JP2890302B2 - Electronic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device, and more particularly, to an improvement in a memory card electronic device.

[0002]

2. Description of the Related Art The voltage of a backup battery is detected in order to know when to replace a memory backup battery in a memory card (or whether replacement is necessary or not). As a detection method, a part of the battery terminal can be contacted from the outside, and the terminal voltage is measured by a tester or the like, or a voltage detection circuit having a comparator or the like is provided inside for detection. Can be raised. The important detection method in these cases is that the capacity of the backup battery must not be consumed for voltage detection, and when the voltage is detected by the voltage detection circuit, the power is not supplied to the “OFF” state. There must be no path at which the backup battery discharges at one time, and so on.

[0003]

However, when a memory card or the like is provided with a detection external terminal for detecting the voltage of the backup battery, it may be dropped to ground (GND) when it is exposed. There is a disadvantage that an accident that the battery is discharged and power is consumed easily occurs. Further, in the method of providing a voltage detection circuit such as a comparator inside and detecting the voltage of the backup battery, extra power is required to operate the voltage detection circuit.
Even when the card is in an operating state as in the case of the card-shaped storage device of -39520, the current from the battery is applied to the voltage detection circuit and the power is consumed even when the voltage detection is unnecessary. Power consumption is a problem. The present invention is to solve such a problem of the related art, and to provide an electronic device capable of suppressing unnecessary power consumption by a voltage detection circuit and reducing a power load on a backup battery. With the goal.

[0004]

According to a first aspect of the invention, there is provided an electronic apparatus having a memory backed up by a battery, and a power supply to the memory backed up by the battery. A voltage comparison circuit having a current outflow type input terminal connected to the supply line or the positive electrode connection side line of the battery, a reference voltage generation circuit that generates a reference voltage according to power supplied from the outside ,
A first terminal for externally supplying power to the memory, and a voltage ratio
What is the first terminal for the comparison circuit and the reference voltage generation circuit?
A second terminal for independently supplying power from the outside is provided, and a voltage comparison circuit and a reference voltage generation circuit operate with the power supplied from the second terminal to compare the voltage of the input terminal with the reference voltage The comparison result is output to the outside, and the input terminal has a high input impedance when the voltage comparison circuit is not operating.

Another feature of the electronic device of the second invention is that the power supply is a negative power supply, the input terminal of the voltage comparison circuit is of a current inflow type, and the current flowing from the load side to the negative power supply line is in front of the battery. In this case, the flow is divided for comparison.

[0006]

As described above, the comparison terminal of the voltage comparison circuit is of a current outflow type (inflow type with a negative power supply),
The voltage comparison circuit is operated by external power, and maintains a high impedance when not in operation. Then, in the voltage detection state of the backup battery, the sum of the input current of the input terminal for voltage comparison and the current from the backup battery is caused to flow as a backup current to a target circuit such as a memory (in the case of a negative power supply, the load from the load side). The current flowing to the negative power line is divided before the battery.) In addition, a terminal for supplying power to the memory from the outside
Has an independent power supply terminal to provide a voltage comparison circuit and reference
Operate the voltage generator independently with that power
To separate these circuits from other internal circuits.
Can be. This allows the voltage comparison circuit and the reference voltage generator
The connection lines with the batteries in the raw circuit are not
When the input terminal has a high input impedance when
Wiring line. This allows backup
Leakage current at the time of shutdown can be suppressed. Moreover,
Do not apply operating current to these circuits in the operating state.
Power consumption since power supply terminals are provided independently
Can be reduced.

[0007] As a result, by having the current outflow type input terminal, even if the voltage of the battery is detected during operation, the current flowing out of the input terminal is supplied to the power supply line to the memory or the positive electrode connection side of the battery. Since the current flows from the line to the memory, the discharge of the battery during this period is suppressed, and the current at this time is small, so that the voltage of the battery in the backup state does not fluctuate.
Therefore, there is no adverse effect on the memory. As a result, wasteful power consumption of the backup battery can be suppressed at the time of battery voltage detection and at the time of backup.

[0008]

FIG. 1 is a block diagram of an embodiment in which the electronic apparatus of the present invention is applied to a memory card, FIG. 2 is a block diagram of another embodiment, and FIG. 3 is another embodiment. FIG. 3 is a block diagram of an example. In FIG. 1, reference numeral 1 denotes a memory card, which is used by being mounted on a memory card reader / writer 2 (hereinafter, reader / writer 2).

The memory card 1 includes a RAM 3 as a semiconductor memory, a backup battery 4 for holding the stored data, and a power supply for switching the power of the backup battery 4 and the power supplied from the outside to supply the power to the RAM 3. A switching circuit 5, a reference voltage generating circuit 6 for receiving a power from the outside to generate a reference voltage, and a voltage comparing circuit (COM) for comparing the reference voltage with the voltage of the backup battery 4
7 is provided. Further, the memory card 1 has two power supply terminals 8 for receiving power supplied from the outside,
9 and a voltage comparison circuit 7 for comparing the voltage of the backup battery 4 with the reference voltage and outputting the result of the determination to the outside.
, 11n... 11n connected to a bus for data and control signals to the RAM 3, and a ground (GND) terminal 12 are provided as external connector terminals. .

Here, the power supply switching circuit 5 is composed of two diodes D ₁ and D ₂ whose cathodes are commonly connected to the power supply terminal Vcc of the RAM _{3. The} power supplied from the power supply terminal 8 is supplied to the diode D _1. Via the RAM 3.
When power is not supplied from the outside via the power supply terminal 8, this circuit supplies the power from the backup battery 4 to the RAM 3 via the diode D ₂ , and supplies the power from the external power to the internal backup battery 4. The power supply is switched. The voltage comparison circuit 7 has a differential amplification type amplifier 13 composed of two PNP transistors whose emitters are connected to each other as shown in the figure. The bases of the PNP transistors are respectively (+) and (-). The (+) phase side input terminal is connected to the power supply terminal VCC of the RAM 3, and the (−) phase side input terminal is connected to the output of the reference voltage generating circuit 6. Note that the reference voltage generation circuit 6 and the voltage comparison circuit 7 operate by receiving external power supplied from the power supply terminal 9.

Next, the operation will be described. When the memory card 1 is mounted on the reader / writer 2, the reader / writer 2 first applies a voltage + from the power supply circuit to the power supply terminal 9.
Supply 5V power. At this time, no electric power is supplied to the power supply terminal 8 side. Then, first, the reference voltage generation circuit 6 and the voltage comparison circuit 7 operate, and the reference voltage generation circuit 6 generates Vref (reference voltage), and sends this to the (−) phase input terminal side of the voltage comparison circuit 7. Is sent. In this state, since no voltage is supplied to the power supply terminal 8, the output voltage of the power supply switching circuit 5, that is, the power supply voltage Vcc of the RAM 3 is a voltage backed up by the backup battery 4. Then, the signal of this voltage (Vcc) becomes an input on the (+) phase input terminal side of the voltage comparison circuit 7, and the voltage Vcc from the backup battery 4 and the voltage of Vref are compared by the voltage comparison circuit 7, and as a result, Is output to the determination result output terminal 10.

[0012] The reduction in comparison subject to voltage, the voltage of the backup battery 4 by comparing the Vcc from being a voltage obtained by subtracting the forward voltage of the diode D ₂ from the voltage Va of the backup battery 4 Va at this time You can know. Therefore, it is now assumed that Vref is 0.2 V higher than the minimum voltage (2.0 V) required for holding data in the RAM 3.
V, and the voltage comparison circuit 7 outputs (+)
When the voltage of the phase input terminal is higher than the voltage of the (−) phase input terminal, an output of a HIGH level (hereinafter “H”) is generated, and in the opposite case, an output of a LOW level (hereinafter “L”) is generated. Shall occur.

When the backup battery 4 generates a predetermined voltage and the comparison target voltage Vcc is 2.2 V or more, an output of "H" is obtained at the judgment result output terminal 10. Conversely, when the comparison target voltage Vcc decreases due to the discharge of the backup battery 4 and becomes 2.2 V or less, an output of "L" is obtained at the determination result output terminal 10. The reader / writer 2 obtains the output level of the determination result output terminal 10 as an output signal from the determination result terminal 10 when the memory card 1 is inserted, and detects the state of the backup battery 4 by determining this. And then, the leader
The writer 2 detects whether battery replacement is necessary.

Here, the comparison operation of the voltage comparison circuit 7 is as follows.
Amplifier of Differential Amplification Type Using Two PNP Transistors 1
3 and RA is connected to the base of the PNP transistor.
Since the power supply terminal Vcc of M3 is connected, the base current of the PNP transistor flows out to the input terminal of the voltage comparison circuit 7. Therefore, when the voltage of the backup battery 4 is compared, the sum of the base current and the current from the backup battery 4 is equal to the RAM.
3 is a current for backup. Since this base current direction is opposite to the direction in which the backup battery 4 is discharged, in the state where the voltage of the backup battery 4 is detected, the backup battery 4
Unnecessary discharge is not performed. Further, the current flowing out of the (+) phase input terminal of the voltage comparison circuit 7 can be set extremely small with respect to the amount of current required for the backup of the RAM 3. Has little effect.

Further, when not mounted on the reader / writer 2, that is, in the backup state, the relationship between the voltage comparison circuit 7, the reference voltage generation circuit 6, and the backup battery 4 is simply the PNP type of the voltage comparison circuit 7. Since only the power supply terminal VCC of the RAM 3 is connected to the base of the transistor and the input impedance from the base side to the collector side is very high, the power consumed is extremely small and almost no power is consumed. State can be suppressed. By the way, when the reader / writer 2 determines the signal from the output from the determination result output terminal 10 and detects the voltage of the backup battery 4 when the memory card 1 is inserted, the determination output is “H”. For example, it is not time to replace the battery, and it is determined that data transmission / reception is possible (OK), and power of +5 V is supplied to the power supply terminal 8. Then, the backup by the backup battery 4 is stopped, and the process of data transfer with the RAM 3 via the terminals 11 ₁ ,.

In this data transfer stage, the reader / writer 2 ignores the state of the determination result output terminal 10 and executes predetermined data processing. In addition, leader ・
Writer 2 detects voltage of backup battery 4 and OK
, The reader / writer 2 may perform processing so as to stop the power supply at the power supply terminal 9 at that time. When the memory card 1 is ejected or removed from the reader / writer 2, the power supply terminal 9 may be short-circuited to GND in some cases. Is a PNP transistor, so that the input impedance is high, so that unnecessary discharge of the backup battery 4 does not occur.

FIG. 2 shows another embodiment in which the (+) phase input terminal of the voltage comparison circuit 7 of FIG. 1 is directly connected to the backup battery 4. In this case, the backup battery 4
+ 5V to power supply terminal 9 when backing up AM3
Is supplied, the voltage of the backup battery 4 is compared with the reference voltage Vref, and the quality of the backup battery 4 is determined. This circuit is similar to the embodiment of FIG.
Since the base current flows from the (+) phase input terminal of FIG.
The mode for charging the backup battery 4 is set. Therefore,
In order to prevent such a situation, in the circuit of FIG. 2, after completing the voltage comparison, the reader / writer 2 turns off the power supply of the power supply terminal 9 and supplies the power supply terminal 8 with the power of + 5V. Is performed to switch the power supply so as to supply the power.

In the above description, the power supply is set to +5 V and a positive power supply voltage is applied to operate the RAM 3. However, when a negative power supply is applied, as shown in FIG. Amplifier 13 from the PNP transistor to N
What is necessary is just to make it the differential amplification type amplifier 13a which consists of a PN transistor. FIG. 3 shows that the input stage of the voltage comparison circuit 7a is NP
An N-type transistor is used to operate with a negative power supply. In this case, the current for backing up the RAM 3a is GN which is on the ground side.
D is supplied from the D terminal 12 to the RAM 3a, which is a load.
The current flowing out of the AM 3a is divided into the backup battery 4a and the voltage comparison circuit 7a. Therefore, the voltage comparison circuit 7
The current flowing through a does not need to be supplied from the backup battery 4.

Therefore, the backup battery 4a is not discharged by the current flowing from the (+) phase input terminal of the voltage comparison circuit 7a. Figure 3 shows a negative power reader
This is a case where the memory card 1a is mounted on an electronic device such as a writer. In this case, the voltage of the power supplied to the power terminals 8a and 9a is -5V. The sequence of power supply from the reader / writer is the same as that of the embodiment of FIG. 1. First, power is supplied to the power supply terminal 9a from a -5V power supply, and an output signal is received from the determination result output terminal 10a. The backup battery 4a is inspected by the
When it is K, thereafter, the supply of -5V power to the power supply terminal 8a is started.

By the way, in the above embodiment, when the judgment result output of the judgment result output terminals 10 and 10a detecting the voltages of the backup batteries 4 and 4a becomes "L" and indicates the battery replacement state, 4,4
The power of a is in a consumption state. Therefore, reader / writer 2
Does not exchange data with the memory cards 1 and 1a and displays a message instructing battery replacement on the display device, or ejects and discharges the memory cards 1 and 1a. As described above, when the generated voltage of the backup battery is detected at the time of backup, the input bias current of the detection voltage comparison circuit does not flow in the direction of discharging the backup battery but flows into the memory (negative). Since the power supply is configured to shunt the current flowing from the memory), unnecessary discharge of the backup battery can be almost suppressed. Also, in the backup state, only power consumption required for backup is sufficient.

As described above, in the embodiment, the signal for detecting the time of replacement of the backup battery is obtained from the determination result output terminal. However, the present invention is not limited to this. In this case, the state of various backup batteries including the state of exhaustion of the battery can be detected. Either "H" or "L" of the determination result signal may be a signal indicating the time of battery replacement, and the power supply voltage is not limited to 5V. Further, in the embodiments, the present invention has been described centering on a memory card. However, the present invention relates to various devices having a memory that needs to be backed up by a battery, such as an IC card and a memory cartridge, and further, other devices. The present invention can be applied to various electronic devices that are backed up by a battery. In the embodiment, an example is described in which a PNP transistor and an NPN transistor are used in the input stage of the voltage comparison circuit. However, these may be bipolar transistors, MOS transistors, or other similar semiconductor circuits. Good.

[0022]

As described above, according to the present invention, the comparison terminal of the voltage comparison circuit is of a current outflow type (inflow type for a negative power supply), the voltage comparison circuit is operated by external power, and Maintain high impedance when not in operation. In addition, external power is stored in memory
Provide a power supply terminal independent of the supply terminal and compare the voltage
Circuit and the reference voltage generation circuit operate independently with that power.
I am trying to. Then, in the voltage detection state of the backup battery, the sum of the input current of the input terminal for voltage comparison and the current from the backup battery is caused to flow as a backup current to a target circuit such as a memory (in the case of a negative power supply, the load from the load side). By dividing the current flowing in the negative power line before the battery), even when the battery voltage is detected,
Further, even at the time of backup, useless power consumption of the backup battery can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment in which an electronic device of the present invention is applied to a memory card.

FIG. 2 is a block diagram of another embodiment.

FIG. 3 is a block diagram of still another embodiment.

[Explanation of symbols]

1, 1a: memory card, 2: memory card reader / writer, 3, 3a: RAM, 4, 4a: backup battery, 5, 5a: power supply switching circuit, 6, 6a: reference voltage generation circuit, 7, 7a: voltage Comparison circuit, 8, 8a, 9, 9a ...
Power supply terminal, 10, 10a ... judgment result output terminal, 11, 1
1a: RAM data / control terminal group, 12, 12a ...
Ground (GND) terminal.

────────────────────────────────────────────────── (5) Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI H02J 7/00 G06K 19/00 J (56) References JP-A-2-30599 (JP, A) JP-A-62-241016 ( JP, A) JP-A-57-173220 (JP, A) JP-A-58-154672 (JP, A) Actually open Showa 64-39520 (JP, U) Actually open Showa 63-92976 (JP, U) Actually open Showa 60-53065 (JP, U) Actually open Showa 58-134774 (JP, U) Actually open Showa 61-178479 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01R 19 / 00-19/32 G01R 31/36 B42D 15/10 G06F 1/28 G06K 19/07-19/077 H02J 7/00

Claims (3)

(57) [Claims] 1. An apparatus having a memory backed up by a battery.
An electronic device that includes a voltage comparator circuit having an input terminal of the positive electrode connecting end connected current outflow type to the line of the power supply line or the battery to the memory that is backed up by the battery, depending on the power supplied from the outside a reference voltage generating circuit for generating a reference voltage Te, or external to the memory
A first terminal for supplying power from the
The first terminal for the reference voltage generating circuit
A second terminal for supplying power from the outside , and wherein the voltage comparison circuit and the reference voltage generation circuit operate with the power supplied from the second terminal to operate the voltage of the input terminal. And outputs the comparison result to the outside by comparing with the reference voltage,
The electronic device, wherein the input terminal has a high input impedance when the voltage comparison circuit is not operating. 2. An electronic device having a memory which is backed up by a battery having a negative voltage output with the ground side being a positive side, wherein a negative power supply line to the memory which is backed up by the battery or a negative connection side line of the battery. A voltage comparison circuit having a current inflow type input terminal connected to a reference voltage generation circuit that generates a reference voltage according to power supplied from the outside, and a current flowing out of the memory.
The negative voltage output from the outside to flow to the outside
1 terminal, the voltage comparison circuit and the reference voltage generation
The circuit has the negative terminal independent of the first terminal.
And a second terminal for outputting a voltage of the reference voltage , wherein the voltage comparison circuit and the reference voltage generation circuit are supplied from the ground side.
Operating by the power flowing out through the second terminal, comparing the voltage of the input terminal with the reference voltage, and outputting a comparison result to the outside, and the input terminal is not operating the voltage comparison circuit. An electronic device characterized by sometimes having a high input impedance. 3. The electronic device is a memory card or an IC card, and the reference voltage is a voltage set for detecting whether or not the battery needs to be replaced.
An electronic device as described.