltage conversion circuit starts up. For example, it does not affect the startup time of the solid-state imaging device. In this respect, the activation of the voltage conversion circuit and the first constant voltage circuit having a low bandwidth can be operated in parallel. Therefore, since the start time of the voltage conversion circuit can be used as the read operation start time, it is possible to perform sufficient band limitation on the first constant voltage circuit. Therefore, it is possible to realize low noise and high dynamic range without degrading the startup time as a solid-state imaging device.

The solid-state imaging device is further connected to the first capacitor element connected to the first constant voltage circuit and the second constant voltage circuit, and has a capacitance value different from that of the first capacitor element. 2 capacitive elements.

Thus, a low-pass filter having a different band characteristic is formed by a capacitor having a different capacitance value connected to the constant voltage circuit using the impedance of the constant voltage circuit as a resistor. In this case, a resistance element can be dispensed with. Therefore, the band limitation degree of the output voltage of the first constant voltage circuit connected to the current source circuit and the band limitation degree of the output voltage of the second constant voltage circuit connected to the voltage conversion circuit are reduced by noise and It becomes possible to make it different according to the necessity of shortening the delay time.

Further, the solid-state imaging device is further connected to the first filter circuit connected to the first constant voltage circuit and to the second constant voltage circuit, and has a higher pass band than the first filter circuit. And a second filter circuit.

Thereby, the band restriction degree of the output voltage of the first constant voltage circuit connected to the current source circuit can be set higher than the band restriction degree of the output voltage of the second constant voltage circuit connected to the voltage conversion circuit. Therefore, it is possible to enhance noise removal in the current source circuit without deteriorating the delay time.

Further, one of the first constant voltage circuit and the second constant voltage circuit is connected to a capacitive element, and the other of the first constant voltage circuit and the second constant voltage circuit is a capacitive element. May not be connected.

This contributes to the reduction in the number of circuit components, while reducing the band limitation of the output voltage of the first constant voltage circuit and the band limitation of the output voltage of the second constant voltage circuit, and reducing the delay time. It becomes possible to make it different according to the necessity of conversion.

Further, a filter circuit may be connected to the first constant voltage circuit, and a filter circuit may not be connected to the second constant voltage circuit.

This makes it possible to enhance noise removal in the current source circuit without degrading the delay time while contributing to the reduction in the number of circuit components.

In addition, the first constant voltage circuit and the second constant voltage circuit are included in a third constant voltage circuit, and the third constant voltage circuit includes components of the first constant voltage circuit and A part of the components of the second constant voltage circuit is shared, and the first voltage from the first constant voltage circuit and the second voltage from the second constant voltage circuit are independently output. May be.

This makes it possible to supply a constant voltage to the voltage conversion circuit and a constant voltage to the current source circuit from a single low voltage circuit. For example, the constant voltage to the voltage conversion circuit is output via the constant voltage circuit unit included in the third constant voltage circuit, and the constant voltage to the current source circuit is output from the constant voltage circuit unit included in the third constant voltage circuit. And output through a band limiting resistor. Therefore, it is possible to achieve both high-speed startup, low noise, and high dynamic range while realizing a reduction in circuit scale.

In order to solve the above problems, a solid-state imaging device according to one embodiment of the present invention includes a plurality of pixels arranged in a matrix and converting light into a signal voltage, and a plurality of pixels provided for each pixel column. A vertical signal line, a current source circuit that is provided for each pixel column, supplies a current for reading the signal voltage to the vertical signal line by supplying a first current, and a second current is supplied. A voltage conversion circuit that generates a voltage different from the power supply voltage, and the plurality of pixels are driven in a row sequence using the voltage generated by the voltage conversion circuit, and the vertical signal lines and the pixels from the pixels in the corresponding row are driven. A vertical scanning circuit that reads out the signal voltage via a current source circuit; a first constant current circuit that supplies the first current from which a high-frequency component is removed from the second current to the current source circuit; and the voltage In the conversion circuit, the first Characterized in that it comprises a second constant current circuit for supplying a current.

With this configuration, as described above, since a pixel signal that sufficiently reflects the signal voltage can be output from each pixel, a high dynamic range can be achieved.

Also, the second constant current circuit has a large amount of noise, but the startup time is fast. On the other hand, the first constant current circuit has a small amount of noise but a low startup time. In this regard, since the contribution of noise generated by the voltage conversion circuit itself to the pixel output is low, even if a reference current that is not band-limited is supplied, it does not pose a significant problem in image quality.

On the other hand, noise mixed in the current source circuit for reading out the signal voltage of each pixel is largely propagated to the pixel output and greatly affects the image quality. In particular, noise mixed in the reference current of the current source circuit affects all columns in common, so that it becomes so-called horizontal noise, and the influence on image quality is very large.

With this configuration, by using the first constant current circuit that outputs the first current in the low band for supplying the reference current to the current source circuit, the noise amount of the reference current is suppressed and the noise of the pixel output is reduced. The Due to the band limitation, the startup delay of the constant current circuit itself increases, so the delay until the signal voltage read operation starts increases, but the read operation must be started before the voltage conversion circuit starts. For example, it does not affect the startup time of the solid-state imaging device. In this respect, the activation of the voltage conversion circuit and the first constant current circuit having a low bandwidth can be operated in parallel. Therefore, since the startup time of the voltage conversion circuit can be used for the read operation startup time, it is possible to perform sufficient band limitation on the first constant current circuit. Therefore, it is possible to realize low noise and high dynamic range without degrading the startup time as a solid-state imaging device.

Also, a mirror circuit is configured to supply a reference current instead of a reference voltage to the current source circuits in each column. With this configuration, noise propagation to the pixel output when the source potential of the current source circuit fluctuates due to noise or the like is suppressed.

The solid-state imaging device is further connected to the first capacitor element connected to the first constant current circuit and the second constant current circuit, and has a capacitance value different from that of the first capacitor element. 2 capacitive elements.

Thus, a low-pass filter having a different band characteristic is formed with a capacitor having a different capacitance value connected to the constant current circuit, using the impedance of the constant current circuit as a resistance. In this case, a resistance element can be dispensed with. Accordingly, the band limitation degree of the output voltage of the first constant current circuit connected to the current source circuit and the band limitation degree of the output voltage of the second constant current circuit connected to the voltage conversion circuit are reduced by noise and It becomes possible to make it different according to the necessity of shortening the delay time.

The solid-state imaging device further includes a first filter circuit connected to the first constant current circuit, and a second pass filter connected to the second constant current circuit, and having a higher passband than the first filter circuit. And a second filter circuit.

Thereby, the band limit degree of the output voltage of the first constant current circuit connected to the current source circuit can be set higher than the band limit degree of the output voltage of the second constant current circuit connected to the voltage conversion circuit. Therefore, it is possible to enhance noise removal in the current source circuit without deteriorating the delay time.

Further, one of the first constant current circuit and the second constant current circuit is connected to a capacitor element, and the other of the first constant current circuit and the second constant current circuit is a capacitor element. May not be connected.

Thereby, while contributing to the reduction of the number of circuit components, the band limitation degree of the output voltage of the first constant current circuit and the band limitation degree of the output voltage of the second constant current circuit are reduced by noise and the delay time is shortened. It becomes possible to make it different according to the necessity of conversion.

Further, a filter circuit may be connected to the first constant current circuit, and a filter circuit may not be connected to the second constant current circuit.

Further, at least one of the first constant current circuit and the second constant current circuit may be a constant current circuit that generates a current by dividing a voltage.

The first constant current circuit includes a fourth constant voltage circuit and a first voltage / current conversion circuit, and the second constant current circuit includes the fourth constant voltage circuit and the second voltage. The first constant current circuit and the second constant current circuit are included in a third constant current circuit, and the third constant current circuit includes the first constant current circuit. The circuit and the second constant voltage circuit share the fourth constant voltage circuit, and the first constant current from the first constant current circuit and the second current from the second constant current circuit And may be output independently.

This makes it possible to supply a constant current to the voltage conversion circuit and a constant current to the current source circuit from a single constant current circuit. For example, the constant current to the voltage conversion circuit is output via the third constant voltage circuit and the second voltage current conversion circuit, and the constant current to the current source circuit is the third constant voltage circuit and the first voltage conversion circuit. The output is made via a voltage-current conversion circuit. Therefore, it is possible to achieve both high-speed startup, low noise, and high dynamic range while realizing a reduction in circuit scale.

The solid-state imaging device is further connected to the third capacitor element connected to the first voltage-current converter circuit and to the second voltage-current converter circuit, and the capacitance value of the third capacitor element is A different fourth capacitor element may be provided.

Thus, a low-pass filter having a different band characteristic is formed by a capacitive element having a different capacitance value connected to the voltage-current converter circuit, using the impedance of the voltage-current converter circuit as a resistor. In this case, a resistance element can be dispensed with. Therefore, the band limitation degree of the output voltage of the first voltage-current conversion circuit connected to the current source circuit and the band limitation degree of the output voltage of the second voltage-current conversion circuit connected to the voltage conversion circuit are expressed as noise. It becomes possible to make it different according to the necessity of removal and delay time shortening.

The solid-state imaging device further includes a third filter circuit connected to the first voltage-current conversion circuit and a second filter-current conversion circuit connected to the second voltage-current conversion circuit and having a higher pass than the third filter circuit. And a fourth filter circuit having a band.

Thereby, the band limitation degree of the output current of the first voltage-current conversion circuit connected to the current source circuit is set higher than the band limitation degree of the output current of the second voltage-current conversion circuit connected to the voltage conversion circuit. it can. Therefore, it is possible to enhance noise removal in the current source circuit without deteriorating the delay time.

One of the first voltage-current conversion circuit and the second voltage-current conversion circuit is connected to a capacitive element, and the other of the first voltage-current conversion circuit and the second voltage-current conversion circuit. May not be connected to the capacitor.

Thereby, while contributing to the reduction in the number of circuit components, the band limitation degree of the output current of the first voltage-current converter circuit and the band limit degree of the output current of the second voltage-current converter circuit are reduced with noise and delayed. It becomes possible to make it different according to the necessity of time reduction.

Further, a filter circuit may be connected to the first voltage-current conversion circuit, and a filter circuit may not be connected to the second voltage-current conversion circuit.

According to the solid-state imaging device of the present invention, (1) a vertical scanning circuit drives each pixel with a voltage supplied from a voltage conversion circuit instead of a power supply voltage, and (2) a voltage having a high frequency component is converted into a voltage. Since the voltage supplied to the circuit and limited to the frequency component in the low band is supplied to the current source circuit, it is possible to achieve both low noise and high dynamic range without degrading the startup time as a solid-state imaging device. Is possible.

FIG. 1 is a block diagram showing a configuration of a solid-state imaging device 1 according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing an example of the configuration of the unit pixel 5 and the vertical scanning circuit 40 included in the solid-state imaging device of the present invention. FIG. 3 is a block diagram showing an example of the configuration of the column ADC 56 included in the solid-state imaging device of the present invention. FIG. 4 is a block diagram illustrating an example of the configuration of the voltage conversion circuit 300 included in the solid-state imaging device of the present invention. FIG. 5A is a block diagram illustrating an example of a configuration of the low-band constant voltage circuit 100 included in the solid-state imaging device 1 according to Embodiment 1 of the present invention. FIG. 5B is a block diagram illustrating an example of a configuration of the high-band constant voltage circuit 200 included in the solid-state imaging device 1 according to Embodiment 1 of the present invention. FIG. 6 is a block diagram showing a configuration of the solid-state imaging device 2 according to Embodiment 2 of the present invention. FIG. 7A is a block diagram illustrating a first example of the configuration of the low-band constant current circuit 107 included in the solid-state imaging device 2 according to Embodiment 2 of the present invention. FIG. 7B is a block diagram illustrating a first example of the configuration of the high-band constant current circuit 207 included in the solid-state imaging device 2 according to Embodiment 2 of the present invention. FIG. 8A is a block diagram illustrating a second example of the configuration of the low-band constant current circuit 107 included in the solid-state imaging device 2 according to Embodiment 2 of the present invention. FIG. 8B is a block diagram illustrating a second example of the configuration of the high-band constant current circuit 207 included in the solid-state imaging device 2 according to Embodiment 2 of the present invention. FIG. 9A is a block diagram showing a third example of the configuration of the low-band constant current circuit 107 included in the solid-state imaging device 2 according to Embodiment 2 of the present invention. FIG. 9B is a block diagram illustrating a third example of the configuration of the high-band constant current circuit 207 included in the solid-state imaging device 2 according to Embodiment 2 of the present invention. FIG. 10 is a block diagram showing a configuration of the solid-state imaging device 3 according to Embodiment 3 of the present invention. FIG. 11 is a block diagram showing a configuration of a multiband constant voltage circuit 400 included in the solid-state imaging device 3 according to Embodiment 3 of the present invention. FIG. 12 is a block diagram showing a configuration of the solid-state imaging device 4 according to Embodiment 4 of the present invention. FIG. 13 is a block diagram showing a configuration of a multiband constant current circuit 407 included in the solid-state imaging device 4 according to Embodiment 4 of the present invention. FIG. 14 is a block diagram illustrating a configuration of a conventional solid-state imaging device 1000 disclosed in Patent Document 1. In FIG.

(Embodiment 1)
Hereinafter, the configuration and operation of the solid-state imaging device 1 according to Embodiment 1 of the present invention will be described with reference to the drawings.

The solid-state imaging device 1 according to the present embodiment includes a low-band constant voltage circuit that limits the band in order to reduce noise, and a high-band low-voltage circuit that does not limit the band for speeding up the start. By supplying the voltage circuit to at least the readout current source of the pixel source follower circuit and supplying the high-band low-voltage circuit to at least the voltage conversion circuit, both high-speed startup, low noise, and high dynamic range are achieved. To do.

FIG. 1 is a block diagram showing a configuration of a solid-state imaging device 1 according to Embodiment 1 of the present invention. The solid-state imaging device 1 illustrated in FIG. 1 includes a pixel array 10, a vertical scanning circuit 40, a plurality of transfer transistor control lines 41, a plurality of reset transistor control lines 42, a plurality of selection transistor control lines 43, A plurality of vertical signal lines 45, a plurality of read current sources 50, a plurality of column ADCs 56, a reference signal generator 57, a horizontal signal line 55, a horizontal scanning circuit 60, a plurality of horizontal control lines 65, and an output A circuit 67, a timing control unit 70, at least one high-band constant voltage circuit 200, at least one low-band constant voltage circuit 100, and a band limiting capacitor 101 for limiting the band of the low-band constant voltage circuit; And at least one voltage conversion circuit 300.

Each functional block shown in FIG. 1 is arranged on only one side when viewed from the pixel array 10, but may be arranged on both sides of the pixel array 10.

The pixel array 10 includes a plurality of unit pixels 5 arranged in a matrix, and the unit pixels 5 photoelectrically convert the received light into signal voltages. The plurality of vertical signal lines 45 are provided corresponding to the columns of the unit pixels 5 and transmit the signal voltages output from the unit pixels 5 of the corresponding columns.

FIG. 2 is a block diagram showing an example of the configuration of the unit pixel 5 and the vertical scanning circuit 40 included in the solid-state imaging device of the present invention.

The unit pixel 5 is a so-called four-transistor unit pixel cell, and includes a photodiode 30, a transfer transistor 31, a reset transistor 32, a selection transistor 33, and a readout transistor 34 (hereinafter collectively referred to as a pixel transistor). It is a pixel provided.

The read transistor 34 is connected in common by a vertical signal line 45 provided for each column between a plurality of unit pixels arranged in the same column, and a read current source 50 which is a current source circuit provided for each pixel column. A source follower circuit (hereinafter referred to as a pixel source follower) is constituted by the read transistor 34 in the row in which the selection transistor 33 is conducted. The pixel signal is read out by the pixel source follower via the vertical signal line 45.

In the present embodiment, the 4-transistor type unit pixel 5 is illustrated, but the unit pixel 5 may be a so-called 3-transistor type unit pixel in which the selection transistor 33 does not exist, and a plurality of photodiodes. 30 may be a unit pixel of a so-called multi-pixel 1 cell sharing the readout transistor 34. Each transistor constituting the unit pixel 5 may be either an NMOS transistor or a PMOS transistor, and a plurality of vertical signal lines 45 may exist for one column. Further, the unit pixel 5 is not limited to the configuration shown in FIG. 2 as long as the signal voltage from the photodiode 30 can be output to the vertical signal line 45.

The vertical scanning circuit 40 includes a decoder 44 that determines which row of pixel signals to read based on information from the timing control unit 70, and a plurality of vertical drivers 47 that drive each pixel transistor in the pixel. The In this embodiment, the vertical driver 47 has the same configuration as each pixel transistor. However, at least one vertical driver 47 supplies a boosted voltage only to the vertical driver 47 that drives the reset transistor control line 42. As long as the voltage from the voltage conversion circuit 300 is supplied to the driver 47, it does not depart from the object and scope of the present invention. Further, different voltages from a plurality of voltage conversion circuits 300 are supplied to one vertical driver 47, such as a boosted voltage as an H level and a negative stepped down voltage as an L level are supplied to the vertical driver 47. However, it does not depart from the object and scope of the present invention.

The vertical scanning circuit 40 sequentially activates the transfer transistor control line 41, the reset transistor control line 42, and the selection transistor control line 43 to sequentially select the rows of the unit pixels 5 and perform vertical scanning. The signal voltage of the selected row is transmitted to the column ADC 56 via the pixel source follower for each column.

For example, in the unit pixel 5 in the m-th row, first, the reset transistor 32 is turned on by the reset transistor control line 42, whereby the gate voltage of the read transistor 34, that is, the so-called floating diffusion voltage is reset.

Subsequently, the selection transistor 33 is turned on by the selection transistor control line 43, and the voltage after resetting the floating diffusion portion is set as the reset level voltage Vrst of the unit pixel 5 in the m-th row through the readout transistor 34 and the vertical signal line 45. And supplied to the column ADC 56 at the subsequent stage for AD conversion.

Subsequently, the photodiode 30 accumulates charges obtained by photoelectrically converting light received during the exposure time. After the predetermined exposure time, the transfer transistor 31 is turned on in the unit pixel 5 in the m-th row by the transfer transistor control line 41, and the charge accumulated in the photodiode 30 is transferred to the floating diffusion portion. The transferred charge is vertically transmitted through the read transistor 34 as a voltage (Vrst + Vsig) obtained by superimposing the voltage Vsig of the m-th row signal level corresponding to the amount of received light on the reset level voltage Vrst of the unit pixel 5 of the m-th row. The signal is output to the signal line 45 and supplied to the subsequent column ADC 56 for AD conversion. Thus, the signal level of the unit pixel 5 in the m-th row corresponding to the amount of received light can be obtained by a so-called double sampling operation that extracts a difference between signals generated as a result of two AD conversions.

Note that the driving method of the unit pixel 5 described above is an example. The object and scope of the present invention do not limit the processing of the pixel signal, but the reset level voltage Vrst of the m-th unit pixel 5 and the m-th row signal level voltage Vsig according to the m-th received light amount. Is not limited to the illustrated driving method. Further, there may be a driving method in which the column ADC 56 does not exist and the conversion is performed by a single ADC after horizontal selection as an analog signal as in the conventional solid-state imaging device illustrated in FIG.

In the solid-state imaging device 1 shown in FIG. 1, no signal amplifying means is provided for the output of the unit pixel 5, but an AGC (Auto) is provided in the signal path from the output of the unit pixel 5 to the input of the column ADC 56. A signal amplifying means such as Gain Control), a so-called column amplifier may be provided. In this case, the signal level of the signal input to the column ADC 56 can be increased. As a result, the input conversion S / N in AD conversion is improved, and the image quality of the solid-state imaging device 1 can be improved. it can. As the column amplifier, a so-called single-ended inverter amplifier that drives a constant-current load with a source-grounded amplifier circuit is preferably used. Amplifying means such as an amplifier circuit may be used. Further, a sample hold means for sample holding the signal input to the column ADC 56 may be provided. In the case where sample hold means for the signal input to the column ADC 56 is provided, it is possible to perform so-called pipeline operation in which the conversion operation of the column ADC 56 and the signal reading from the unit pixel 5 to the vertical signal line 45 are operated in parallel. As a result, the frame rate of the solid-state imaging device 1 can be improved.

FIG. 3 is a block diagram showing an example of the configuration of the column ADC 56 included in the solid-state imaging device of the present invention.

The column ADC 56 is provided corresponding to the vertical signal line 45, and converts the signal voltage transmitted through the corresponding vertical signal line 45 into a digital signal. The reference signal generation unit 57 generates a common reference signal supplied to the column ADC 56 of each column.

Next, the configuration of the column ADC 56 and the AD conversion operation will be described with reference to FIG.

In the present embodiment, the column ADC 56 is exemplified as a so-called single slope AD converter circuit, but other ADC methods such as successive approximation do not depart from the object and scope of the present invention. The column ADC 56 in the present embodiment simultaneously converts a plurality of signal voltages output to the vertical signal lines 45 of each column into digital signals.

The column ADC 56 includes a voltage comparison unit 415, a count unit (counter) 416, and a memory unit 418, and a common reference signal from the reference signal generation unit 57 is input thereto.

The reference signal generator 57 generates a reference signal voltage (ramp waveform signal voltage) Vslope that gradually changes over time. The reference signal voltage Vslope may be a smooth slope waveform or a stepped waveform, and the waveform is not particularly limited as long as the waveform changes with a certain slope. Similarly, the slope of the reference signal voltage Vslope may be either positive or negative. The reference signal generation unit 57 can be configured by filtering the DAC output by giving a code value that increases or decreases to a DAC (digital analog converter), or by performing an integration operation using a capacitive element. This configuration is not particularly limited as long as it is a reference signal generation unit 57 that can generate a waveform that changes with a certain inclination.

The voltage comparison unit 415 compares the signal voltage output to the vertical signal line 45 and converted into a digital signal with the reference signal voltage Vslope that is input to the voltage comparison unit 415 and gradually changes. The voltage comparison unit 415 is preferably composed of a differential comparator having a well-known offset cancellation function, but may be composed of a so-called chopper comparator or the like, and the signal voltage of the vertical signal line 45 and the reference The configuration is not particularly limited as long as the voltage comparison unit 415 can compare the signal voltage Vslope.

The counting unit 416 changes the time from when the voltage comparison unit 415 starts comparison until the comparison result of the voltage comparison unit 415 changes, that is, the magnitude relationship between the signal voltage of the vertical signal line 45 and the reference signal voltage Vslope. A / D conversion is performed by counting the time until the output of the voltage comparison unit 415 is inverted. That is, the count unit 416 performs AD conversion by counting the input clock CLK from the start of comparison until the magnitude relationship between the signal voltage and the reference signal voltage Vslope changes. After the AD conversion is completed, the count unit 416 transmits the digital signal value (count value) to the memory unit 418, and the memory unit 418 stores the transmitted digital signal value. This AD conversion is performed twice on the reset level voltage Vrst and the voltage (Vrst + Vsig) obtained by superimposing the reset level Vrst on the signal level voltage Vsig corresponding to the amount of received light. The signal of the unit pixel 5 is obtained from the difference information. A level is obtained. This double sampling operation is not essential for the present invention, and even if AD conversion is performed only for the signal level Vsig, it does not depart from the object and scope of the present invention.

The horizontal scanning circuit 60 sequentially controls the horizontal control lines 65 based on information from the timing control unit 70. As a result, the digital signal value stored in the memory unit 418 for each column is read to the horizontal signal line 55 and supplied to the output circuit 67.

The output circuit 67 outputs the transmitted digital signal value to the outside. A high-speed transmission circuit such as LVDS is preferably used as the output circuit 67, but the output method, circuit, and configuration of the output circuit 67 are not particularly limited as long as the output means can output a digital signal value. Further, the type of serial output and parallel output, the number of output ports, and the like are not particularly limited.

The feature of the solid-state imaging device 1 according to the present embodiment is that it includes at least one high-band constant voltage circuit 200, at least one low-band constant voltage circuit 100, and at least one voltage conversion circuit 300.

With this configuration, the vertical scanning circuit 40 can drive the gate drive HIGH levels of the transfer transistor 31, the reset transistor 32, and the selection transistor 33 with the boosted voltage supplied from the voltage conversion circuit 300 instead of the power supply voltage. . Therefore, the source potential of each transistor can be operated up to the power supply voltage without being suppressed to a voltage lower than the threshold voltage from the power supply voltage. As a result, sufficient readout of the photodiode charge, output up to the power supply voltage of the source follower circuit, and application of the power supply voltage itself to the source follower circuit gate become possible, and the amount of signals that can be handled increases, resulting in a high dynamic range. Is possible.

Further, the vertical scanning circuit 40 can drive the gate drive LOW level of the transfer transistor 31, the reset transistor 32, and the selection transistor 33 with a negative step-down voltage supplied from the voltage conversion circuit 300, instead of the ground potential. . Therefore, the gate potential when each transistor is turned off becomes a negative step-down voltage, and the occurrence of off-leakage current in each pixel transistor is suppressed, and abnormalities such as scratches and floating as an image are suppressed, thereby achieving high image quality.

As described above, by using at least one voltage conversion circuit 300 to generate a boosted voltage higher than the power supply voltage or a negative stepped-down voltage, supply it to the vertical scanning circuit 40, and use it for driving the pixel transistor, high dynamics can be achieved. Range and high image quality are realized.

FIG. 4 is a block diagram showing an example of the configuration of the voltage conversion circuit 300 included in the solid-state imaging device of the present invention. The voltage conversion circuit 300 shown in the figure is a so-called charge pump type booster circuit, and includes switches SW1 to SW4, a pump capacitor Cp, a smoothing capacitor Cout, a voltage dividing resistor R1 for detecting a generated voltage, and R2 and a comparison circuit 301 that detects the generated voltage and controls the boosting operation.

The voltage conversion circuit 300 repeats the operation of accumulating energy as a voltage in the pump capacitor Cp and the operation of transferring the energy to the smoothing capacitor Cout by the switching operation of the switches SW1 to SW4, thereby increasing the voltage higher than the power supply voltage. Is generated. In the present embodiment, the switches SW1 and SW3 are turned on when energy is stored in the pump capacitor Cp, and the switches SW2 and SW4 are turned on when the energy is transferred to the smoothing capacitor Cout.

The comparison circuit 301 controls the switching operation so that the generated voltage becomes a desired voltage, and generates a desired voltage different from the power supply voltage. In the present embodiment, when the detection voltage by the voltage dividing resistors R1 and R2 exceeds the input reference voltage, the output of the comparison circuit 301 is inverted and the CLK input for switching operation is gated. Thereby, the switching operation is stopped, and the generated voltage becomes a desired voltage value.

The voltage conversion circuit 300 may be a step-up circuit or a negative step-down circuit, and may be a so-called charge pump type circuit or a switching regulator type circuit. Not deviate from.

Generally, the voltage conversion circuit 300 requires at least one of a reference voltage and a reference current. In this embodiment, the comparison circuit 301 requires a reference voltage for voltage comparison and a reference current for circuit operation of the comparison circuit.

5A and 5B are block diagrams showing examples of configurations of the high-band constant voltage circuit 200 and the low-band constant voltage circuit 100 included in the solid-state imaging device 1 according to Embodiment 1 of the present invention, respectively. In the present embodiment, the solid-state imaging device 1 includes at least one high-band constant voltage circuit 200 and at least one low-band constant voltage circuit 100.

The high band constant voltage circuit 200 is a second constant voltage circuit that outputs a second voltage with no band limitation to the output of a general band gap reference circuit (BGR in the figure) 105. On the other hand, the low-band constant voltage circuit 100 performs band limitation by inserting a low-pass filter 103 including a band-limiting resistor 102 and a band-limiting capacitor 101 with respect to the output of a general band-gap reference circuit 105 to perform first band limitation. It is the 1st constant voltage circuit which outputs a voltage. Since the high-band constant voltage circuit 200 is not band-limited, the amount of noise is large, but the startup time as the constant-voltage circuit is fast. On the other hand, since the low-band constant voltage circuit 100 performs band limitation, the amount of noise is small and the low-band voltage circuit 100 can be used as a low-noise circuit. Time is slow.

For the band limiting capacitor 101, it is preferable to use an external capacitor in order to greatly limit the band. However, it is not always necessary to use an external capacitor. The use of this capacity does not depart from the purpose and scope of the present invention. In the present embodiment, the band gap reference circuit 105 is exemplified. However, if the voltage source circuit generates a voltage, the object and scope of the present invention are applicable to, for example, a voltage generation circuit using resistance voltage division. Not deviate from. Furthermore, in the present embodiment, an example in which the low-pass filter 103 that is the first filter circuit is connected only to the low-band constant voltage circuit 100 is illustrated. However, the high-band constant voltage circuit 200 is not affected by the startup time. Even if a low-pass filter, which is the second filter circuit, is connected, it does not depart from the object and scope of the present invention. In this case, the band of the low pass filter connected to the low band constant voltage circuit 100 is set lower than the band of the low pass filter connected to the high band constant voltage circuit 200. In addition, it is not always necessary to perform band limitation using a low-pass filter, and band limitation by another band limiting unit may be used. In addition, a low-pass filter is not configured with a band-limiting resistor and a band-limiting capacitor, but even when only a capacitive element for band-limiting is connected, the circuit output impedance of the previous stage of the band-limiting capacitor is used as a resistor, Therefore, the same effect as in the present embodiment can be obtained, and a resistance element can be dispensed with. Even in this case, not only the first capacitive element is connected to the low-band constant voltage circuit 100 but also the first capacitive element and the capacitance value are connected to the high-band constant voltage circuit 200 within a range that does not affect the startup time. Even the configuration in which the second capacitive elements having different values are connected does not depart from the object and scope of the present invention. In this case, the band of the low-pass filter composed of the first capacitor element is set lower than the band of the low-pass filter composed of the second capacitor element. Further, the number of voltage outputs is not limited, and there may be an arbitrary number of voltage outputs of 2 or more.

The voltage conversion circuit 300 requires a start-up time because it has a large capacity for smoothing and it is necessary to repeat the switching operation in order to perform the step-up or step-down operation. In the solid-state imaging device 1, the allowable time as the activation time varies depending on the application, such as several tens of ms to several hundred ms, but there is always a limitation of an allowable activation delay time. Since normal imaging cannot be performed until the voltage conversion circuit 300 is activated, the activation delay of the voltage conversion circuit 300 needs to be suppressed within a range that does not affect the above-described restriction. The startup delay of the voltage conversion circuit 300 is determined by the time required for the step-up or step-down operation and the time until the reference voltage and the reference current are normally supplied.

In the present embodiment, since the high-band constant voltage circuit 200 is used for supplying the reference voltage to the voltage conversion circuit 300, the start-up delay of the constant voltage circuit itself is small, and the start-up of the voltage conversion circuit 300 is low-band constant. The speed is increased compared to the case where the voltage circuit 100 is used. Since the startup of the voltage conversion circuit 300 is speeded up, there is a margin in the startup time, so that the voltage conversion circuit 300 reduces the switch size, increases the resistance of the switch path, or decreases the switching frequency. Is also possible. In this case, the inrush current at the time of switching is reduced and the switching frequency is lowered, so that the switching noise itself generated by the booster circuit is also reduced, and the noise can be further reduced. The generated voltage of the voltage conversion circuit 300 is supplied as a switch voltage of the pixel transistor for the purpose of logical operation, and the voltage conversion circuit 300 itself forms one band limit, so that noise of the generated voltage itself propagates to the pixel output. Since the degree of contribution is low, supplying a reference voltage and a reference current that are not band-limited does not pose a major problem in image quality.

On the other hand, the noise mixed in the pixel source follower composed of the read current source 50 and the read transistor 34 is largely propagated to the pixel output and greatly affects the image quality. In particular, noise mixed in the reference voltage of the read current source 50 affects all the columns in common, so that it becomes so-called horizontal noise, and the influence on the image quality is very large. Therefore, the reference voltage to the read current source 50 needs to greatly limit noise.

In this embodiment, by using the low-band constant voltage circuit 100 to supply the reference voltage to the read current source 50, the amount of noise of the reference voltage is suppressed, and the noise of the pixel output is reduced. In addition, due to the band limitation, the startup delay of the constant voltage circuit itself is large and the delay until the operation of the pixel source follower is increased. However, the pixel source follower has been started up before the voltage conversion circuit 300 is started up. For example, it does not affect the startup time of the solid-state imaging device 1. In this regard, the activation of the voltage conversion circuit 300 and the low-band constant voltage circuit 100 can be operated in parallel. Therefore, the start time of the voltage conversion circuit 300 and the same start time such as several tens ms to several hundred ms can be given to the pixel source follower, so that sufficient band limitation is performed on the low band constant voltage circuit 100. It becomes possible. Therefore, noise can be greatly reduced without degrading the startup time of the solid-state imaging device 1.

As described above, the solid-state imaging device 1 according to the present embodiment includes at least one high-band constant voltage circuit 200 and converts at least the voltage conversion circuit 300 using the second voltage generated by the high-band constant voltage circuit 200. Used in. In addition, the solid-state imaging device 1 includes at least one low-band constant voltage circuit 100 and uses at least the read current source 50 with the first voltage generated by the low-band constant voltage circuit 100. As a result, it is possible to achieve both a start-up time as the solid-state imaging device 1 and a reduction in noise and a high dynamic range.

(Embodiment 2)
Hereinafter, the configuration and operation of the solid-state imaging device 2 according to Embodiment 2 of the present invention will be described with reference to the drawings. Hereinafter, only differences from the solid-state imaging device 1 according to Embodiment 1 will be described.

The solid-state imaging device 2 according to the present embodiment is different from the solid-state imaging device 1 according to the first embodiment in that a low-band constant current circuit and a high-band constant voltage circuit are used instead of the low-band constant voltage circuit and the high-band constant voltage circuit. Use of the current circuit is different. Further, the difference is that the gate input to the read current source 50 which is a current source circuit is not a reference voltage, the read current source 50 forms a mirror circuit, and the reference current becomes an input to the read current source 50.

FIG. 6 is a block diagram showing a configuration of the solid-state imaging device 2 according to Embodiment 2 of the present invention. 7A and 7B are block diagrams showing first examples of the configurations of the low-band constant current circuit 107 and the high-band constant current circuit 207, respectively, included in the solid-state imaging device 2 according to Embodiment 2 of the present invention. It is. In addition, the same code | symbol is attached | subjected about the element similar to FIG. The solid-state imaging device 2 has the same configuration as that of the solid-state imaging device 1 according to the first embodiment, except for the input unit to the low-band constant current circuit 107, the high-band constant current circuit 207, and the readout current source 50. .

In the present embodiment, the high-band constant current circuit 207 outputs the current obtained by the VI conversion circuit 500 as the second current without band limitation with respect to the output of the general bandgap reference circuit 105. It is a constant current circuit. On the other hand, the low-band constant current circuit 107 limits the band obtained by the VI conversion circuit 500 to the output of the general band gap reference circuit 105 by the band-limiting capacitor 101 and outputs it as the first current. The first constant current circuit. Note that the connection method between the VI conversion circuit 500 and the band limiting capacitor 101 exemplified in this embodiment is an example, and the configuration of the VI conversion circuit 500 is not limited as long as the circuit has a VI conversion function. For example, a simple source grounding circuit may be used. Further, if the band of the output current of the VI conversion circuit 500 is limited, the band limiting method of the VI conversion circuit is not limited. For example, the filter circuit may be configured or connected in the VI conversion circuit instead of the connection of the band limiting capacitor. Further, the number of current outputs is not limited, and there may be an arbitrary number of current outputs of two or more.

The high-band constant current circuit 207 has a large amount of noise because the band is not limited, but the startup time as a constant-current circuit is fast. On the other hand, since the low-band constant current circuit 107 performs band limitation, the amount of noise is small, and the low-band constant current circuit 107 can be used as a low-noise circuit. Is slow.

For the band limiting capacitor 101, it is preferable to use an external capacitor in order to greatly limit the band. However, it is not always necessary to use an external capacitor. The use of this capacity does not depart from the purpose and scope of the present invention. In the present embodiment, the band gap circuit is exemplified as the previous stage of the VI conversion circuit. However, the present invention is applicable to a voltage generation circuit that generates a voltage, for example, a voltage generation circuit using resistance voltage division. Does not deviate from the purpose and scope of In the present embodiment, an example in which the band limiting capacitor 101 as the first capacitor is connected only to the low-band constant current circuit 107 is illustrated. However, the high-band constant current circuit 207 is not affected by the start-up time. Even if the band limiting capacitor which is the second capacitor element is connected, it does not depart from the object and scope of the present invention. In this case, the band limiting capacity connected to the low band constant current circuit 107 is set larger than the band limiting capacity connected to the high band constant current circuit 207. Even when the band is limited by configuring or connecting the filter circuit in the VI conversion circuit, not only the first filter circuit is connected to the low-band constant current circuit 107 but also the start-up time is not affected. A second filter circuit may be connected to the high-band constant current circuit 207 in the range. Also in this case, the band limiting capacity connected to the low band constant current circuit 107 is set larger than the band limiting capacity connected to the high band constant current circuit 207.

8A and 8B are block diagrams illustrating a second example of the configuration of the low-band constant current circuit 107 and the high-band constant current circuit 207, respectively, included in the solid-state imaging device 2 according to Embodiment 2 of the present invention. . Here, the high-band constant current circuit 207 and the low-band constant current circuit 107 do not use the band gap reference circuit 105 and the VI conversion circuit 500, but a voltage dividing circuit 701 as illustrated in FIGS. 8A and 8B. Even if the current is generated by dividing the power supply voltage by using, it does not depart from the present invention.

It is also possible to generate a current by dividing an arbitrary fixed voltage instead of dividing the power supply voltage.

Even when the current is generated by dividing the fixed voltage, the low-band constant current circuit 107 can be configured by the band-limiting capacitor 705.

In FIG. 8A, an example in which the band is limited by the band limiting capacitor 705 is illustrated, but band limiting may be performed by another means such as inserting a filter circuit in the gate voltage. If the band is higher than that of the low-band constant current circuit 107, the present invention does not depart from the present invention even if the band is limited.

9A and 9B are block diagrams showing a third example of the configuration of the low-band constant current circuit 107 and the high-band constant current circuit 207, respectively, included in the solid-state imaging device 2 according to Embodiment 2 of the present invention. . 8A and 8B exemplify the example in which the voltage is divided by the resistor and the MOS transistor, but the voltage dividing circuit does not depart from the present invention as long as the requirement of current generation by dividing the fixed voltage is satisfied. For example, as shown in FIGS. 9A and 9B, voltage is divided by other means such as dividing by two MOS transistors connected in series, and a current is generated from a fixed voltage such as a power supply voltage. However, it does not depart from the present invention.

As described above, the voltage conversion circuit 300 requires a startup time, and normal imaging cannot be performed until the voltage conversion circuit 300 is started. Therefore, the startup delay of the voltage conversion circuit 300 is the startup of the solid-state imaging device 2. It is necessary to limit to a range that does not affect the time constraint.

In this embodiment, since the high-band constant current circuit 207 is used for supplying the reference current to the voltage conversion circuit 300, the start-up delay of the constant-current circuit itself is small, and the start-up of the voltage conversion circuit 300 is performed by the low-band constant current circuit. Compared with the case of using 107, the speed is increased. As described above, since the startup of the voltage conversion circuit 300 is accelerated, it is possible to reduce the inrush current at the time of switching and to reduce the switching frequency, and to reduce the switching noise itself generated by the booster circuit. Noise can be reduced. As described above, the generated voltage of the voltage conversion circuit 300 is not a big problem even if a reference voltage and a reference current that are not band-limited are supplied, but noise mixed in the pixel source follower is not output to the pixel output. Propagation greatly affects the image quality.

In the present embodiment, by using the low-band constant current circuit 107 for supplying the reference current to the read current source 50, the noise amount of the reference current is suppressed and the noise of the pixel output is reduced. In addition, due to the band limitation, the startup delay of the constant current circuit itself is large, and the delay until the operation of the pixel source follower is large. In this regard, the activation of the voltage conversion circuit 300 and the low-band constant current circuit 107 can be operated in parallel, and the activation time such as several tens ms to several hundreds ms, which is the same as the activation time of the voltage conversion circuit 300, is set as the pixel source follower. Can be given to. Therefore, sufficient band limitation can be performed on the low-band constant current circuit 107, and noise can be greatly reduced without deteriorating the startup time of the solid-state imaging device 2.

As described above, the solid-state imaging device 2 according to the present embodiment includes at least one high-band constant current circuit 207, and at least the voltage conversion circuit 300 converts the second current generated by the high-band constant current circuit 207. Used in. The solid-state imaging device 2 includes at least one low-band constant current circuit 107 and uses at least the read current source 50 the first current generated by the low-band constant current circuit 107. As a result, it is possible to achieve both a start-up time as the solid-state imaging device 2 and a low noise and high dynamic range.

In addition, by forming a mirror circuit to supply a reference current instead of a reference voltage to the pixel source followers in each column, the pixel output when the source potential of the read current source 50 fluctuates due to noise or the like can be obtained. Noise propagation is suppressed.

(Embodiment 3)
Hereinafter, the configuration and operation of the solid-state imaging device 3 according to Embodiment 3 of the present invention will be described with reference to the drawings. Hereinafter, only differences from the solid-state imaging device 1 according to Embodiment 1 will be described.

The solid-state imaging device 3 according to the present embodiment uses a multi-band constant voltage circuit 400 instead of the low-band constant voltage circuit and the high-band constant voltage circuit with respect to the solid-state imaging device 1 according to the first embodiment. It is different in point.

FIG. 10 is a block diagram showing a configuration of the solid-state imaging device 3 according to Embodiment 3 of the present invention. FIG. 11 is a block diagram showing a configuration of a multiband constant voltage circuit 400 included in the solid-state imaging device 3 according to Embodiment 3 of the present invention. In addition, the same code | symbol is attached | subjected about the element similar to FIG. The solid-state imaging device 3 has the same configuration as the solid-state imaging device 1 according to Embodiment 1 except for the multiband constant voltage circuit 400.

In the present embodiment, the multi-band constant voltage circuit 400 includes a high-band constant voltage output that is output without band limitation, a band-limiting resistor 102, and a band-limiting capacitor with respect to a single output of a general band gap reference circuit 105. The third constant voltage circuit includes a low-band constant voltage output that is band-limited by inserting a low-pass filter 103 by 101. That is, the multi-band constant voltage circuit 400 includes a low-band constant voltage circuit 100 that is a first constant voltage circuit and a high-band constant voltage circuit 200 that is a second constant voltage circuit. Part of the components and the components of the high-band constant voltage circuit 200 are shared, and the constant voltage from the low-band constant voltage circuit and the constant voltage from the high-band constant voltage circuit are output independently. In this embodiment, the band gap circuit is exemplified. However, as long as the voltage source circuit generates voltage, for example, a voltage generation circuit using resistance voltage division does not depart from the object and scope of the present invention. . Further, the number of voltage outputs is not limited, and there may be an arbitrary number of voltage outputs of two or more.

The high-band constant voltage output has a large amount of noise because the band is not limited, but the startup time as a constant-voltage circuit is fast. On the other hand, the low-band constant voltage output is band-limited, so the amount of noise is small and can be used as a low-noise circuit. Time is slow.

For the band limiting capacitor 101, it is preferable to use an external capacitor in order to greatly limit the band. However, it is not always necessary to use an external capacitor. The use of this capacity does not depart from the purpose and scope of the present invention. In this embodiment, an example in which the low-pass filter, which is the first filter circuit, is connected only to the low-band constant voltage output, but the second high-band constant voltage output is not affected by the start-up time. Even if a low-pass filter, which is a filter circuit, is connected, it does not depart from the object and scope of the present invention. In this case, the band of the low-pass filter connected to the low-band constant voltage output is set lower than the band of the low-pass filter connected to the high-band constant voltage output. In addition, it is not always necessary to perform band limitation using a low-pass filter, and band limitation by another band limiting unit may be used. In addition, a low-pass filter is not configured with a band-limiting resistor and a band-limiting capacitor, but even when only a capacitive element for band-limiting is connected, the circuit output impedance of the previous stage of the band-limiting capacitor is used as a resistor, Therefore, the same effect as in the present embodiment can be obtained, and a resistance element can be dispensed with.

Note that the multi-band constant voltage circuit 400 exemplified in this embodiment is an example, and if a constant voltage output of a plurality of bands is generated from a single constant voltage circuit, the detailed circuit is not limited.

As described above, the voltage conversion circuit 300 requires a startup time, and normal imaging cannot be performed until the voltage conversion circuit 300 is started. Therefore, the startup delay of the voltage conversion circuit 300 is the startup of the solid-state imaging device 3. It is necessary to limit to a range that does not affect the time constraint.

In the present embodiment, since the high-band constant voltage output of the multi-band constant voltage circuit 400 is used to supply the reference voltage to the voltage conversion circuit 300, the start-up delay of the constant voltage circuit itself is small, and the start-up of the voltage conversion circuit 300 is Compared with the case where a low-band voltage output is used, the speed is increased. As described above, since the startup of the voltage conversion circuit 300 is accelerated, it is possible to reduce the inrush current at the time of switching and to reduce the switching frequency, and to reduce the switching noise itself generated by the booster circuit. Noise can be reduced. As described above, the generated voltage of the voltage conversion circuit 300 is not a big problem even if a reference voltage and a reference current that are not band-limited are supplied, but noise mixed in the pixel source follower is not output to the pixel output. Propagation greatly affects the image quality.

In this embodiment, by using a low-band constant voltage output for supplying the reference voltage to the read current source 50, the amount of noise of the reference voltage is suppressed, and the noise of the pixel output is reduced. Further, due to the band limitation, the start-up delay of the constant voltage circuit itself is large, and the delay until the operation of the pixel source follower is large. In this respect, the start-up of the voltage conversion circuit 300 and the low-band constant-voltage output can be performed in parallel, and the start-up time such as several tens to several hundreds of ms that is the same as the start-up time of the voltage conversion circuit 300 Can be given to. Therefore, sufficient band limitation can be performed on the low-band constant voltage output, and noise can be greatly reduced without degrading the startup time as the solid-state imaging device 3.

As described above, the solid-state imaging device 3 according to the present embodiment includes the multi-band constant voltage circuit 400, and at least the high-band constant voltage that is the second voltage generated by the multi-band constant voltage circuit 400 is at least a voltage. Used in the conversion circuit 300. The solid-state imaging device 3 uses at least the read current source 50 with the low-band constant voltage that is the first voltage generated by the multi-band constant voltage circuit 400. As a result, it is possible to achieve both a start-up time as the solid-state imaging device 3 and a low noise and high dynamic range.

(Embodiment 4)
Hereinafter, the configuration and operation of the solid-state imaging device 4 according to Embodiment 4 of the present invention will be described with reference to the drawings. Hereinafter, only differences from the solid-state imaging device 1 according to Embodiment 1 will be described.

The solid-state imaging device 4 according to the present embodiment uses a multi-band constant current circuit 407 instead of the low-band constant current circuit and the high-band constant current circuit with respect to the solid-state imaging device 2 according to the second embodiment. It is different in that. Also, the gate input to the read current source 50 is not a reference voltage, the read current source 50 forms a mirror circuit, and the reference current becomes an input to the read current source 50.

FIG. 12 is a block diagram showing a configuration of the solid-state imaging device 4 according to Embodiment 4 of the present invention. FIG. 13 is a block diagram showing a configuration of a multiband constant current circuit 407 included in the solid-state imaging device 4 according to Embodiment 4 of the present invention. The same elements as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted here. The solid-state imaging device 4 has the same configuration as the solid-state imaging device 2 according to the second embodiment except for the multi-band constant current circuit 407.

In the present embodiment, the multi-band constant current circuit 407 is a VI conversion circuit that is a second voltage-current conversion circuit for a single output of a general bandgap reference circuit 105 that is a fourth constant voltage circuit. 500, a high-band constant current output in which the current obtained by 500 is output without band limitation, and a low-band constant current in which the current obtained by the VI conversion circuit 500, which is the first voltage-current conversion circuit, is band-limited by the band-limiting capacitor 101. And a third constant current circuit having an output. That is, the multi-band constant current circuit 407 includes a low-band constant current circuit 107 that is a first constant current circuit and a high-band constant current circuit 207 that is a second constant current circuit. The band gap reference circuit 105 which is a common component with the high-band constant current circuit 207 is shared, and the constant current from the low-band constant current circuit and the constant current from the high-band constant current circuit are output independently. Note that the connection method between the VI conversion circuit 500 and the band limiting capacitor 101 exemplified in this embodiment is an example, and the configuration of the VI conversion circuit 500 is not limited as long as the circuit has a VI conversion function. For example, a simple source grounding circuit may be used. Further, if the band of the output current of the VI conversion circuit 500 is limited, the band limiting method of the VI conversion circuit is not limited. For example, the filter circuit may be configured or connected in the VI conversion circuit instead of the connection of the band limiting capacitor. Further, the number of current outputs is not limited, and there may be an arbitrary number of current outputs of two or more.

The high-band constant current output has a large amount of noise because the band is not limited, but the startup time as a constant-current circuit is fast. On the other hand, the low-band constant current output is band-limited, so the amount of noise is small and can be used as a low-noise circuit. However, due to the charging delay of the band-limiting capacitor 101, the startup time as a constant-current circuit is Slow.

For the band limiting capacitor 101, it is preferable to use an external capacitor in order to greatly limit the band. However, it is not always necessary to use an external capacitor. The use of this capacity does not depart from the purpose and scope of the present invention. In this embodiment, the band gap circuit is exemplified. However, as long as the voltage source circuit generates voltage, for example, a voltage generation circuit using resistance voltage division does not depart from the object and scope of the present invention. . In the present embodiment, the example in which the band limiting capacitor, which is the third capacitor element, is connected only to the VI conversion circuit that outputs the low-band constant current output. However, the high-band constant current is not affected by the start-up time. Even if a band limiting capacitor, which is the fourth capacitor element, is connected to the VI conversion circuit that outputs the output, it does not depart from the object and scope of the present invention. In this case, the band limiting capacity connected to the VI conversion circuit that outputs the low-band constant current output is set to be larger than the band limiting capacity connected to the VI conversion circuit that outputs the high-band constant current output. Become. Even if the band is limited by configuring or connecting the filter circuit in the VI conversion circuit, not only the third filter circuit is connected to the VI conversion circuit that outputs a low-band constant current output, but also the startup. A fourth filter circuit may be connected to a VI conversion circuit that outputs a high-band constant current output within a range that does not affect time. Also in this case, the low-band constant current output band is set lower than the high-band constant current output band.

As described above, the voltage conversion circuit 300 requires a start-up time, and normal imaging cannot be performed until the voltage conversion circuit 300 is started. Therefore, the start-up delay of the voltage conversion circuit 300 is the start-up of the solid-state imaging device 4. It is necessary to limit to a range that does not affect the time constraint.

In this embodiment, since the high-band constant current output of the multi-band constant current circuit 407 is used to supply the reference current to the voltage conversion circuit 300, the start-up delay of the constant current circuit itself is small, and the start-up of the voltage conversion circuit 300 is Compared with the case where a low-band constant current output is used, the speed is increased. As described above, since the startup of the voltage conversion circuit 300 is accelerated, it is possible to reduce the inrush current at the time of switching and to reduce the switching frequency, and to reduce the switching noise itself generated by the booster circuit. Noise can be reduced. As described above, the generated voltage of the voltage conversion circuit 300 is not a big problem even if a reference voltage and a reference current that are not band-limited are supplied, but noise mixed in the pixel source follower is not output to the pixel output. Propagation greatly affects the image quality.

In this embodiment, by using a low-band constant current output for supplying the reference current to the read current source 50, the amount of noise of the reference current is suppressed, and the noise of the pixel output is reduced. In addition, due to the band limitation, the startup delay of the constant current circuit itself is large, and the delay until the operation of the pixel source follower is large. In this respect, the startup of the voltage conversion circuit 300 and the low-band constant current output can be operated in parallel. Can be given. Therefore, sufficient band limitation can be performed on the low-band constant current output, and noise can be greatly reduced without degrading the startup time as the solid-state imaging device 4.

As described above, the solid-state imaging device 4 according to the present embodiment includes the multi-band constant current circuit 407, and at least the high-band constant current that is the second current generated by the multi-band constant current circuit 407 is at least a voltage. Used in the conversion circuit 300. Further, the solid-state imaging device 4 uses the low-band constant current that is the first current generated by the multi-band constant voltage circuit 400 for at least the read current source 50. As a result, it is possible to achieve both a start-up time as the solid-state imaging device 4 and a reduction in noise and a high dynamic range.

Although the first to fourth embodiments have been described above, the solid-state imaging device according to the present invention is not limited to the above-described embodiments. Other embodiments realized by combining arbitrary constituent elements in the first to fourth embodiments, and various modifications conceivable by those skilled in the art without departing from the gist of the present invention to the first to fourth embodiments. Modifications obtained in this way and various devices incorporating the solid-state imaging device according to the present invention are also included in the present invention.

In the solid-state imaging devices 1 to 4 according to the embodiments of the present invention, each unit pixel 5 has a structure having one photodiode, a transfer transistor, a floating diffusion, a reset transistor, and an amplification transistor, so-called one-pixel one-cell structure. Have taken. However, the solid-state imaging device of the present invention includes a plurality of photodiodes in addition to the one-pixel / one-cell structure, and further shares any one or all of the floating diffusion, the reset transistor, and the amplification transistor in the unit cell. A structure, a so-called multi-pixel 1-cell structure can be used.

The solid-state imaging devices 1 to 4 of the present invention may have a structure in which the photodiode is formed on the surface of the semiconductor substrate, that is, on the same side as the surface on which the gate terminal and the wiring of the transistor are formed. Use a so-called back-illuminated image sensor (back-illuminated solid-state imaging device) structure in which the photodiode is formed on the back surface side of the semiconductor substrate, that is, the surface on which the gate terminal and wiring of the transistor are formed. You can also.

The solid-state imaging device according to the present invention is useful as a digital still camera, a digital video camera, and the like that require high image quality such as high-speed startup, low noise, and high dynamic range.

1, 2, 3, 4, 1000 Solid-

state imaging device

5, 1003

Unit pixel

10, 1010

Pixel array

30, 1030

Photodiode

31, 1031

Transfer transistor

32, 1032

Reset transistor

33, 1033

Select transistor

34, 1034 Read transistor 40 Vertical scan Circuit 41, 1041 Transfer

transistor control line

42, 1042 Reset

transistor control line

43, 1043 Selection transistor control line 44

Decoder

45, 1045 Vertical signal line 47

Vertical driver

50, 1050 Read

current source

55, 1062 Horizontal signal line 56 Column ADC
57 Reference signal generation unit 60 Horizontal scanning circuit 61, 1061 Horizontal selection transistor 65 Horizontal control line 67 Output circuit 70 Timing control unit 100 Low-band

constant voltage circuit

101, 705, 706 Band-limiting capacitor 102 Band-limiting resistor 103 Low-pass filter 105 Band gap Reference circuit 107 Low-band constant current circuit 200 High-band constant voltage circuit 207 High-band constant current circuit 300 Voltage conversion circuit 301 Comparison circuit 400 Multi-band constant voltage circuit 407 Multi-band constant current circuit 415 Voltage comparison unit 416 Count unit 418 Memory unit 500

VI conversion circuit

701, 702 Voltage dividing circuit 1040 Vertical scanning unit 1060 Horizontal scanning unit 1069 Amplifier 1080 AD conversion unit 1090 Signal processing unit 1100 Booster circuit

Claims

A plurality of pixels arranged in a matrix and converting light into a signal voltage;
A vertical signal line provided for each pixel column;
A current source circuit that is provided for each pixel column and supplies a current for reading the signal voltage to the vertical signal line by supplying a first voltage;
A voltage conversion circuit that generates a voltage different from the power supply voltage by being supplied with the second voltage;
A vertical scanning circuit that drives the plurality of pixels in a row sequence using the voltage generated by the voltage conversion circuit, and reads the signal voltage from the pixels in the corresponding row via the vertical signal line and the current source circuit; ,
A first constant voltage circuit for supplying the first voltage from which a high frequency component is removed from the second voltage to the current source circuit;
A solid-state imaging device comprising: a second constant voltage circuit that supplies the second voltage to the voltage conversion circuit.
further,
A first capacitive element connected to the first constant voltage circuit;
The solid-state imaging device according to claim 1, further comprising a second capacitor element connected to the second constant voltage circuit and having a capacitance value different from that of the first capacitor element.
further,
A first filter circuit connected to the first constant voltage circuit;
The solid-state imaging device according to claim 1, further comprising: a second filter circuit connected to the second constant voltage circuit and having a higher passband than the first filter circuit.
A capacitor element is connected to one of the first constant voltage circuit and the second constant voltage circuit,
The solid-state imaging device according to claim 1, wherein a capacitive element is not connected to the other of the first constant voltage circuit and the second constant voltage circuit.
A filter circuit is connected to the first constant voltage circuit,
The solid-state imaging device according to claim 1, wherein a filter circuit is not connected to the second constant voltage circuit.
The first constant voltage circuit and the second constant voltage circuit are included in a third constant voltage circuit,
The third constant voltage circuit partially shares components of the first constant voltage circuit and components of the second constant voltage circuit, and the first voltage from the first constant voltage circuit. 6. The solid-state imaging device according to claim 1, wherein the first voltage and the second voltage from the second constant voltage circuit are independently output.
A plurality of pixels arranged in a matrix and converting light into a signal voltage;
A plurality of vertical signal lines provided for each pixel column;
A current source circuit that is provided for each pixel column and supplies a current for reading the signal voltage to the vertical signal line by supplying a first current;
A voltage conversion circuit that generates a voltage different from the power supply voltage by supplying the second current;
A vertical scanning circuit that drives the plurality of pixels in a row sequence using the voltage generated by the voltage conversion circuit, and reads the signal voltage from the pixels in the corresponding row via the vertical signal line and the current source circuit; ,
A first constant current circuit for supplying the current source circuit with the first current from which a higher frequency component is removed than the second current;
A solid-state imaging device comprising: a second constant current circuit that supplies the second current to the voltage conversion circuit.
further,
A first capacitive element connected to the first constant current circuit;
The solid-state imaging device according to claim 7, further comprising a second capacitor element connected to the second constant current circuit and having a capacitance value different from that of the first capacitor element.
further,
A first filter circuit connected to the first constant current circuit;
The solid-state imaging device according to claim 7, further comprising: a second filter circuit connected to the second constant current circuit and having a higher pass band than the first filter circuit.
A capacitor element is connected to one of the first constant current circuit and the second constant current circuit,
The solid-state imaging device according to claim 7, wherein a capacitive element is not connected to the other of the first constant current circuit and the second constant current circuit.
A filter circuit is connected to the first constant current circuit,
The solid-state imaging device according to claim 7, wherein a filter circuit is not connected to the second constant current circuit.
12. The solid-state imaging according to claim 7, wherein at least one of the first constant current circuit and the second constant current circuit is a constant current circuit that generates a current by dividing a voltage. apparatus.
The first constant current circuit includes a fourth constant voltage circuit and a first voltage / current conversion circuit,
The second constant current circuit includes the fourth constant voltage circuit and a second voltage / current conversion circuit,
The first constant current circuit and the second constant current circuit are included in a third constant current circuit,
In the third constant current circuit, the first constant current circuit and the second constant voltage circuit share the fourth constant voltage circuit, and the first constant current circuit outputs the first constant current circuit. The solid-state imaging device according to claim 7, wherein a current and the second current from the second constant current circuit are independently output.
further,
A third capacitive element connected to the first voltage-current conversion circuit;
The solid-state imaging device according to claim 13, further comprising: a fourth capacitor element connected to the second voltage-current conversion circuit and having a capacitance value different from that of the third capacitor element.
further,
A third filter circuit connected to the first voltage-current converter circuit;
The solid-state imaging device according to claim 13, further comprising: a fourth filter circuit connected to the second voltage-current conversion circuit and having a higher passband than the third filter circuit.
One of the first voltage-current conversion circuit and the second voltage-current conversion circuit is connected to a capacitive element,
The solid-state imaging device according to claim 13, wherein a capacitive element is not connected to the other of the first voltage-current conversion circuit and the second voltage-current conversion circuit.
A filter circuit is connected to the first voltage-current conversion circuit,
The solid-state imaging device according to claim 13, wherein a filter circuit is not connected to the second voltage-current conversion circuit.