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MITSUMI

PST532 Datasheet Preview

PST532 Datasheet

(PST5xx) Battery Backup IC

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MITSUMI
Battery Backup IC
Battery Backup IC
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1. Background of Development
Around 1985 when began the sales of IC for
microcomputer peripheral equipment and system
reset IC, a set manufacture inquired of us about IC for
control of memory. It was a good change for us to
decide a joint development of general purpose IC.
This resulted in the development of PST531 and
PST532. In 1989 they were improved into the backup
IC series dedicated to cards, games (popular-priced)
and to 1-chip microcomputers. Our IC series now
includes low current consumption type products.
2. What is Battery Backup IC?
Such IC memories as S-RAM and D-RAM all volatilize
when power supply is cut off. Usually we use
batteries not to let these data disappear and to store
them for a longer time (of the order of several years).
The battery backup IC can monitor main supply when
storing data by means of battery and the like, control
memory so that there should not arise any data
trouble in the memory, change the main supply over
to battery, and monitor the residual voltage of the
battery, to take a few examples.
3. Basic Configuration
Fig. 1 below illustrates the basic configuration of the
backup IC.
We have PST531, PST532 and MM1026 as IC of the
basic configuration.
3-1 Battery/Main Supply Changeover Circuit
1. 3.3V detect circuit ··· Main supply detection
2. Transistor switch ····· Main supply ON/OFF switch
3. Schottky diode ········ For supplying backup power
3-2 Configuration of CS (CE) Control circuit
1. 4.2V detect circuit ········ Detection of main supply
2. Output reverse circuit ··· Reverses CS signal into
CS one.
We have MM1025, MM1027 and MM1028 as the
backup IC having the following additional functions.
3-3 Detection of Residual Voltage of Battery
1. 2.70V detect circuit ··· Equivalent to yellow alarm
for residual voltage of battery
2. 2.55V detect circuit ··· Equivalent to red alarm for
residual voltage of battery
3-4 Battery Control Circuit
1. This circuit controls so that battery power should
not be supplied even if the battery is replaced
when there remains no main power supply when
replacing the battery.
4. Principli of Operation
4-1 Battery/Main Supply Changeover Circuit
The 3.3V detect circuit turns off the transistor switch
when VCC is 3.3V or less and turns it on when the
same exceeds 3.3V. The transistor ON will output the
voltage of main supply to VOUT and transistor OFF will
output the battery voltage to VOUT.
4-2 CS (CE) Control Circuit
The 4.2V voltage detect circuit makes CS signal to
--------------------
low level and CS to high level when VCC is 4.2V or
-------------------
lower, and CS to high level and CS to low level when
the same exceeds 4.2V. The CS signal level will
change over the S-RAM mode as indicated in Fig.1
below.
---------------------
When the CS signal is at low level (high level with CS
signal), that is when VCC is 4.2V or lower, then S-RAM
will enter into the backup mode and data read/write is
forbidden thus preventing data trouble.
Fig.1 Basic Configuration




MITSUMI

PST532 Datasheet Preview

PST532 Datasheet

(PST5xx) Battery Backup IC

No Preview Available !

MITSUMI
Battery Backup IC
5. Characteristics of Respective Models
5-1 MM1025
Intended for D-RAM (no refresh control circuit) and
pseudo-S-RAM
1. The power source used is Ni-Cd battery. Both main
supply and backup supply incorporate stabilized
power supplies.
2. With main power supply detect circuit built-in, it
changes over the stabilized power supply and
controls the memory by CS signal.
5-2 MM1026 and MM1080
For S-RAM
1. Ideal for games and IC cards. Applicable to
lowcost system configuration.
2. Then main power supplies the power for IC while
the lithium battery is used as backup power supply.
3. Incorporate forced main power supply/backup
supply changeover circuit by transistor switch (low
saturation realized by PNP transistor).
4. Schottky barrier diode built-in on the backup side.
5. With the main power supply detect circuit built-in,
they control SRAM through CS signal.
6. Current consumption under normal conditions :
MM1026 : 1.0mA typ.
MM1080 : 60µA typ.
Low current consumption type
7. Current consumption under backup conditions :
0.3µA typ.
Fig. 2 shows a block diagram of MM1026.
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5-3 MM1027 and MM1081
For S-RAM
1. Two battery checkers built-in. Applicable to JEIDA
Ver.4.0 specification for IC memory cards.
2. The main power supply provides power for IC,
while the backup power uses the lithium battery.
3. Built-in is the forced main power supply/backup
power changeover circuit (low saturation realized
by PNP transistor, approx. 0.2V).
4. Schottky barrier diode built-in on the backup side.
5. External transistor for output increase if connected,
output current 90mA will be increased.
6. Current consumption under normal conditions :
MM1027 : 1.7mA typ.
MM1081 : 100µA typ.
Low current consumption type
(under development)
7. Current consumption under backup conditions :
0.2µA typ.
Fig. 3 shows a block diagram of MM1027.
Fig.3 Block Diagram of MM1027
Fig.2 Block Diagram of MM1026


Part Number PST532
Description (PST5xx) Battery Backup IC
Maker MITSUMI
Total Page 4 Pages
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