ICL7665SCBAZ datasheet(10/15 Pages) RENESAS

10 / 15 page

ICL7665S

FN3182 Rev 10.00

Page 10 of 15

August 10, 2015

Combination Low Battery Warning and Low

Battery Disconnect

When using rechargeable batteries in a system, it is

important to keep the batteries from being over discharged.

The circuit shown in Figure 14 provides a low battery

warning and also disconnects the low battery from the rest of

the system to prevent damage to the battery. The OUT1 is

used to shutdown the ICL7663S when the battery voltage

drops to the value where the load should be disconnected.

As long as VSET1 is greater than 1.3V, OUT1 is low, but

when VSET1 drops below 1.3V, OUT1 goes high shutting off

the ICL7663S. The OUT2 is used for low battery warning.

When VSET2 is greater than 1.3V, OUT2 is high and the low

battery warning is on. When VSET2 drops below 1.3V, OUT2

is low and the low battery warning goes off. The trip voltage

for low battery warning can be set higher than the trip

voltage for shutdown to give advance low battery warning

before the battery is disconnected.

Power Fail Warning and Power-up/Power-down

Reset

Figure 14 shows a power fail warning circuit with

power-up/power-down reset. When the unregulated DC

input is above the trip point, OUT1 is low. When the DC input

drops below the trip point, OUT1 shuts OFF and the power

fail warning goes high. The voltage on the input of the 7805

will continue to provide 5V out at 1A until VIN is less than

7.3V, this circuit will provide a certain amount of warning

before the 5V output begins to drop.

The ICL7665S OUT2 is used to prevent a microprocessor

from writing spurious data to a CMOS battery backup

memory by causing OUT2 to go low when the 7805 5V

output drops below the ICL7665S trip point.

FIGURE 13. MULTIPLE SUPPLY FAULT MONITOR

HYST1

VSET1

VSET2

HYST2

V+

OUT1

OUT2

274k



R21

100k



POWER

301

R11

+5V

-15V

-5V



787



+5V



1.02M



R21A

R21B

49.9k



+5V

+15V

HYST1

SET1

SET2

HYST2

V+

OUT1

OUT2

R31

R32

R12

R11

R21

R22

GND

LOW BATTERY SHUTDOWN



V+

OUT1

SHUTDOWN

VSET

OUT2

V+

GND



LOW BATTERY WARNING

SENSE

100



+5V

ICL7663S

ICL7665S

FIGURE 14. LOW BATTERY WARNING AND LOW BATTERY DISCONNECT

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