JPH02222048A - Information storage medium - Google Patents

Abstract

PURPOSE:To reduce the stand-by current and to increase the lifetime of a built-in power supply by detecting a volatile memory storing data and supplying the electricity of a power supply for data holding to the volatile memory only. CONSTITUTION:The write control data are fetched to the nonvolatile memories IC 131 and 132 from a control IC 12. Thus a switching IC 16 detects the memories 131 and 132 storing data and controls a switch. As a result, the data holding power is supplied to only both memories 131 and 132 storing data from a built-in power supply IC 14. Then the stand-by current is reduced and the lifetime of a built-in power supply is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an information storage medium in which a card-like medium has a built-in memory for storing information.

(Prior Art) Memory cards, in which a card-like medium has a built-in memory IC for storing information, have been becoming popular as portable information storage media. How much information a memory card can store, that is, the size of the memory capacity, determines the quality of the product, and in the future, a large number of memory ICs will be implemented in a card medium of limited size. There is a tendency.

As shown in FIG. 4, a conventional memory card has a connector 11 for connecting to a card storage/reader main body (not shown), and information data, read/write control data, Take in the power supply voltage and control information data and control data
and supplies power input to the power supply IC 14.

When the read/write control data instructs writing, the control IC 14 transfers the manual data to memory ICs 132 connected in parallel according to the instruction.
,... When writing or reading is instructed by selecting one of the following, the memory IC 13 is written according to the instruction.
1, 132, . . . to read predetermined information data and send it to the main body through the connector 11. On the other hand, when the power supply IC 14 is supplied with the power supply voltage E from the main body, the power supply voltage is distributed and supplied to the control IC 12 and the memory ICs 131, 132, etc. to execute the above read/write operation. When the card is separated from the main body, the power output from the backup power supply 15 built into the card is supplied to each IC 12, 131, 132, etc., and the stored data is retained. .

That is, assuming that the memory card with the above configuration is of a rewritable type, the memory IC 131,1 to be used is
32, . . . use volatile memory such as DRAM or SRAM, and usually the output of a backup power supply 15 built into the card, such as an ultra-thin button-type lithium battery, is connected to each IC 12, Hl, 132,・
Each IC12, 131 retains the data supplied and stored in the main unit, and outputs power from the main unit only when connected to the main unit.
, 132, . . . to read and write data. However, if electrically recordable/erasable non-volatile memory such as EEFROM is used, backup power supply 1 is required.
5 becomes unnecessary, but since there is currently no large-capacity EEPROM, it is not suitable for use in, for example, a memory card for an electronic still camera that needs to store a large amount of image information.

Here, a major problem when using a memory card with the above configuration is the lifespan of the backup power source for data retention when the card is not in use. For example, assuming a memory card with a memory capacity of 20 Mbits, that is, a memory card equipped with 20 IM bit DRAM memory ICs, the data retention current (standby current) Iss per memory IC is approximately 2
00 [μA], and if the circuit shown in Figure 4 is used, ISB will be supplied to all the built-in memory ICs, so 2
00 [μA] X20=4 [mA]. If a lithium battery with a battery capacity of 125 [mAh] is used as a backup power source, the battery life will be approximately 30 mAh.
It will take about an hour. That is, in order to avoid erasing stored data, it is necessary to replace the battery within 30 hours, and frequent battery replacement is extremely inconvenient as a product.

(Problems to be Solved by the Invention) As described above, conventional information storage media, particularly memory cards, place a heavy burden on the backup power source for data retention and require frequent battery replacement, which impairs practicality.

This invention was made in order to solve the above-mentioned problems, and provides an information storage medium that can reduce the standby current required for data retention, extend the life of the built-in power supply, and reduce the need for replacement. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, an information storage medium according to the present invention includes a plurality of volatile memories and a power supply for retaining their data, and includes the above-mentioned The device includes means for detecting a memory that stores data among the volatile memories, and means for supplying the output of the data holding power source only to the memory detected by this means.

(Function) In the information storage medium having the above configuration, power output is supplied only to the memory that stores data, so the standby current can be reduced and the life of the built-in power supply can be extended.

(Example) The present invention will be described in detail below with reference to FIGS. 1 to 3. However, in FIGS. 1 to 3, the same parts as in FIG. 4 are denoted by the same reference numerals, and only the different parts will be described here.

FIG. 1 shows the configuration of a first embodiment of a memory card according to the present invention, in which a switching IC 1B is newly added to the card. This switching IC 1ft takes in write control data from the control IC 12 and transfers it to each memory IC 131, 132,
. . , and selectively supplies the power output from the power supply IC 14 only to the memory IC in which the data is stored.

For example, when data is stored only in the memory IC 131, write control data is output from the control IC 12 only to the memory IC 131. Switching IC
1B takes in the write control data to the memory IC 131 and switches its internal circuit so that the power supply voltage is supplied only to the memory IC 131. If it is disconnected from the main body in this state, it will be used for switching! 016 maintains its connection state, the standby current ISB is
It will be supplied only to 1B.

Assuming an example of a memory card in which 20 memory ICs of the IM bit DRAM described above are mounted, in the above example, 138 is supplied only to the memory IC 131.
If the data retention current (standby current) Iss per memory IC is approximately 200 [μA], the entire standby current ISO is 200 [, czA] Xl-2
00 [μA], and the conventional total standby current is 1 s,
The current consumption is much lower than -4 [mA]. Therefore, the life of the battery will be approximately 20 times longer than that of conventional batteries. Incidentally, since the added switching IC 16 can be a commonly used one with a low current consumption of about 10 μA, the current consumption of the entire card is negligible. Further, the standby currents of the control IC 12 and the power supply IC 14 are each about 100 μA and 150 μA, which is extremely small compared to the total of 158 μA, and there is no problem in practical use.

Therefore, as long as the number of memory ICs storing data is small, the memory card with the above configuration can keep the standby current extremely low, extending the life of the battery, and making it possible to replace the battery with an open type. This eliminates the need to do so, making it extremely practical.

FIG. 2 shows a second embodiment of the memory card according to the present invention, in which each memory IC 131, 132, .
...is configured with a power input switching function. That is, each memory IC 131, 132, . . .
each selects whether or not to supply power to its own IC chip cell from the control IC 12 according to control data, and when selecting power supply, closes the power input terminal P1n and receives the power output from the power IC 14. , write, read, and hold data.

According to this configuration, as in the case of FIG. 1, the standby current ISO is supplied only to the memory IC that stores data. When each memory IC is provided with a switching function, its ISB is about 0.5 μA, so current consumption can be reduced and battery life can be extended. In particular, according to this configuration, there is no need to provide a dedicated power supply line for each memory IC as in the configuration shown in Figure 1, and the power supply line can be shared, so the circuit size can be kept almost to the conventional level. It has the advantage of being able to

FIG. 3 shows a third embodiment of the memory card according to the present invention, in which the switching IC 1 [
It is constructed by incorporating a functional SW equivalent to i into the control 1c12. The operation is the same as that shown in FIG. 1, so it will not be described here, but the increase in current consumption of the control IC when the switching function is incorporated in this way is considered to be about 20μ8. Therefore, even in this configuration, the effect of extending the life of the battery is almost the same as in the other embodiments, and furthermore, since there is no need to newly provide a switching IC, it is possible to contribute to miniaturization.

In addition, in the above embodiment, a memory card was explained, but
It goes without saying that the present invention can be implemented in the same manner and the same effects can be obtained with other information storage media that use a backup power source.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an information storage medium that can reduce the standby current required for data retention, extend the life of the built-in power supply, and reduce the frequency of replacement. can.

[Brief explanation of the drawing]

1 to 3 are internal configuration diagrams showing first to third embodiments of the information storage medium according to the present invention, and FIG. 4 is a diagram showing the internal configuration of a conventional memory card. 11... Connector, 12... Control IC,
131゜132...Memory TO, 14...Power supply I
C, 15... ノ(・Power supply for pull-up, 1B... Switching IC.

Claims (3)

[Claims] (1) In an information storage medium that includes a plurality of volatile memories and a power supply for retaining these data, a data storage memory detection means for detecting a memory that stores data among the volatile memories; an information storage medium comprising power supply selection means for supplying the output of the data holding power source only to the memory in which the data is stored. (2) Claim (1) characterized in that the data storage memory detecting means performs identification from control data to the memory.
) information storage medium. (3) The information storage medium according to claim (1), wherein the data storage memory detection means and the power supply selection means are individually provided in the memory.