TWI413882B - Reference current generating apparatus and method - Google Patents

Abstract

Reference current generating apparatus and method. The reference current generating apparatus includes a current generating circuit, a compensating current generating unit, and a control signal generating unit. The current generating circuit, coupled to an external resistance, generates a reference current according to a reference voltage. The compensating current generating unit, coupled to the current generating circuit, includes at least a current branch to provide a compensating current and outputs the compensating current according a control signal selectively to the current generating circuit for generating the reference current. The control signal generating unit, coupled to the current generating circuit and compensating current generating unit, generates the control signal according to a detection voltage corresponding to resistance value of the external resistance, wherein the control signal indicates one of a plurality of states and each of the states corresponds to a resistance value of the external resistance. The control signal can be further utilize to set another circuit unit.

Description

Reference current generating device and method

The present invention relates to a reference current generating device and method thereof, and more particularly to a reference current generating device capable of generating a control signal and a method thereof.

The bandgap reference circuit is widely used in integrated circuits to provide a stable reference voltage. This reference voltage is more accurate than the voltage of the external power supply, and it is less affected by temperature variations and variations in power supply. The bandgap reference circuit utilizes a circuit proportional to the absolute temperature to compensate for the negative temperature coefficient of the bipolar transistor base emitter, thereby providing a reference voltage that is substantially immune to temperature variations.

As shown in FIG. 1, a conventional reference current generating device 10 includes a bandgap reference circuit 100 and a current generating circuit 110. The bandgap reference circuit 100 includes an operational amplifier, a PMOS transistor, a BJT transistor, and a resistor. With the principle of the above-described band gap reference circuit, the reference current generating device 10 generates the reference voltage VBG which is substantially unaffected by the temperature change. The current generating circuit 110 is connected to the current generating circuit 110 to generate a corresponding current Iext, and finally the reference current Iref is generated. The reference current Iref is a reference current source that is insensitive to the process, voltage and temperature. When the design of the current generating circuit is completed, for example, the number of transistors of the content is fixed, a fixed reference current value is obtained, and the resistor Rext must also be obtained. Fixed at a certain resistance. Generally, in the design of the wafer, the resistor Rext is placed outside the wafer including the reference current generating device 10 to become the external resistor Rext; when the circuit designer uses the wafer, a fixed resistor must be externally connected according to the specification of the wafer. The external resistor Rext of the value allows the wafer to function properly according to its specifications.

The present invention relates to a reference current generating device and method thereof. The reference current generating device is connected to a preset external resistor of different resistance values to generate a desired reference current, for example, generating a reference current of the same magnitude, and generating different control signals corresponding to different external resistor values.

According to a first aspect of the invention, a reference current generating device is provided. The reference current generating device includes a current generating circuit, a compensation current generating unit, and a control signal generating unit. The current generating circuit is coupled to an external resistor for generating a reference current according to a reference voltage. The compensation current generating unit is coupled to the current generating circuit and includes at least one current branch to provide a compensation current. The compensation current generating unit selectively outputs a compensation current to the current generating circuit according to a control signal to generate a reference current. The control signal generating unit is coupled to the current generating circuit and the compensation current generating unit, and generates a control signal according to the detection voltage corresponding to one of the resistance values of the external resistor, wherein the control signal represents one of a plurality of states, and each state corresponds to an external resistor. A resistance value.

According to a second aspect of the present invention, a reference current generating method is proposed. This method includes the following steps. A current generating circuit is provided to generate a reference current according to a reference voltage and an external resistor. A control signal is generated according to the detection voltage corresponding to one of the resistance values of the external resistor, wherein the control signal represents one of a plurality of states, and each state corresponds to a resistance value of the external resistor. A compensation current is selectively provided in accordance with the control signal to cause a current generating circuit to generate a reference current.

In order to better understand the above and other aspects of the present invention, the preferred embodiments are described below, and in conjunction with the drawings, the detailed description is as follows:

An embodiment of a reference current generating device and method thereof is presented below. In an embodiment, the reference current generating device is connected to the preset external resistors of different resistance values to generate the same size of the reference current, and can generate different control signals corresponding to the external resistors. Furthermore, the reference current generating device can use different control signals to change the setting of other circuits by using different external resistance values, and can bring various new uses to improve the convenience of setting the circuit. Reduce the complexity of the overall circuit design.

FIG. 2A is a circuit block diagram of a reference current generating device according to an embodiment. The reference current generating device 20 includes a current generating circuit 210, a compensation current generating unit 220, and a control signal generating unit 230. The current generating circuit 210 is coupled to an external resistor Rext for generating a reference current Iref according to a reference voltage VBG. The reference voltage VBG is generated, for example, by a bandgap reference circuit 200, or as a chip or system internal to the reference current generating device 20. The compensation current generating unit 220 is coupled to the current generating circuit 210 and includes one or more current branches to provide a compensation current Icp. The compensation current generating unit 220 selectively supplies the compensation current Icp according to a control signal OPT. The current generating circuit 210 is applied to generate a reference current Iref. The control signal generating unit 230 is coupled to the current generating circuit 210 and the compensation current generating unit 230 to detect the voltage generating control signal OPT according to one of the resistance values of the external resistor Rext to control the compensation current generating unit 230 to selectively provide compensation. The current Icp is supplied to the current generating circuit 210 to generate a reference current Iref. Further, the external resistor Rext can be implemented as being included in the reference current generating device 20 or outside the wafer or system including the reference current generating device 20.

According to the reference current generating device 20 in FIG. 2A, the resistance values of the plurality of external resistors Rext can be designed to cause the control signal generating unit 230 to generate different control signals OPT correspondingly to control the compensation current generating unit 220 to provide an appropriate size. Compensation current Icp. After the current generating circuit 210 obtains the compensation current Icp, in combination with the current generated therein, the desired reference current Iref can be generated. The control signal OPT in Figure 2A may represent one or more control signals, such as digital signals or logic levels.

Please refer to FIG. 2B, which illustrates that different control signals generated by the reference current generating device 20 can be used as settings for changing other circuits. The circuit unit 1 includes the above-described reference current generating device 20, and the external resistor Rext is designed to be suitable for two resistance values, such as 100 Ω or 200 Ω, and the corresponding control signal OPT represents logic 0 or 1. As such, the circuit unit 2 can be designed to perform different processing or enter a certain mode of operation in response to the control signal OPT. Thus, the circuit unit 2 can be set without using a firmware or other software or changing the circuit design.

The following is a practical example. When the electronic components are customized by using the circuit units 1 and 2 in FIG. 2B, it is assumed that the circuit unit 2 is a multimedia chip. For the A customer's product, the control signal OPT represents logic 0 as described above. In order to automatically enter the low-energy general operation mode required by the A customer when starting up. For the B customer's products, the demand is high performance, so that the control signal OPT stands for logic 1, so that when it is turned on, it automatically enters the high-performance operation mode required by the A customer. Thus, it can be explained that the reference current generating device 20 can bring a variety of new uses to improve the convenience of setting the circuit and to reduce the complexity of the overall circuit.

The various embodiments are described below by way of example with reference to current generating device 20.

FIG. 3A is an example of a reference current generating device 30 according to the embodiment of FIG. 2A, wherein the external resistor Rext may be one of two pre-designed resistance values, correspondingly generating a control signal indicating two different states. The transistors X3 and Xn shown in the figure 3A, for example, the symbols Xm and Xn shown next to the transistors m1 and m2, respectively, indicate that the transistor m1 can be substantially the same as the aspect ratio (W/L) of m crystal structures. A transistor (such as a PMOS or an NMOS) is implemented in parallel, and the transistor m2 can be implemented in a manner equivalent to n such transistors, in which m and n are both positive integers.

The reference current generating device 30 includes a current generating circuit 310, a compensation current generating unit 320, and a control signal generating unit 330. For example, the current generating circuit 310 can be implemented as a current mirror or other current generating circuit, such as a feedback current mirror shown in FIG. 3A, including an operational amplifier OP, transistors m1 and m2. The compensation current generating unit 320 includes at least one current branch, for example, a current branch composed of the transistor m3 and the switch sw for selectively providing a compensation current Icp to the current according to a control signal OPT. Circuit 310 is generated to generate a reference current Iref. The control signal generating unit 330 generates the control signal OPT according to the detection voltage VT corresponding to one of the resistance values of the external resistor Rext, to control the compensation current generating unit 330 to selectively supply the compensation current Icp to the current generating circuit 310 to generate the reference current Iref. The control signal generating unit 330 includes, for example, a voltage dividing circuit composed of a transistor m4 and a resistor R1 to generate a detection voltage VT, and includes a comparator comp to compare the detection voltage VT and a threshold value (such as a reference voltage VBG). A control signal OPT is generated. In this example, the reference voltage VBG is not limited to the gate threshold. Other examples are obtained by dividing the power supply VDD or by other power sources. Regardless of the design, the comparison result can be combined with the demand to generate the corresponding control signal OPT. .

The resistance of the external resistor Rext is two different resistance values Rx and k1*Rx, respectively, where k1>0. As shown in FIG. 2A, when the external resistor Rext=Rx is used, the current magnitude Iext flowing through the external resistor Rext is VBG/Rx. The control signal generating unit 330 obtains the detection voltage VT of VBG*R1/Rx*(n/m). In this example, by designing the resistance of the resistor R1, the detection voltage VT will be greater than the gate threshold (such as the reference voltage VBG), so the comparator comp outputs the control signal OPT (if it is low or regarded as logic 0) to represent that no compensation is required. Current. The switch sw of the current branch of one of the compensation current generating unit 320 is controlled by the control signal OPT. At this time, the control signal OPT is 0, and the switch sw is open, so the compensation current Icp corresponding to the switch sw is not supplied to the current generating circuit. 310, or can be regarded as the provided compensation current Icp at this time is 0. In this case, the reference current Iref is VBG/Rx*(n/m).

As shown in FIG. 3B, when the external resistor Rext is k1 times Rx, the current magnitude Iext flowing through the external resistor Rext is VBG/(k1*Rx). The detection voltage VT obtained by the control signal generating unit 330 is VBG*R1/(k1*Rx)*(n/m). At this time, the detection voltage VT is less than the threshold value (such as the reference voltage VBG), and the comparator comp outputs the control signal OPT as high or as a logic 1 to represent the required compensation current. Since the control signal OPT is 1, the switch sw is closed, so the compensation current Icp corresponding to the switch sw is supplied to the current generating circuit 310. Since the transistor m3 represents (k1-1)n parallel structures of the above-described transistors having the same aspect ratio. Therefore, in this case, the reference current Iref is still VBG/Rx*(n/m).

As can be seen from the above, for an arbitrarily selected Rx or k1 times Rx as an external resistance value, the reference current generating device 30 can generate a stable current source VBG/Rx*(n/m), and generate control in response to different resistance values. The signal OPT has different potentials, and the control signal OPT can be used to control circuits of other functions, as shown in FIG. 2B.

In other embodiments, the reference current generating device 40 as shown in FIG. 4 further expands the application of the above example, and three different external resistor values, such as Rx, k1*Rx, and k2*Rx, can be used to generate control. The signal is represented by three different states, such as two-bit digital signals 00, 10, and 11.

Referring to FIG. 4, the reference current generating device 40 includes a current generating circuit 410, a compensation current generating unit 420, and a control signal generating unit 430. For example, current generation circuit 410 can be implemented as current generation circuit 310.

Different from FIG. 3A, the compensation current generating unit 420 includes at least two current branches, for example, a current branch composed of the transistor m3 and the switch sw1, and another composed of the transistor m4 and the switch sw2. A current branch. The compensation current generating unit 420 selectively supplies a compensation current Icp to the current generating circuit 410 to generate a reference current Iref according to the control signals OPT1 and OPT2 (which can be regarded as sub-signals of the control signal OPT).

In addition, the control signal generating unit 430 generates the control signals OPT1 and OPT2 according to the detection voltage VT corresponding to one of the resistance values of the external resistor Rext, to control the compensation current generating unit 430 to selectively provide the compensation current Icp to the current generating circuit 410 to generate Reference current Iref. The control signal generating unit 430 includes, for example, a transistor m5 and a resistor R1 to generate a detection voltage VT. The control signal generating unit 430 further includes two comparators, a first comparator comp1 and a second comparator comp2, for respectively comparing the detection voltage VT and a first threshold value (such as voltage VREF) to generate the control signal OPT1, and comparing and detecting The voltage VT and a second threshold (eg, voltage VBG2) are used to generate the control signal OPT2. In Fig. 4, a comparison voltage generation circuit 440 is used to generate the first threshold value (e.g., voltage VREF) and the second threshold (e.g., voltage VBG2). The comparison voltage generating circuit 440 generates two gate threshold values by using the operational amplifier OP2 and the transistor m6 through the resistors R2 and R3 in accordance with the power supply voltage VDD and the reference voltage VBG. The comparison voltage generating circuit 440 is not limited to the above-described architecture, nor is it limited to use the reference voltage VBG as a reference source for the gate threshold. Therefore, no matter what kind of design, the comparison result can generate the corresponding control signals OPT1 and OPT2 according to the requirements.

The reference current generating device 40 of FIG. 4 can use three different external resistance values, such as Rx, k1*Rx, and k2*Rx. When the resistance value of the external resistor Rext is Rx, the current magnitude Iext flowing through the external resistor Rext is VBG/Rx. The control signal generating unit 430 obtains the detected voltage VT as VBG*R1/Rx*(n/m). In this example, by designing the resistance values of the resistors R1, R2, and R3, the detection voltage VT is greater than the first threshold (eg, the voltage VREF, which is equivalent to the reference voltage VBG), such that the first comparator comp1 and the second comparator comp2 The output control signals OPT1 and OPT2 are respectively low or regarded as logic 0. The switches sw1 and sw2 on the current branch of the compensation current generating unit 420 flowing through the transistors m3 and m4' are controlled by the control signals OPT1 and OPT2. At this time, the switches sw1 and sw2 are open circuits, so the compensation current Icp is not supplied to the current generation. The circuit 410, or can be regarded as the provided compensation current Icp, has a value of zero at this time. In this case, the reference current Iref is VBG/Rx*(n/m).

When the external resistor Rext is k1 times Rx, the current magnitude Iext flowing through the external resistor Rext is VBG/(k1*Rx). The detection voltage VT obtained by the control signal generating unit 430 is VBG*R1/(k1*Rx)*(n/m). At this time, the detection voltage VT is greater than the second threshold (such as the voltage VBG2) and less than the first threshold (such as the voltage VREF), such that the first comparator comp1 outputs the control signal OPT1 as high or as logic 1, the second comparison The comp2 output control signal OPT2 is low. Therefore, the switch sw1 is closed, and the switch sw2 is open, so the current flowing through the transistor m3 passes through the switch sw1 to become the compensation current Icp to be supplied to the current generating circuit 410. Therefore, in this case, the reference current Iref is still VBG/Rx*(n/m).

When the external resistor Rext is k2 times Rx, the current magnitude Iext flowing through the external resistor Rext is VBG/(k2*Rx). The detection voltage VT obtained by the control signal generating unit 430 is VBG*R1/(k2*Rx)*(n/m). At this time, the detection voltage VT is smaller than the second threshold (such as the voltage VBG2), so that the first comparator comp1 and the second comparator comp2 output the control signal OPT1 and the control signal OPT2 are both high. Therefore, the switches sw1 and sw2 are both closed, so that the currents flowing through the transistors m3 and m4' pass through the switches sw1 and sw2 to become the compensation current Icp to be supplied to the current generating circuit 410. Since the transistor m4 represents (k2-k1)n parallel structures of the above-described transistors having the same aspect ratio. Therefore, in this case, the reference current Iref is still VBG/Rx*(n/m).

As can be seen from the example of FIG. 4 above, the control signals OPT1 and OPT2 can have different outputs according to the selection of external resistors of different resistance values, and can be used as a two-element control signal.

Furthermore, the first and second threshold values used in FIG. 4 are generated in addition to the comparison voltage generating circuit 440 described above, and in other examples, may be considered as internal or external to the system or wafer in which the reference current generating device 40 is located. Provided. Therefore, the reference current generating device 40 does not have to include the comparison voltage generating circuit 440. It can be seen that the implementation manner of the compensation current generating unit 420 and the control signal generating unit 430 is not limited to the above embodiment, and the comparison result of the control signal generating unit 430 can be matched with the multiple resistance values of the external resistor Rext. The various embodiments of the control signals OPT1 and OPT2, and the current branch in the control signal generating unit 430, which can provide the compensation current Icp, can be considered as embodiments covered by the present invention.

In addition, each of the above embodiments is described by taking an example in which different external resistance values can correspond to substantially the same reference current Iref. However, the implementation of the reference current generating device is not limited thereto. In other embodiments, different reference currents Iref may be designed to correspond to different external resistors according to actual application requirements. In implementation, various embodiments in which the reference current generating device can generate corresponding control signals for different external resistance values can be considered as embodiments covered by the present findings.

Furthermore, the transistor in the above embodiment, such as the transistor m1 of FIG. 2A or FIG. 4, may be implemented in parallel, in addition to m of the above-mentioned transistors having the same aspect ratio, other numbers may be used. However, the length of the transistor is different from that of other transistors in parallel or in series. In still other embodiments, the transistors m1 and m2 can be implemented using only two transistors having a width to length ratio of m:n, where m and n can take values of fractional or integer. Embodiments of other transistors may also be implemented in various ways as described above.

Further, according to the above embodiment, the present invention also proposes a reference current generating method including the following steps. A current generating circuit is provided to generate a reference current according to a reference voltage and an external resistor. A control signal is generated according to the detection voltage corresponding to one of the resistance values of the external resistor, wherein the control signal represents one of a plurality of states, and each state corresponds to a resistance value of the external resistor. A compensation current is selectively provided in accordance with the control signal to cause a current generating circuit to generate a reference current. The above steps can be implemented in accordance with various embodiments of Figures 2A through 4. In addition, as shown in FIG. 2B, the control signals generated by this method can be used to set other circuit units.

The reference current generating device and method disclosed in the above embodiments can elastically connect external resistors of different resistance values to generate a reference current of a desired magnitude, for example, generate a reference current of the same magnitude, and generate different control signals. Furthermore, the reference current generating device can use different control signals to change the setting of other circuits by using different external resistance values, and can bring various new uses to improve the convenience of setting the circuit. Reduce the complexity of the overall circuit design.

In conclusion, the present invention has been disclosed in the above preferred embodiments, and is not intended to limit the present invention. A person skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

10. . . Conventional reference current generating device

20, 30, 40. . . Reference current generating device

100, 200. . . Bandgap reference circuit

110, 210, 310, 410. . . Current generating circuit

220, 320, 420. . . Compensation current generating unit

230, 330, 430. . . Control signal generating unit

440. . . Comparison voltage generating circuit

Comp, comp1, comp2. . . Comparators

OP, OP1, OP2. . . Operational Amplifier

M1, m2, m3, m4, m4', m5. . . Transistor

Sw, sw1, sw2. . . switch

R1, R2, R3. . . resistance

VBG. . . Reference voltage

Iref. . . Reference current

Icp. . . Compensation current

OPT, OPT1, OPT2. . . Control signal

Rext. . . External resistor

Figure 1 is a conventional reference current generating device.

FIG. 2A is a circuit block diagram of a reference current generating device according to an embodiment.

Figure 2B shows that the different control signals generated by the reference current generating means can be used to change the settings of other circuits.

3A and 3B are circuit block diagrams showing an example of a reference current generating device according to the embodiment of Fig. 2A.

Figure 4 is another example of a reference current generating device that can use three different external resistor values.

20. . . Reference current generating device

200. . . Bandgap reference circuit

210. . . Current generating circuit

220. . . Compensation current generating unit

230. . . Control signal generating unit

VBG. . . Reference voltage

Iref. . . Reference current

Icp. . . Compensation current

OPT. . . Control signal

Rext. . . External resistor

Claims (10)

A reference current generating device includes: a current generating circuit coupled to an external resistor for generating a reference current according to a reference voltage; a compensation current generating unit coupled to the current generating circuit, including at least one current branch a current branch for providing a compensation current, the compensation current generating unit selectively outputting the compensation current to the current generating circuit according to a control signal to generate the reference current; and a control signal generating unit coupled to the current generating The circuit and the compensation current generating unit generate the control signal according to a detection voltage corresponding to one of the resistance values of the external resistor, wherein the control signal represents one of a plurality of states, each of the states corresponding to a resistance of the external resistor . The reference current generating device of claim 1, wherein the current generating circuit comprises a current mirror coupled to the external resistor for generating the reference current according to the reference voltage. The reference current generating device of claim 1, wherein the compensation current generating unit comprises a plurality of current branches and at least one switching element, wherein the current branches are coupled in parallel through the at least one switching element to provide the Compensating current, wherein the at least one switching element is controlled by the control signal. The reference current generating device of claim 3, wherein the current generating circuit comprises a current mirror, and each of the current branches corresponds to a current branch of the current mirror. The reference current generating device of claim 4, wherein each of the current branches comprises a transistor. The reference current generating device of claim 1, wherein the control signal generating unit comprises: a voltage dividing circuit coupled to the current generating circuit for obtaining a magnitude corresponding to the resistance of the external resistor Detecting a voltage; and a comparison circuit responsive to the detected voltage and the at least one threshold to generate the control signal. The reference current generating device of claim 1, wherein the control signal generating unit compares the detected voltage and the at least one threshold to generate the control signal to control the compensation current generating unit to selectively control the control signal according to the control The signal outputs the compensation current to the current generating circuit to generate the reference current such that the reference current is substantially maintained at a current value. The reference current generating device of claim 1, wherein when the external resistor is a first resistance, the control signal represents a first state of the states, and the reference current is a current value; When the external resistor is a second resistance value, the control signal represents a second state of the states, and the compensation current generated by the compensation current generating unit corresponds to the second resistance value, and the compensation current is provided The current generating circuit is coupled to generate the reference current such that the reference current is substantially maintained at the current value. A reference current generating method includes: providing a current generating circuit to generate a reference current according to a reference voltage and an external resistor; generating a control signal according to the detected voltage corresponding to the resistance of the external resistor, wherein the control signal represents One of a plurality of states, each of the states corresponding to a resistance of the external resistor; and selectively outputting the compensation current to the current generating circuit to generate the reference current according to the control signal. The reference current generating method according to claim 9, wherein the control signal generating step generates the control signal by comparing the detected voltage and the at least one threshold, and the reference current is substantially maintained at a current value.