JPS5933059Y2 - Volatile memory power supply circuit - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a power supply circuit for volatile memory.

Volatile memory elements lose their written information when the device power is cut off, so when the power is cut off, information is always stored and maintained by supplying power for information storage from a separate battery. configuration has been adopted.

As an example, as shown in FIG. 1, a power supply line VDD of a volatile memory integrated circuit 1 having a CMO8 (complementary MO8) configuration is supplied with a minimum voltage (2 to 3V) is applied via the unidirectional diode 3.

On the other hand, the device power source 1B is also a unidirectional diode 4.
It is supplied to the memory power supply line VDD via the power supply line VDD.

Here, only the device power supply 1B is supplied to the IC circuits 5 other than the memory 1, but the voltage required for the operation of these memory IC circuits 1 and other IC circuits 5 is +5■,
Since the memory circuit 1 must be supplied with a power supply voltage of 10B through the diode 4 for backflow prevention, the power supply voltage is set to a voltage higher than the forward voltage VB (0.5 to 0.7V) of the diode. It is set to 10B.

Therefore, in order to supply +5■ to the IC circuit 5, a diode 6 is similarly used to reduce the voltage drop (0.5 to 0.7 V).
).

In such a configuration, only one power source is required as the device power source 10B, but since the voltage drop across the diodes 4 and 6 varies depending on the current flowing through them, the voltage applied to the memory and IC circuit 5 may vary due to variations in the circuit current of the memory and IC circuit 5. The disadvantage is that the applied voltage fluctuates.

In order to eliminate this drawback, as shown in Fig. 2, there is a configuration in which the device is powered by two power sources, one of which is supplied independently to the IC circuit 2, but this increases the size of the device and increases costs. There is a drawback.

An object of the present invention is to provide a power supply circuit for a volatile memory that has no voltage fluctuation and has an extremely simple circuit configuration.

The present invention will be explained below with reference to the drawings.

FIG. 3 is a circuit diagram of an embodiment of the present invention, in which the voltage (2 to 3 V) of the backup battery 2 is connected to the power supply line VDD of the volatile memory IC circuit 1 through a unidirectional diode element 3 for preventing backflow. The same way as in the case of FIGS. 1 and 2 is applied to store and hold information.

The device power supply 1B is directly applied to the other IC circuit 5, and the PNP I for switching is applied to the memory 1.
- Power is applied via the transistor.

That is, a power supply element B is supplied to the emitter of the transistor 6, and its collector output is applied to the power supply line VDD of the memory 1, and a bias circuit section 10 that generates a base bias voltage is provided at its control (base) electrode. ing.

As shown in the figure, this bias circuit 10 has a common emitter N
It consists of a PN transistor and resistors R1 to R3.

Also, the unidirectional diode 8 changes the voltage of the battery 2 to PNP.
It is applied to the base of the I-range star.

In this configuration, when the device power is on, the power supply voltage terminal B is supplied to the emitter of the transistor 6, and since the transistor 7 of the bias circuit 10 is on, the base of the transistor 6 is grounded through the resistor R1. That will happen.

Therefore, the switching transistor 6 will be turned on at or near saturation to supply the power source B to the memory 1 with extremely low impedance.

At this time, the voltage drop across transistor 6 is 0.2 to 0.3V.
Therefore, the voltage drop caused by the switching element 6 is extremely low and can be ignored with respect to the power supply voltage.

When power supply B is off, both transistors 6 and 7 are off, so a low voltage is supplied from backup battery 2 to memory 1 via diode 3 to maintain information.

At this time, a voltage is supplied from the battery 2 to the base of the switching transistor 6 via the diode 8, so that the transistor 6 is completely reverse biased, and a reverse current flowing from the collector to the emitter of the transistor can be blocked.

If a CMO8 circuit is used as the memory 1, a current of several μA is required to maintain information, so a small dry battery can be used for backup.

Furthermore, the battery 2 can be equipped with a power storage element such as a capacitor for short-term memory retention, and the point is to use a power storage means as a backup field.

Furthermore, the memory circuit is not limited to CMO8, and various types of volatile memory can be used.

As described above, according to the present invention, it is possible to effectively utilize the power supply voltage element B, and stable circuit operation can be expected with a single power supply and no fluctuation thereof.

Furthermore, it is possible to completely block the reverse outflow current caused by the switching element 6, and thus the current loss of the backup power source can be suppressed.

[Brief explanation of the drawing]

1 and 2 are diagrams showing an example of a conventional memory power supply circuit, and FIG. 3 is a circuit diagram of an embodiment of the present invention. Explanation of symbols of main parts, 1... Volatile memory,
2... Battery, 3, 8... Diode, 6... Switching transistor, 10...
...Bias circuit.

Claims (1)

[Scope of utility model registration request] A power supply circuit for a volatile memory, comprising: a power supply that can be turned on and off; a transistor that supplies the power to a power supply line of the memory; and when the power supply is turned on, the transistor operates at or near saturation. bias means for applying a sufficient voltage to the control electrode thereof; a power storage means for generating a voltage lower than the power supply voltage; and a first unidirectionality for supplying the voltage of the power storage means to the power supply line of the memory. A power supply circuit for a volatile memory, comprising: a second unidirectional element that supplies the voltage of the power storage means to a control electrode of the transistor.