JPH0589689A - Write voltage generator for eeprom - Google Patents

Abstract

PURPOSE:To write data by using an EEPROM as a nonvolatile memos even in a low power type small-sized apparatus and particularly a solar type small- sized apparatus. CONSTITUTION:A write voltage holding capacitor C4 is connected between a Vdd power source terminal of an EEPROM 1 and a high potential side terminal of a DC power source Vs. The capacitor C4 is charged by a charging circuit 4. The circuit 4 has a capacitor C3 having a smaller capacity than that of the capacitor C4, and sequentially transfers charge sucked up to the capacitor C3 from the power source Vs according to the switching operations of transistors P1, N1, N2, N3 to step up a voltage across the capacitor Cr to a voltage higher than the power source voltage Vs. The voltage held in the capacitor C4 is applied as a write voltage Vprog to the EEPROM 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an EEPROM (Electr
TECHNICAL FIELD The present invention relates to an EEPROM write voltage generation circuit that supplies a data write voltage to an erasably programmable ROM (ROM), and more particularly to an EEPROM write voltage generation circuit suitable for a device using a small power source such as a solar cell and a button battery.

[0002]

2. Description of the Related Art A digital caliper, a digital micrometer, which displays measured values on a liquid crystal display device,
A small displacement measuring device such as a height gauge is generally of a low power consumption type using a capacitance type displacement sensor or the like. For this reason, recently, a solar type displacement measuring device using a solar cell as a power source has also been developed. on the other hand,
In this type of small displacement measuring device, for example, in the absolute type, an EEPROM is used as a non-volatile memory for storing origin information and the like. Since a general EEPROM requires a DC voltage of about 3V for writing,
This type of equipment requires a DC power supply of 3 V or higher.

[0003]

However, in digital calipers, digital micrometer, etc., it is desirable that the number of button batteries (1.5 V) used in order to reduce the size and power consumption of the device be as small as possible. Be done. Also,
Even in the solar type displacement measuring device, since the electric power that can be supplied is limited, it is desirable that the power source voltage is as low as possible. Therefore, in such an apparatus, there is a problem that data cannot be written in the EEPROM.

The present invention has been made in order to solve such a problem. Even in a low power type small device, particularly a solar type small device, an EEPROM is used as a nonvolatile memory to write data. It is an object of the present invention to provide an EEPROM write voltage generation circuit capable of performing the above.

[0005]

EEPRO according to the present invention
The M write voltage generation circuit is a write voltage generation circuit for an EEPROM that supplies a write voltage to a write voltage supply terminal of the EEPROM, and a DC power supply that outputs a power supply voltage lower than the write voltage for the EEPROM. A writing voltage holding capacitor connected between one terminal of the DC power supply and the writing voltage supply terminal of the EEPROM, and the writing operation by charging the capacitor from the writing voltage supply terminal side. And a charging circuit for boosting the voltage of the voltage supply terminal to the writing voltage of the EEPROM.

[0006]

According to the present invention, one terminal of the DC power source and the EE
The charge is supplied from the charging circuit to the write voltage holding capacitor connected between the PROM and the write voltage supply terminal,
The voltage across the capacitor is raised above the power supply voltage to generate the write voltage. Normally, the writing time of EEPROM is on the order of several tens of ms, so several tens of μF
With the use of the capacitor, the writing can be completed before the voltage drops significantly. Therefore, according to the present invention, it is possible to perform the writing operation to the EEPROM even in a circuit or a small solar system that uses one button battery having a low power supply voltage, for example, 1.5V.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an EE according to an embodiment of the present invention.
It is a circuit diagram which shows the structure of the write voltage generation circuit of PROM. In FIG. 1, an EEPROM 1 is a non-volatile memory that retains written data even when the power is turned off, and its Vdd power supply terminal and Vss power supply terminal are, for example, a high potential side of a DC power supply Vs of 1.5 V, respectively. It is connected to the terminal and the low potential side terminal. A capacitor C4 for holding the write voltage is connected between the Vdd power supply terminal of the EEPROM 1 and the high potential side terminal of the DC power supply Vs.

The capacitor C4 is adapted to be charged by the charging circuit 4. The charging circuit 4 includes a capacitor C3 having a smaller capacity than that of the capacitor C4, and sequentially transfers the electric charge absorbed from the DC power source Vs to the capacitor C3 to the capacitor C4 in accordance with the switching operation of the transistor switch. That is, a P-channel MOS transistor P1 is provided between one terminal of the capacitor C3 and the high potential side terminal and the low potential side terminal of the DC power source Vs.
And an N-channel MOS transistor N1 are connected, and between the other terminal of the capacitor C3 and the high potential side terminal of the DC power source Vs and the write voltage (Vprog) supply terminal of the EEPROM 1, respectively, N-channel MOS transistors N2 and N3 are connected.
Are connected. The transistors P1, N1 and N3 are driven by the clock signal CLK and the transistor N2
Is driven by a signal obtained by inverting the clock signal CLK by the inverter 3. The controller 2 supplies the driving clock CLK and the write data DI to the EEPROM 1 and executes a desired process based on the write data DO read from the EEPROM 1.

Next, the writing operation of the EEPROM 1 in the circuit thus constructed will be described. Figure 2
It is a figure which shows the charging voltage curve of the capacitor C4. That is,
First, prior to the supply of the write voltage to the EEPROM 1, the clock signal CLK is supplied to the transistors P1, N1, N2,
When supplied to N3, charging of the capacitor C4 is started. That is, when the clock signal CLK is at "L" level, the transistors P1 and N2 are turned on and the transistors N1 and N3 are turned off, so that the capacitor C3 is supplied with electric charges from the DC power source Vs to charge C3. Then, when the clock signal CLK goes to "H" level, the transistors P1 and N2 are turned off and the transistors N1 and N3 are turned on, so that the charges charged in the capacitor C3 are transferred to the capacitor C4 and the Vprog terminal is pulled down. When this is repeated, as shown in FIG.
It is pulled down from the potential to exceed the Vss potential and further to the −Vdd potential. That is, the voltage across the capacitor C4 is boosted to twice the supply voltage Vdd of the DC power supply Vs.

In this state, by supplying the write data DI from the controller 2, it is possible to write to the EEPROM 1. At this time, if the writing time is several tens of ms, the capacitor C4 has several tens of μF.
With this, the write operation can be completed before the write voltage drops significantly. After that, the clock signal C
When the supply of LK is stopped, the charging voltage of the capacitor C4 gradually decreases due to the leakage current.
It suffices to supply the clock signal CLK to the charging circuit 4 again when writing to M1 becomes necessary.

FIG. 3 is a block diagram showing an embodiment in which the present invention is applied to a solar type small measuring device. The power supply voltage Vd supplied from the solar cell 11 is the diode D1.
It is given to both ends of the capacitor C1 via. The power supply voltage Vd supplied to the capacitor C1 is supplied to the regulator 12. The regulator 12 stabilizes the fluctuating power supply voltage Vd of the solar cell 11 to the regulator voltage Vreg together with the capacitor C2, and the controller 1
3 and EEPROM 14. This prevents an excessive voltage from being applied to the controller 13 and the EEPROM 14. The controller 13 performs a process for detecting a predetermined displacement amount, for example, a length, outputs a charge control command charge to the charging circuit 15, and exchanges data with the EEPROM 14 and other external circuits (not shown). It is a circuit that exchanges. Further, the voltage detection circuit 16 monitors the regulator voltage Vreg during charging when generating the writing voltage of the EEPROM 14, and charges the detection signal V2det when the regulator voltage Vreg is equal to or higher than a predetermined voltage value. Output to the circuit 15.

The charging circuit 15 and the capacitor C3 are the same circuits as the charging circuit 4 described above, and supply the writing voltage Vprog of the EEPROM 14 to the externally attached capacitor C4. Further, the voltage detection circuit 17 is a circuit for monitoring the charging voltage of the capacitor C4, and supplies a detection signal V4det to the controller 13 when this voltage exceeds a predetermined value necessary for writing to the EEPROM 14.

According to this circuit, when the charging control signal charge is output from the controller 13 to the charging circuit 15, the charging circuit 15 starts charging the capacitor C4. Then, when the voltage detection circuit 17 detects that the charging voltage to the capacitor C4 has reached the predetermined potential required for writing to the EEPROM 1, the detection signal V4det is sent to the controller 13.
Is output. As a result, the controller 13 causes the EEP
Since the write data DI is output to the ROM 14, EEPR
The OM 14 is given an appropriate write voltage Vprog and starts writing data.

When the solar cell 11 is used as the power source as in this embodiment, the charging circuit 15 is used when the output of the solar cell 11 is insufficient, for example, in an environment where the light amount is small.
The regulator voltage Vreg drops when the switch is activated. However, in this embodiment, the regulator voltage Vreg is monitored by the voltage detection circuit 16 to obtain the regulator voltage Vreg.
Since the operation of the charging circuit 15 is stopped when reg does not reach the predetermined level, it is possible to prevent the regulator voltage Vreg from dropping more than necessary and affecting the controller 13 and the like.

The present invention is not limited to the above embodiment. For example, when charging the positive potential side of the capacitor C4, in the circuit of FIG.
Change the OS transistor to an N-channel MOS transistor and replace the N-channel MOS transistor with a P-channel MO transistor.
The same effect can be obtained by changing to an S transistor.

[0016]

As described above, according to the present invention, the charging voltage holding capacitor connected between one terminal of the DC power supply and the writing voltage supply terminal of the EEPROM is connected to the charging circuit. Since electric charges are supplied and the voltage across the capacitor is raised above the power supply voltage to generate the write voltage, in a circuit or a small solar system that uses one 1.5V button battery as the power supply voltage, for example. EE
It becomes possible to write to the PROM.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a write voltage generation circuit of an EEPROM according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a charging curve of a write voltage holding capacitor in the same circuit.

FIG. 3 is a waveform diagram showing an example of a drive signal supplied to the sensor.

FIG. 4 is a block diagram of a writing circuit of an EEPROM according to a second embodiment of the present invention.

[Explanation of symbols]

1,14 ... EEPROM, 2,13 ... controller,
4, 15 ... Charging circuit, 11 ... Solar cell.

[Procedure amendment]

[Submission date] September 24, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief explanation of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a circuit diagram of a write voltage generation circuit of an EEPROM according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a charging curve of a write voltage holding capacitor in the same circuit.

[Figure 3] Applying the same circuit to a solar-type small measuring device
It is a block diagram which shows the embodiment .

[Explanation of Codes] 1,14 ... EEPROM, 2, 13 ... Controller,
4, 15 ... Charging circuit, 11 ... Solar cell.

Claims (2)

[Claims] 1. In a write voltage generation circuit of an EEPROM for supplying a write voltage to a write voltage supply terminal of an EEPROM, a DC power supply for outputting a power supply voltage lower than the write voltage of the EEPROM, and a DC power supply of this DC power supply. A capacitor for holding a write voltage connected between one terminal and the write voltage supply terminal of the EEPROM, and a capacitor for charging this capacitor from the write voltage supply terminal side, A writing voltage generation circuit for an EEPROM, comprising: a charging circuit for boosting a voltage up to the writing voltage for the EEPROM. 2. In a write voltage generation circuit of an EEPROM for supplying a write voltage to a write voltage supply terminal of an EEPROM, a solar cell which outputs a power supply voltage lower than the write voltage of the EEPROM, and a solar cell of the solar cell A capacitor for holding a write voltage connected between one terminal and the write voltage supply terminal of the EEPROM, and a capacitor for charging this capacitor from the write voltage supply terminal side, A charging circuit for boosting the voltage to the writing voltage of the EEPROM; and a voltage detecting circuit for stopping the operation of the charging circuit when the power supply voltage of the solar cell is lower than a predetermined voltage. EEPROM write voltage generation circuit.