JP3773089B2 - Constant voltage generation circuit, nonvolatile memory, and semiconductor integrated circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a constant voltage generation circuit, and further to a constant voltage generation circuit capable of generating a constant voltage regardless of temperature change, power supply fluctuation, and manufacturing variation, for example, a write voltage in an electrically writable nonvolatile semiconductor memory, The present invention relates to a technique that is effective when used in a constant voltage generating circuit for generating an erasing voltage.
[0002]
[Prior art]
In recent years, a microcomputer having a nonvolatile memory as a built-in memory has been provided. Since the nonvolatile memory retains the stored contents even when the power is shut off, the microcomputer incorporating the nonvolatile memory is extremely effective for a mobile phone or the like that requires low power consumption.
[0003]
Non-volatile memory requires a higher voltage or negative voltage than the normal LSI power supply voltage for writing and erasing, so an internal power supply consisting of a booster circuit such as a charge pump circuit and a constant voltage generation circuit inside the chip. Often has a circuit.
[0004]
On the other hand, a nonvolatile memory stores information by applying a write voltage or an erase voltage to a storage element such as a MOSFET having a floating gate and changing its threshold value. In addition, since it is necessary to accurately change the threshold value of the memory element so that it falls within a predetermined voltage range, the write operation in the nonvolatile memory is considerably more than that in the volatile memory such as SRAM and DRAM. A long millisecond order time (for example, 10 mS) was used.
[0005]
[Problems to be solved by the invention]
Therefore, shortening the writing and erasing time in the nonvolatile memory is extremely important for increasing the speed and improving the throughput of a system such as a microcomputer or IC card in which the nonvolatile memory is incorporated. Furthermore, in order to shorten the writing and erasing time in the nonvolatile memory, it is important to improve the accuracy of the writing voltage and erasing voltage, and a constant voltage that generates a constant voltage regardless of manufacturing variations, temperature changes, and power supply fluctuations. A generator circuit is desired.
[0006]
FIG. 11 shows an example of a constant voltage generation circuit studied by the present inventors. The constant voltage generating circuit shown in FIG. 1 includes two Zener diodes Dz1 and Dz2 connected in series, a current control MOS transistor Qcr, and a voltage supply circuit that generates a gate voltage of the current control MOS transistor. The zener diodes Dz1 and Dz2 are connected to the output terminal of the booster circuit 10 such as a pump, and the negative voltage generated from the booster circuit is clamped by the reverse voltage of the zener diodes Dz1 and Dz2.
[0007]
The constant voltage generation circuit limits the current drawn from the zener diodes Dz1 and Dz2 by the booster circuit 10 by the MOS transistor Qcr and controls the control signals C1 to C5 applied to the voltage supply circuit, thereby controlling the voltage supply circuit. The level of the output voltage Vout can be adjusted by changing the output voltage, that is, the gate bias voltage of the transistor Qcr.
[0008]
However, in the constant voltage generation circuit of the above type, the current flowing through the Zener diodes Dz1 and Dz2 changes due to a temperature change or a power supply voltage change, and the output voltage changes. It has been clarified that there is a problem that it is difficult to set the output voltage value accurately because the characteristics of the circuit elements constituting the supply circuit change separately.
[0009]
An object of the present invention is to provide a constant voltage generating circuit capable of generating a constant voltage regardless of a temperature change.
[0010]
Another object of the present invention is to provide a constant voltage generating circuit capable of generating a constant voltage regardless of power supply fluctuations.
[0011]
Still another object of the present invention is to provide a constant voltage generating circuit capable of generating a constant voltage regardless of manufacturing variations.
[0012]
An object of the present invention is to provide a nonvolatile memory capable of shortening the write / erase time.
[0013]
SUMMARY OF THE INVENTION An object of the present invention is to provide a technique capable of increasing the speed and throughput of a system such as a semiconductor integrated circuit such as a microcomputer incorporating a nonvolatile memory or an IC card.
[0014]
The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.
[0015]
[Means for Solving the Problems]
The following is a brief description of an outline of typical inventions disclosed in the present application.
[0016]
That is, a reference voltage generation circuit that generates a reference voltage, a current-voltage conversion circuit that includes a resistor and a Zener diode connected in series with the resistor, and current control that can control a current that flows through the current-voltage conversion circuit And a voltage comparison circuit for controlling the current control means by comparing the voltage converted by the current-voltage conversion circuit with the reference voltage from the reference voltage generation circuit, and including the Zener diode. A constant voltage generation circuit configured to generate a constant voltage clamped by the variable resistance means, and the reference voltage generation circuit is connected in series to the variable resistance means and the temperature characteristic of the Zener diode is determined as a self-temperature characteristic. And a constant current circuit for supplying a current to the voltage generating means.
[0017]
According to the above-described means, since the temperature characteristic of the Zener diode is compensated by the temperature characteristic of the voltage generating means, a stable constant voltage can be generated regardless of temperature fluctuations. Moreover, an arbitrary constant voltage can be generated by setting the resistance value of the variable resistance means.
[0018]
Further, when the current-voltage conversion circuit has a plurality of Zener diodes in series, the reference voltage generation circuit is connected with the same number of voltage generation means as the Zener diodes of the current-voltage conversion circuit in series with the variable resistor. Good. Thus, the temperature characteristic of the Zener diode can be compensated relatively easily by the temperature characteristic of the voltage generating means, and a stable constant voltage can be generated regardless of temperature fluctuations.
[0019]
Alternatively, when the current-voltage conversion circuit includes n (n is a positive integer) Zener diodes in series, two or more resistance elements are connected in series with the Zener diodes, and resistance division of these resistance elements is performed. The voltage divided by 1 / n may be supplied to the voltage comparison circuit. Accordingly, the temperature characteristic of the Zener diode can be compensated by the temperature characteristic of the voltage generating means by one voltage generating means, and a stable constant voltage can be generated regardless of the temperature fluctuation.
[0020]
Further, the constant current circuit of the reference voltage generation circuit may be configured by a transistor to which a constant voltage is applied to a control terminal, and a resistance element connected in series with the transistor. As a result, since the current-voltage conversion circuit and the reference voltage generation circuit each have two sets of resistors in the same manner, even if the resistance value varies due to manufacturing variations, the voltage from the current-voltage conversion circuit and the reference voltage generation circuit Since the voltages supplied to the comparison circuits respectively change in the same manner, the voltage comparison circuits cancel each other as a change in phase, and a stable constant voltage can be generated regardless of manufacturing variations.
[0021]
Further, the variable resistance means of the reference voltage generating circuit includes a plurality of division resistors in series and a plurality of transistors connected in parallel to the respective division resistors and having a control signal applied to the control terminal. Can do. As a result, the constant voltage generated by the control signal after the circuit is completed can be adjusted or changed.
[0022]
The constant voltage generation circuit according to the present invention is preferably incorporated in a nonvolatile memory as a write voltage or erase voltage generation circuit, for example. In such a non-volatile memory, the accuracy of the generated voltage is increased, so that the writing time and erasing time are shortened.
[0023]
Further, a nonvolatile memory having the constant voltage generating circuit according to the present invention as a writing voltage or erasing voltage generating circuit is incorporated in a semiconductor integrated circuit such as a microcomputer. In such a semiconductor integrated circuit, since the accuracy of the generated voltage is increased, writing time and erasing time are shortened, and high-speed operation is possible.
[0024]
Further, a non-volatile memory having a constant voltage generating circuit according to the present invention as a writing voltage or erasing voltage generating circuit, or a semiconductor integrated circuit such as a microcomputer incorporating the same is mounted on a single insulating substrate to provide an IC card. A system like this is configured. In such a system, since the accuracy of the generated voltage is increased, the writing time and erasing time are shortened, and the throughput of the system is improved.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a constant voltage generating circuit according to the present invention.
[0026]
The constant voltage generating circuit of this embodiment includes a booster circuit 10 including a charge pump, resistors R1 and R2 connected in series between a power supply voltage terminal Vcc and an output terminal, and n-stage Zener diodes Dz1 to Dzn. Current voltage conversion circuit 20, reference voltage generation circuit 30 capable of setting the level of generated voltage, set reference voltage Vref and voltage converted by the current voltage conversion circuit (connection node n1 of resistors R1 and R2) Voltage comparison circuit 40, which is connected between the booster circuit 10 and the output terminal and is turned on and off by the output of the voltage comparator circuit 40, and is controlled from the current-voltage conversion circuit 20 by the booster circuit 10. It comprises switch means 50 for controlling the current drawn.
[0027]
Of these, the reference voltage generating circuit 30 comprises variable resistance means 31, a bipolar transistor 32 and a constant current circuit 33 connected in series between a power supply voltage terminal Vcc and a ground terminal. The base and the collector are combined to function as a voltage generating means (diode), and the emitter voltage of the transistor 32, that is, the potential of the connection node n2 between the bipolar transistor 32 and the constant current circuit 33 is used as the reference voltage Vref. It is supplied to the comparison circuit 40. The constant current circuit 33 includes a MOSFET Qc in series and a bias circuit 34 that biases the gate terminals of the resistors Rc and Qc to flow a constant current.
[0028]
Further, the bias circuit 34 converts a reference voltage Vbg such as about 1.2 V generated by a reference voltage generation circuit having no power supply voltage dependency such as a band gap reference circuit (not shown) to a voltage such as 0.6 V. A level shift circuit LSF that performs level shift and outputs, and the output voltage of the level shift circuit LSF is applied to the inverting input terminal (+), and the source voltage of the constant current MOSFET Qc is fed back to the non-inverting input terminal (−). Operational amplifier AMP.
[0029]
The output voltage of the operational amplifier AMP is applied as a bias voltage to the gate of the constant current MOSFET Qc, so that the source voltage of the MOSFET Qc is about 0.6 V, which is the same as the input potential of the inverting input terminal of the operational amplifier AMP. And the constant current Io is allowed to flow through the constant current MOSFET Qc. Further, the constant current Io is caused to flow through the variable resistor 31 and the diode-connected bipolar transistor 32 in the above-described series form. A constant voltage Vref determined by the base-emitter voltage of the bipolar transistor 32 is generated.
[0030]
In the constant voltage generation circuit of this embodiment, the reference voltage Vref generated by the reference voltage generation circuit 30 and the potential of the node n1 of the current-voltage conversion circuit 20 are compared by the voltage comparison circuit 40, and the potential of the node n1 is While the voltage is higher than the reference voltage Vref, the output of the comparison circuit 40 becomes high level, the switch means 50 is turned on, and a current is drawn out to the current-voltage conversion circuit 20 by the booster circuit 10. Further, when the potential of the node n1 of the current-voltage conversion circuit 20 becomes lower than the reference voltage Vref, the output of the comparison circuit 40 becomes low level, and the switch means 50 is turned off, and the drawing current from the current-voltage conversion circuit 20 by the booster circuit 10 is turned off. Shut off.
[0031]
By such a feedback operation, the constant voltage generation circuit of the embodiment is, for example, a Zener by a voltage drop due to the reverse voltage (about 6 V) of the Zener diodes Dz1 to Dzn of the current-voltage conversion circuit 20 and the current flowing through the resistors R1 and R2. When there are two diodes, a negative output voltage Vout that is 12 to 13 V lower than the power supply voltage Vcc is output, and when there are three diodes, a negative output voltage Vout that is 17 to 18 V lower than the power supply voltage Vcc is output. The level of the output voltage Vout can be arbitrarily set within a range in which the resistance value of the variable resistor 31 of the reference voltage generating circuit 30 is adjusted, as will be described later. Here, the output voltage Vout is set such that the Zener voltages of the Zener diodes Dz1 to Dzn are Vz, the voltage drop in the resistor R1 and the variable resistor 31 are Vr1 and Vr31, and the base-emitter voltage of the bipolar transistor 32 is VBE. And the following formula
Vout = Vcc- (nVz + Vr1 + VBE + Vr31)
It becomes a constant potential represented by
[0032]
Further, in the constant voltage generation circuit of this embodiment, the values of the series-type resistors R1 and R2 constituting the current-voltage conversion circuit 20 are Zener diodes Dz1 to Dzn connected in series with these resistors R1 and R2. When the number of n is n, (R1 + R2) / R1≈n is set. Thereby, the potential fluctuation of the node n1 due to the temperature characteristics of the n Zener diodes Dz1 to Dzn is offset by the potential fluctuation of the node n2 due to the temperature characteristics of the one bipolar transistor 32, and is stable regardless of the temperature fluctuation. Thus, the voltage Vout is output.
[0033]
That is, the constant voltage generating circuit of this embodiment has little influence on the output because the temperature change in the same phase with respect to the input of the voltage comparison circuit 40 is caused with respect to the characteristic change of the resistor R1 and the variable resistor 31 due to the change of the ambient temperature. At the same time, the temperature coefficient of resistance is considerably smaller than the temperature coefficient of Zener diodes and transistors. Therefore, the voltage at the node n1 has a positive temperature characteristic solely due to the temperature characteristics of the Zener diodes Dz1 to Dzn, and the voltage at the node n2 has a negative temperature characteristic due to the temperature characteristic of the bipolar transistor 32. In this embodiment, the influence of the temperature characteristics of the Zener diodes Dz1 to Dzn on the voltage at the node n1 is reduced to R1 / (R1 + R2) by the resistors R1 and R2. That is, when the change rate of the output voltage when the ambient temperature fluctuates by δT is δVout / δT, the temperature coefficients of the Zener diodes Dz1 to Dzn are δVz / δT, and the temperature coefficient of the bipolar transistor 32 is δVBE / δT.
δVout / δT = n (δVz / δT) * R1 / (R1 + R2) + δVBE / δT
It will be expressed as
[0034]
Here, the temperature coefficient δVz / δT of the Zener diode and the temperature coefficient δVBE / δT of the bipolar transistor can be regarded as almost opposite characteristics, that is, δVz / δT = −δVBE / δT, so n * R1 / (R1 + R2) = 1. It can be seen that the output voltage change rate δVout / δT becomes zero. Therefore, in this embodiment, as described above, the values of the resistors R1 and R2 are set to be (R1 + R2) / R1≈n. Therefore, δVout / δT = 0, and the output voltage Vout is constant regardless of temperature fluctuation, that is, has no temperature dependence.
[0035]
The values of the resistors R1 and R2 are not (R1 + R2) / R1 = n but are set to (R1 + R2) / R1≈n because the temperature coefficient δVz / δT of the Zener diodes Dz1 to Dzn and the bipolar transistor This is because the temperature coefficient δVBE / δT of 32 is not exactly equal, so that the resistance R1 and the resistance R2 are corrected in consideration of the difference. Incidentally, when the number of Zener diodes Dz1 to Dzn is 2 (n = 2), R1≈R2, and when 3 (n = 3), R2≈2R1.
[0036]
Further, as shown in FIG. 1, the constant voltage generating circuit of this embodiment has two voltages to be compared by the voltage comparison circuit 40, that is, resistors R1 and R2 on both sides of the connection node n1 and the connection node n2, respectively. Resistors 31 and Rc are connected. Therefore, even if the resistance value varies due to manufacturing variations in the process, the four resistances vary in the same manner. That is, as the value of one resistor increases, the value of the other resistor also increases, and as the value of one resistor decreases, the value of the other resistor also decreases. As a result, even if there is a manufacturing variation in resistance, the potential of the node n1 determined by the ratio of the resistors R1 and R2 and the potential of the node n2 determined by the ratio of the resistors 31 and Rc are relatively constant. Similarly, when the power supply voltage Vcc varies, the variation in the potential of the node n1 and the potential of the node n2 due to the variation is reduced by the resistance ratio of the resistors R1 and R2 and the resistors 31 and Rc, respectively. Therefore, a stable constant voltage Vout can be output even with respect to power supply voltage fluctuations. Accordingly, it is desirable that the resistance ratio of the resistors R1 and R2 and the resistance ratio of the resistors 31 and Rc are close to each other.
[0037]
The constant voltage generation circuit of this embodiment is configured so that the value of the resistor 31 can be changed. Hereinafter, a specific example of the resistor 31 having a variable resistance value will be described with reference to FIG.
[0038]
As shown in FIG. 3, the resistor 31 includes a plurality of divided resistors VR1 to VRm, and MOSFETs Qv1 to Qv1 to which control signals C1 to Cm are applied to the gate terminals in parallel with the divided resistors VR1 to VRm, respectively. The Qvm is provided.
[0039]
When the variable resistors 31 are turned off by the control signals C1 to Cm applied to the gate terminals of the MOSFETs Qv1 to Qvm connected in parallel with the divided resistors VR1 to VRm, the corresponding divided resistors are activated. When Qv1 to Qvm are turned on, both terminals of the corresponding divided resistor are short-circuited and the divided resistors are invalidated.
[0040]
The control signals C1 to Cm measure the level of the voltage output from the constant voltage generation circuit, determine the divided resistors VR1 to VRm to be activated so that the output voltage becomes a desired level, and respond to it The determined MOSFETs Qv1 to Qvm are determined to be turned on. Although not particularly limited, the control signals C1 to Cm are configured to be supplied from a setting circuit including a register or a nonvolatile memory element that is set to output a desired control signal. Instead of providing a setting circuit including a register or a non-volatile memory element that is set to output a desired control signal, a fuse element that determines input of those signals may be provided.
[0041]
As described above, the resistance value of the variable resistor 31 as a whole is set by the activated divided resistor, so that the level of the reference voltage Vref generated by the reference voltage generation circuit 30 is arbitrarily set. The voltage is supplied to the voltage comparison circuit 40 and compared with the voltage of the current-voltage conversion circuit 20, and the output of the switch means 50 is controlled to output a constant voltage Vout corresponding to the reference voltage Vref. Further, the variation of the resistance value (sheet resistance) of each resistor is stabilized by adjusting the resistance ratio of the resistors R1 and R2 and the resistance ratio of the resistors 31 and Rc so that the temperature dependency and the power supply voltage dependency are compensated. Will be output.
[0042]
In the embodiment shown in FIG. 3, x bipolar transistors Tr1 to Trx, in which a base and a collector are combined to act as a diode, are provided in parallel, and the number of transistors, that is, x is increased or decreased. By doing so, the emitter current can be adjusted.
[0043]
In this embodiment, the diode-connected bipolar transistor 32 is used, but a PN junction diode can be used instead of the transistor. However, in that case, it is desirable that the diode between the power supply voltage terminal Vcc and the node n2 and the variable resistor 31 be connected in the reverse direction of FIG. 1, that is, the diode should be on the power supply voltage terminal Vcc side. As shown in FIG. 1, when a bipolar transistor is used, the relationship between the resistor 31 and the transistor 32 may be on the power supply voltage Vcc side. Furthermore, the constant voltage generation circuit of the embodiment of FIG. 1 can also be applied when the booster circuit 10 is a constant current source or a constant current circuit provided outside the chip, thereby outputting a stable constant voltage. Can be made.
[0044]
FIG. 2 shows a second embodiment of the constant voltage generating circuit according to the present invention. The constant voltage generation circuit of the embodiment of FIG. 1 is an embodiment that outputs a negative constant voltage, whereas the constant voltage generation circuit of FIG. 2 is an embodiment that outputs a positive constant voltage. The configuration of the circuit is the same as that of the embodiment of FIG. 1 except that the relationship of the power supply voltage is reversed from that of the example, and therefore, the same or equivalent circuits and elements are denoted by the same reference numerals and detailed description is omitted. To do.
[0045]
FIG. 4 shows a third embodiment of the constant voltage generating circuit according to the present invention. In this embodiment, when there are two Zener diodes, the temperature dependence of the Zener diode is canceled by the temperature dependence of one bipolar transistor 32 of the reference voltage generation circuit 30 by the resistance ratio of the resistors R1 and R2. Instead, the reference voltage generation circuit 30 is provided with two bipolar transistors in series so that the temperature dependence of the Zener diode is offset by the temperature dependence of the two bipolar transistors 32a and 32b. It is. Since the temperature characteristic of the Zener diode is close to the temperature characteristic of the PN junction diode between the base and the emitter of the bipolar transistor, variation in the output voltage due to temperature variation can also be reduced by employing the configuration shown in FIG.
[0046]
FIG. 5 shows a fourth embodiment of the constant voltage generating circuit according to the present invention. The constant voltage generation circuit of the embodiment of FIG. 4 is an embodiment that outputs a negative constant voltage, whereas the constant voltage generation circuit of FIG. 5 is an embodiment that outputs a positive constant voltage. Since the circuit configuration is the same as that of the embodiment of FIG. 4 except that the relationship of the power supply voltage is reversed from the example, the same or equivalent circuit or element is denoted by the same reference numeral, and detailed description is omitted. To do.
[0047]
FIG. 6 shows a fifth embodiment of the constant voltage generating circuit according to the present invention. In this embodiment, in the voltage comparison circuit 40 shown in FIG. 1, when the output changes from the high level to the low level, the output voltage changes from the threshold voltage when the output changes from the low level to the high level. A circuit 60 in which an output signal such as a Schmitt circuit set so that the threshold voltage is low has a hysteresis characteristic is provided. As a result, it is possible to prevent the switch means 50 from being turned on and off unnecessarily due to a change in the output of the voltage comparison circuit 40 due to, for example, power supply noise.
[0048]
FIG. 7 shows a sixth embodiment of the constant voltage generating circuit according to the present invention. In the first to fifth embodiments, the switch means 50 is provided between the booster circuit 10 and the current-voltage conversion circuit 20, whereas in the embodiment of FIG. 7, the oscillation circuit OSC is charged as a booster circuit. An AND gate GT for supplying or blocking the clock signal φc supplied to the pump 10 is provided. When the clock signal φc is cut off, the booster circuit 10 stops the boosting operation, and the current drawn from the current-voltage converter circuit 20 decreases, so that the AND gate GT is the same as the switch means 50 in the first to fifth embodiments. Will work. Although not particularly limited, in this embodiment, an oscillation circuit OSC that generates a clock signal φc is provided on the same chip as the constant voltage generation circuit.
[0049]
Note that, instead of the AND gate GT in this embodiment, the same switch means (for example, MOSFET) as in the first to fifth embodiments may be used to control the clock supply to the booster circuit. In the first to fifth embodiments, instead of providing the switch means 50 between the booster circuit 10 and the current-voltage converter circuit 20, the clock signal φc is supplied to or cut off from the preceding stage of the booster circuit 10. A gate G may be provided.
[0050]
FIG. 8 shows an electrically writable / erasable EEPROM (electrically erasable programmable read) as an example of a nonvolatile memory in which the constant voltage generating circuit according to the present invention is applied as a writing voltage or erasing voltage generating circuit. A schematic configuration of (only memory) is shown. In FIG. 8, reference numeral 11 denotes a memory array in which memory cells as nonvolatile memory elements made of MOSFETs having floating gates are arranged in a matrix, and 12 is based on write data input from the outside via the I / O buffer 13. And a write / erase circuit for writing and erasing the memory array 11.
[0051]
Reference numeral 14 denotes an address register for holding an address signal input from the outside via the I / O buffer 13, and 15 corresponds to the X address taken into the address register 14 from the word lines in the memory array 11. An X decoder for selecting one word line, 16 a Y decoder for decoding a Y address fetched into the address register 14 and selecting a data line corresponding to the Y address, and 17 a data read from the memory cell array 11 Is a sense amplifier that amplifies and outputs.
[0052]
Further, in the flash memory circuit of this embodiment, in addition to the above circuit blocks, control signals such as an external chip selection signal CS and read / write control signal R / W are used as control signals to the respective circuit blocks in the memory. A control circuit 18 for conversion, a power supply circuit 70 for generating a voltage required inside the chip, such as a write voltage, an erase voltage, a read voltage, and a verify voltage based on a power supply voltage Vcc supplied from the outside, and an operation state (mode) of the memory ), A power supply switching circuit 71 or the like that selects a desired voltage from these voltages and supplies the selected voltage to the write / erase circuit 12, the X decoder 15, the Y decoder 16, or the like is provided.
[0053]
The constant voltage generation circuit according to the present invention described with reference to FIGS. 1 to 7 is provided in the power supply circuit 70 as a write voltage or erase voltage generation circuit. The nonvolatile memory having the constant voltage generation circuit according to the present invention as the write voltage or erase voltage generation circuit has the advantage of shortening the write time and the erase time because the accuracy of the generated voltage is increased. .
[0054]
FIG. 9 shows a schematic configuration of a microcomputer as an example of a semiconductor integrated circuit incorporating the nonvolatile memory.
[0055]
In FIG. 9, NVM is a non-volatile memory circuit having the configuration as shown in FIG. 8, and CNT is a memory control circuit that controls writing, erasing, reading (including verify reading), etc. with respect to the memory circuit NVM. (Memory controller), CPU is a central processing unit that decodes program instructions and performs various operations and data processing, RAM is a high-speed random access memory that temporarily stores data and provides a work area for the central processing unit CPU, BUS is A bus connecting the central processing unit CPU and the memory circuit NVM, the memory controller CNT, and the high-speed memory RAM, BSC is a bus controller as a system control circuit for controlling the occupation right of the bus. In this system, the non-volatile memory NVM is used for storing programs executed by the CPU and fixed data used in the programs.
[0056]
Although not particularly limited, for example, the control signals C1 to Cm supplied to set the generated voltage, that is, the resistance value of the variable resistor 31, in the reference voltage generating circuit 30 constituting the constant voltage generating circuit of FIG. The control register CTR or the like provided in the CNT is provided to the constant voltage generation circuit in the power supply circuit 70 provided in the nonvolatile memory NVM. In a semiconductor integrated circuit such as a microcomputer incorporating a non-volatile memory having the constant voltage generating circuit according to the present invention as a writing voltage or erasing voltage generating circuit, the accuracy of the generated voltage is increased. There is an advantage that the time and the erasing time are shortened and high speed operation is possible.
[0057]
Although not shown in FIG. 9, in the case of a microcomputer such as a single chip microcomputer, in addition to the above circuit blocks, DMA (direct memory access) between an internal memory and an external memory, etc. DMA transfer control circuit for controlling transfer, interrupt control circuit for determining the generation and priority of interrupt requests to the CPU and making an interrupt, serial communication interface circuit for serial communication with external devices, various timer circuits, analog An A / D conversion circuit for converting a signal and a digital signal, a watchdog timer for system monitoring, an oscillator for generating a clock signal necessary for system operation, and the like are provided as necessary.
[0058]
FIG. 10 shows a configuration example of an IC card (memory card) as an example of a system using a nonvolatile memory. The IC card of this embodiment is not particularly limited, but the n non-volatile memory chips FM1 to FMn, the interface and bus switching with the outside, and the formation of selection signals for each memory chip based on address signals and control signals A controller chip CONT having functions such as ECC code generation and checking, and a microprocessor CPU that performs writing and reading control on the nonvolatile memory chip based on an externally supplied command are mounted on the printed circuit board 100. The whole is molded by resin or the like.
[0059]
The controller chip CONT is connected to the nonvolatile memory chips FM1 to FMn via an address & control bus 111 and a data bus 112 formed on the substrate 100, and is inserted into a card slot such as an external personal computer main body. The non-volatile memory chips FM1 to FMn are connected to the external terminal 114 and are configured to be accessed via the controller chip CONT. Control signals may be supplied from the microprocessor CPU to the memory chips FM1 to FMn.
[0060]
In this embodiment, although not particularly limited, the constant voltage generation circuit according to the present invention is a power supply circuit that generates a write voltage Vw, a read voltage Vr, an erase voltage Ve, a write verify voltage Vwv, an erase verify voltage Vev, and the like. The power supply voltage generated in the controller chip CONT is supplied to the nonvolatile memory chips FM1 to FMn via the power supply line group 113. Reference numeral 116 denotes an external power supply terminal to which the power supply voltage Vcc supplied to the controller chip CONT and the nonvolatile memory chips FM1 to FMn is applied, and 117 denotes an external ground terminal to which a ground potential is applied.
[0061]
The function of the controller chip CONT may be constituted by one or several semiconductor chips, but may be constituted by one gate array. Further, instead of mounting the memory chips FM1 to FMn on the substrate from the controller chip CONT and the microprocessor CPU, an IC card on which a microcomputer chip as shown in FIG. 9 is mounted is also possible.
[0062]
Like an IC card in which a non-volatile memory having a constant voltage generating circuit according to the present invention as a writing voltage or erasing voltage generating circuit or a semiconductor integrated circuit such as a microcomputer incorporating the same is mounted on a single insulating substrate In such a system, since the accuracy of the generated voltage is increased, there is an advantage that the writing time and erasing time are shortened and the throughput of the system is improved.
[0063]
The invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Nor. For example, in the above embodiment, the EEPROM and the semiconductor integrated circuit incorporating the same have been described. However, the present invention is not limited to this, and the present invention can be similarly applied to a flash memory and a semiconductor integrated circuit incorporating the same.
[0064]
In the above description, the case where the invention made by the present inventor is applied to a constant voltage generation circuit built in a nonvolatile memory which is a field of use as a background has been described. However, the present invention is not limited thereto. In addition, it can be widely used in a semiconductor integrated circuit for generating a constant voltage or a reference voltage for generating a constant voltage or a semiconductor integrated circuit incorporating a constant voltage generating circuit.
[0065]
【The invention's effect】
The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
[0066]
That is, according to the present invention, a constant voltage generating circuit capable of generating a constant voltage regardless of temperature change is obtained. In addition, a constant voltage generation circuit capable of generating a constant voltage regardless of power supply fluctuations can be obtained. Furthermore, a constant voltage generating circuit capable of generating a constant voltage regardless of manufacturing variations can be obtained.
[0067]
Further, when the constant voltage generation circuit of the present invention is built in a nonvolatile memory as a write voltage or erase voltage generation circuit, the write / erase time can be shortened. Furthermore, in a system such as a semiconductor integrated circuit such as a microcomputer or an IC card incorporating a nonvolatile memory having the constant voltage generating circuit of the present invention as a writing voltage or erasing voltage generating circuit, the speed is increased and the throughput is improved. There is an effect that it can be achieved.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram showing an embodiment of a constant voltage generating circuit according to the present invention.
FIG. 2 is a circuit configuration diagram showing another embodiment of the constant voltage generating circuit according to the present invention.
3 is a circuit diagram showing a more specific configuration example of the constant voltage generation circuit of FIG. 1; FIG.
FIG. 4 is a circuit configuration diagram showing a third embodiment of the constant voltage generating circuit according to the present invention.
FIG. 5 is a circuit configuration diagram showing a fourth embodiment of a constant voltage generating circuit according to the present invention.
FIG. 6 is a circuit configuration diagram showing a modification of the constant voltage generation circuit according to the present invention.
FIG. 7 is a circuit configuration diagram showing another modification of the constant voltage generating circuit according to the present invention.
FIG. 8 is a block diagram showing a configuration example of a nonvolatile memory in which a constant voltage generation circuit according to the present invention is built as a circuit for generating a write voltage and an erase voltage.
FIG. 9 is an overall block diagram showing a schematic configuration of an example of a microcomputer as an example of a semiconductor integrated circuit incorporating a nonvolatile memory to which a constant voltage generating circuit according to the present invention is applied.
FIG. 10 is a block diagram showing an example of an IC card incorporating a nonvolatile memory to which the constant voltage generation circuit according to the present invention is applied.
FIG. 11 is a circuit configuration diagram showing an example of a constant voltage generation circuit studied prior to the present invention.
[Explanation of symbols]
11 Memory array
12 Programming / erasing circuit
13 I / O buffer
14 Address register
15 line decoder
16 column decoder
17 sense amplifier
18 Control circuit
70 Power supply circuit
71 Power supply switching circuit
10 Booster circuit
20 Current-voltage conversion circuit
30 Reference voltage generator
32 Voltage generation means
33 Constant current circuit
40 Voltage comparison circuit
50 Current control means

Claims (8)

A reference voltage generation circuit for generating a reference voltage; a current-voltage conversion circuit comprising a resistor and a Zener diode connected in series with the resistor; and a current control means capable of controlling a current flowing through the current-voltage conversion circuit; A voltage comparison circuit that controls the current control means by comparing the voltage converted by the current-voltage conversion circuit with the reference voltage from the reference voltage generation circuit, and is clamped by the current-voltage conversion circuit including the Zener diode A constant voltage generation circuit configured to generate a constant voltage, wherein the reference voltage generation circuit is connected in series to the variable resistance means and the variable resistance means, and compensates the temperature characteristics of the Zener diode by its own temperature characteristics. A constant voltage generating circuit comprising a possible voltage generating means and a constant current circuit for supplying a current to the voltage generating means. When the current-voltage conversion circuit has a plurality of zener diodes in series, the reference voltage generation circuit has the same number of voltage generation means as the zener diodes of the current-voltage conversion circuit connected in series with the variable resistance means. The constant voltage generation circuit according to claim 1, wherein: When the current-voltage conversion circuit has n (n is a positive integer) Zener diodes in series, two or more resistance elements are connected in series with the Zener diodes, and the resistance elements of those resistance elements are divided by 1 2. The constant voltage generation circuit according to claim 1, wherein a voltage divided by / n is supplied to the voltage comparison circuit. 4. The constant current circuit of the reference voltage generation circuit includes a transistor having a constant voltage applied to a control terminal, and a resistance element connected in series with the transistor. Constant voltage generator circuit. The variable resistance means of the reference voltage generation circuit is composed of a plurality of division resistors in series and a plurality of transistors connected in parallel to the respective division resistors and having a control signal applied to the control terminal. The constant voltage generation circuit according to claim 1, 2, 3, or 4. A nonvolatile memory comprising the constant voltage generation circuit according to claim 1 as a circuit for generating a write voltage or an erase voltage to be applied to a storage element. 7. The non-volatile memory according to claim 6, a memory control circuit for controlling the non-volatile memory to perform write and read operations, and system control for forming a control signal for controlling an operation state of the non-volatile memory A semiconductor integrated circuit comprising a circuit. 8. The semiconductor integrated circuit according to claim 7, the nonvolatile memory according to claim 6, a memory control circuit for controlling the nonvolatile memory to perform write and read operations, and an operation state with respect to the nonvolatile memory. A system characterized in that a system control circuit for forming a control signal to be controlled is mounted on one insulating substrate.

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