JPH1040351A - IC memory card - Google Patents

Abstract

(57) [Problem] To provide an IC memory card that retains the stored content of a volatile memory built in by a battery, with the object of improving the reliability of retaining the stored content by the battery and saving power. SOLUTION: A connection unit 1 connected to an external device 2, a memory unit 3, a battery 4, a power supply control unit 5 for controlling switching of a power supply, a control unit 6 for controlling the memory unit 3, and a voltage dividing circuit 11.
A switch circuit 12 for supplying a terminal voltage of the battery 4 to the voltage dividing circuit 11, and a first circuit for detecting an output voltage of the voltage dividing circuit 11.
, And a battery voltage detection unit 7 including an output circuit 14 that receives an output signal of the first voltage detection circuit 13 and supplies the output signal to the connection unit 1. It is possible to provide an IC memory card which can extend the life of the battery 4 without malfunction of the voltage detection circuit 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC memory card having a built-in battery for storing data.

[0002]

2. Description of the Related Art In recent years, IC memory cards include RAM, R
It is widely used as a portable storage medium incorporating a memory LSI such as an OM.

At this time, in the case of an IC memory card having a built-in volatile memory, it is necessary to back up the battery using a battery in order to retain the memory. In order to enhance the reliability, the terminal voltage of the battery is detected to detect the battery voltage. It is necessary to constantly monitor the state of discharge and prevent loss of stored contents due to a decrease in discharge capacity.

[0004] Referring to the drawings, a description will be given of a mechanism for protecting the stored contents of a conventional IC memory card.

In FIG. 4, reference numeral 15 denotes a connection unit, which is supplied with power from an external device 16 and transmits and receives signals. Reference numeral 17 denotes a memory unit composed of a memory LSI, which includes at least one static RAM or dynamic RAM which is a volatile memory for reading and writing data. Reference numeral 18 denotes a battery, which is a backup power supply that retains the contents stored in the volatile memory of the memory unit 17 when power is not supplied from the external device 16 via the connection unit 15. Reference numeral 19 denotes a power control unit which supplies a power supply to the memory unit 17 to the external device 16.
From the battery 18 or from the battery 18 to the external device 16. Reference numeral 20 denotes a memory control unit, and a connection unit 15
The memory unit 17 is controlled by a signal from the external device 16 via the. Reference numeral 21 denotes a battery voltage detection unit which detects a terminal voltage of the battery 18 and supplies a detection result to the connection unit 15 so that the external device 16 receives the information and grasps the state of the battery 18 so that an IC memory is detected. Each signal for protecting the stored contents of the card is output.

In the circuit diagram of the battery voltage detecting section 21 shown in FIG. 5, reference numeral 21A is a reference voltage generator, and 21B, 21C,
21D and 21E are resistors, and 21F and 21G are voltage comparators. When the output signals of the voltage comparators 21F and 21G are both at a high level, a signal indicating that the terminal voltage of the battery 18 is normal and the data of the memory unit 17 is stored and output is output to the connection unit 15. Upon receiving this signal, the external device 16 informs the user that the battery voltage is normal. When the battery voltage decreases with the use of the battery 18 and only the output signal of the voltage comparator 21F becomes low level, the terminal voltage of the battery 18 decreases, and it is necessary to replace or charge the battery 18. Show. At this time, the memory unit 17 is still stored and held by the battery 18, and this information is also transmitted from the external device 16 to the user in the same manner as in the normal state. And the voltage comparators 21F and 2
When both of the 1G output signals become low level, the terminal voltage of the battery 18 further decreases, and it is necessary to replace or charge the battery 18, and the signal indicating that the memory unit 17 has not been able to store the data. Is transmitted from the external device 16 to the user in the same manner as in the normal state.

[0007]

However, in the above-mentioned conventional configuration, power is consumed by the resistor 21E which is not related to the memory holding operation shown in FIG. This allows
The limited electric capacity of the battery cannot be used effectively, which leads to a shorter life of the battery. For example, 128K byte SRAM
In the card, the backup current of the low power consumption type 1 Mbit SRAM is set to 1 μA, and 1 MΩ is connected to the resistor 21 </ b> E.
And the terminal voltage of the battery is 3 V, the resistor 21E
The discharge current of the battery becomes 3 μA, and the battery life is reduced to about １ ／ as compared with the case where the resistor 21E is not present.

However, simply reducing the resistance value of the resistor 21E or removing the resistor 21E causes the input terminals of the voltage comparators 21F and 21G to be open when no batteries are installed, and causes the input to occur. A malfunction occurs due to the influence of the bias current, the influence of noise caused by opening the high impedance input, and the like.
And the output signal of 21G becomes high level, and it is determined that the terminal voltage of the battery is normal and the data of the memory unit is normally stored and held even though the battery is not mounted. There was a case.

The present invention has been made to solve such a conventional problem, and can realize a battery voltage detecting section which extends the life of a battery and does not cause a malfunction even when a battery is not mounted. It is an object to provide a highly reliable IC memory card.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a connection unit receiving power from an external device and transmitting and receiving a signal, a memory unit including at least one volatile memory, A memory control unit that controls the memory unit according to a signal from the external device; a battery that stores and holds volatile memory of the memory unit; and a power control unit that controls switching between power supply from the external device and the battery. And a battery voltage detection unit that detects a terminal voltage of the battery, wherein the battery voltage detection unit includes a voltage dividing circuit, a switch circuit that supplies a terminal voltage of the battery to the voltage dividing circuit, and a voltage dividing circuit. A first voltage detection circuit for detecting an output voltage; and an output circuit for receiving an output signal of the first voltage detection circuit and supplying a signal to the connection unit, thereby suppressing power consumption. When the battery is not mounted, the voltage dividing circuit prevents the input terminal of the voltage detection circuit from being opened, and this configuration can extend the life of the battery, and can be used when the battery is not mounted. Also, malfunction can be prevented.

In the above invention, the power supply control section includes a second voltage detection circuit for detecting a power supply voltage supplied from an external device, a pulse circuit for generating a reset pulse based on an output signal of the second voltage detection circuit, The external device and the switching circuit for switching and controlling the power supply from the battery control the memory unit via the memory control unit with a reset pulse, and the data in the memory unit due to noise when the power supply voltage fluctuates. Can be prevented from being destroyed.

Further, in the above invention, the battery voltage detector detects the voltage of the battery only when the power of the external device is switched from the off state to the on state, and sends the detection result to the external device via the connection unit. And the output circuit holds the detection result until the power supply of the external device is turned off again, so that when the external device is on, the unnecessary voltage of the battery which is not consumed is not consumed. The detection can be prevented, and the external device can always use the detection result to determine whether the data stored in the memory unit is valid or invalid, and whether new data can be stored.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a connection unit, which receives power from the external device 2 and transmits and receives signals. Reference numeral 3 denotes a memory unit composed of a memory LSI, which includes at least one static RAM or dynamic RAM, which is a volatile memory for reading and writing data from the external device 2 via the connection unit 1. Reference numeral 4 denotes a battery, which is a backup power supply that retains the contents stored in the volatile memory of the memory unit 3 when power is not supplied from the external device 2 via the connection unit 1. Reference numeral 5 denotes a power supply control unit, which controls a power supply source for holding the stored contents of the memory unit 3.
Control is performed by switching from the external device 2 to the battery 4 or from the battery 4 to the external device 2. Reference numeral 6 denotes a memory control unit which receives a signal from the external device 2 via the connection unit 1 and
Control. Reference numeral 7 denotes a battery voltage detection unit that detects a terminal voltage of the battery 4. The detection result is sent to the external device 2 via the connection unit 1. The external device 2 receives this information, grasps the state of the battery 4, and outputs each signal for protecting the storage contents of the IC memory card.

The battery voltage detecting section 7 includes a voltage dividing circuit 11, a switch circuit 12 for supplying a terminal voltage of the battery 4 to the voltage dividing circuit 11, and a first voltage detecting circuit for detecting an output voltage of the voltage dividing circuit 11. 13, and an output circuit 14 that receives an output signal of the first voltage detection circuit 13 and supplies the output signal to the connection unit 1. The switch circuit 12 is operated by a signal from the power supply control unit 5.

On the other hand, the power supply control unit 5 includes a second voltage detection circuit 8 for detecting a power supply voltage from the external device 2, a pulse circuit 9 for generating a reset pulse based on an output signal of the second voltage detection circuit 8, It comprises a switching circuit 10 for switching and controlling the power supply from the external device 2 and the battery 4 in accordance with the output signal of the second voltage detection circuit 8.

In FIG. 2, 1 which constitutes a voltage dividing circuit 11
1A and 11B are resistors, and 12 is a switch circuit. In the present embodiment, the switch circuit 12 has F
Although ET is used, other switching elements may be used.

In FIG. 3, 13A is a reference voltage generator, 13B, 13C and 13D are resistors, and 13E
And 13F are voltage comparators. Voltage comparators 13E and 13
When both the output signals of F are at the high level, a signal indicating that the terminal voltage of the battery 4 is within the normal range and the data of the memory unit 3 is stored and held is output to the connection unit 1. In response to this signal, the external device 2 informs the user that the battery voltage is normal. When only the output signal of the voltage comparator 13E becomes low level, the terminal voltage of the battery 4 has decreased, indicating that the battery 4 needs to be replaced or charged. At this time, the memory unit 3 is still stored and held by the battery 4, and this information is also transmitted from the external device 2 to the user in the same manner as in the normal state. Voltage comparator 1
When the output signals of 3E and 13F both become low level, the terminal voltage of the battery 4 further decreases, and it is necessary to replace or charge the battery 4 and that the data of the memory unit 3 has not been stored and held. The indicated signal is transmitted from the external device 2 to the user.

The protection operation of the IC memory card of the present invention configured as described above will be described.

First, an IC is connected to the external device 2 through the connection unit 1.
When the power of the external device 2 is turned on with the memory card connected, the IC memory card receives power supply from the external device 2. The power supply controller 5 detects the power supply voltage supplied from the external device 2 by the second voltage detection circuit 8 and generates a reset pulse by the pulse circuit 9 based on the output signal of the second voltage detection circuit 8. This reset pulse is applied to the switch circuit 1
2 is operated, the terminal voltage of the battery 4 is divided by the voltage dividing circuit 11 and supplied to the first voltage detecting circuit 13. The output circuit 14 receives the output signal of the first voltage detection circuit 13 and supplies the signal to the connection unit 1. As a result, the external device 2 can know the result of measuring the terminal voltage of the battery 4 via the connection unit 1, and outputs each signal for protecting the storage contents of the IC memory card based on the result. .

According to this configuration, as shown in FIG. 3, the voltage detecting circuit 13 does not need to be provided with a resistor corresponding to 21E of the conventional example (FIG. 5), so that unnecessary power consumption can be eliminated in the voltage detecting circuit 13. The life of the battery 4 can be extended several times.

At the time of checking the terminal voltage of the battery 4,
Since the resistor 11B of the voltage dividing circuit 11 is connected to the input of the first voltage detecting circuit 13, the input terminals of the voltage comparators 13F and 13G are not connected when the battery 4, which is a problem of the conventional example, is not mounted. When the voltage comparators 13F and 13F are opened, a malfunction occurs due to the influence of the input bias current and the influence of noise caused by opening the high impedance input.
It is determined that the terminal voltage of the battery 4 is normal in the external device 2 and the memory unit 3 is stored and held even though the output signal of G becomes high level and the battery 4 is not mounted. There is no disadvantage of getting it.

At this time, when the power supply control unit 5 is not connected to the external device 2, the switching circuit 10 switches the power supply source to the memory unit 3 to the battery 4 and stores the data in the memory unit 3. The content has been kept smoothly. In addition, when the external device 2 is turned on or off,
A reset pulse is generated by a pulse circuit 9 by a second voltage detection circuit 8 monitoring a power supply voltage from the external device 2, and the memory unit 3 is controlled by a signal based on the reset pulse to increase or decrease the power supply voltage. Of the memory section 3 is prevented from being destroyed due to noise during the transition period.

Next, the check of the terminal voltage of the built-in battery 4 will be described. When the connection unit 1 is connected to the external device 2, power is supplied from the external device 2 and the battery 4
Battery is not exhausted because power is not supplied from
It does not make sense to periodically and repeatedly measure the terminal voltage of the battery 4. When not connected to the external device 2 or when the power of the external device 2 is turned off and the power is not supplied from the external device 2, the power is supplied from the battery 4 and the battery 4 is being consumed. Therefore, the terminal voltage of the built-in battery 4 is checked only when the connection unit 1 is connected to the external device 2 and the power is newly supplied from the external device 2. Is generated and the switch circuit 12 is turned off, so that the battery 4 is connected while the connection unit 1 is connected to the external device 2.
Since the terminal voltage check is not performed, power saving of the battery 4 can be achieved.

The result of checking the terminal voltage of the battery 4 is maintained by the output circuit 14 unless the power of the external device 2 is turned off. It can be determined whether or not the storage content of the unit 3 is valid. Then, it can be similarly determined whether new data can be stored or not.

When the power is supplied from the battery 4, the battery 4 is depleted, and it is needless to say that the terminal voltage of the battery 4 needs to be checked as in the conventional case.

[0027]

As described above, according to the present invention, it is not necessary to provide a resistor equivalent to 21E of the conventional example for preventing the input terminal from being opened in the voltage detection circuit. In addition, since the resistor provided in the voltage dividing circuit is provided even when the battery is not mounted, it is possible to prevent the voltage detecting circuit from being opened. This makes it possible to provide an IC memory card which can extend the life of the battery without malfunction of the voltage detection circuit.

Further, by controlling the memory unit with a signal based on a reset pulse generated from a pulse circuit, it is possible to provide an IC memory card which can prevent the storage contents of the memory unit from being destroyed due to noise such as a change in power supply voltage.

Further, if the battery voltage detection unit detects the battery voltage only when the power of the external device is newly turned on, and the detection result is provided to the external device via the connection unit, it becomes unnecessary. An IC memory card that can prevent detection and allows an external device to use the detection result to determine whether the storage content of the memory unit is valid or invalid, and whether or not new data can be stored. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of an IC memory card according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a voltage divider / switch according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a first voltage detection circuit according to an embodiment of the present invention;

FIG. 4 is a block diagram showing a conventional IC memory card.

FIG. 5 is a main part circuit diagram of a conventional IC memory card.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 connection unit 2 external device 3 memory unit 4 battery 5 power control unit 6 memory control unit 7 battery voltage detection unit 8 second voltage detection circuit 9 pulse circuit 10 switching circuit 11 voltage division circuit 12 switch circuit 13 first voltage detection Circuit 14 Output circuit

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G06F 12/16 340 G06K 17/00 E G06K 17/00 G06F 1/00 330E 333D 335C

Claims (3)

[Claims] An IC memory card to which an external device is connected and which performs a memory holding operation, a connection portion receiving power from the external device and transmitting / receiving a signal, and a memory including at least one volatile memory Unit, a memory control unit that controls the memory unit according to a signal from the external device, a battery that stores and holds volatile memory in the memory unit, and controls switching between power supply from the external device and the battery. A power supply control unit; and a battery voltage detection unit that detects a terminal voltage of the battery, wherein the battery voltage detection unit includes a voltage dividing circuit, a switch circuit that supplies a terminal voltage of the battery to the voltage dividing circuit, A first voltage detection circuit that detects an output voltage of the voltage circuit, and an output circuit that receives an output signal of the first voltage detection circuit and supplies a signal to the connection unit. That I
C memory card. 2. A power supply control unit comprising: a second voltage detection circuit for detecting a power supply voltage supplied from an external device; a pulse circuit for generating a reset pulse based on an output signal of the second voltage detection circuit; 2. The IC memory card according to claim 1, further comprising a switching circuit for switching and controlling power supply from a battery. 3. The battery voltage detector detects the voltage of the battery only when the power of the external device is switched from an off state to an on state, and sends a detection result to the external device via a connection unit. 3. The IC memory card according to claim 1, wherein the output circuit holds the detection result until the power supply of the external device is turned off again.