ICL7665SCBAZ datasheet(11/15 Pages) RENESAS

11 / 15 page

ICL7665S

FN3182 Rev 10.00

Page 11 of 15

August 10, 2015

Simple High/Low Temperature Alarm

Figure 16 illustrates a simple high/low temperature alarm

which uses the ICL7665S with an NPN transistor. The voltage

at the top of R1 is determined by the VBE of the transistor and

the position of R1’s wiper arm. This voltage has a negative

temperature coefficient. R1 is adjusted so that VSET2 equals

1.3V when the NPN transistor’s temperature reaches the

temperature selected for the high temperature alarm. When

this occurs, OUT2 goes low. R2 is adjusted so that VSET1

equals 1.3V when the NPN transistor’s temperature reaches

the temperature selected for the low temperature alarm. When

the temperature drops below this limit, OUT1 goes low.

AC Power Fail and Brownout Detector

Figure 17 shows a circuit that detects AC undervoltage by

monitoring the secondary side of the transformer. The

capacitor, C1, is charged through R1 when OUT1 is OFF. With

a normal 100 VAC input to the transformer, OUT1 will

discharge C1 once every cycle, approximately every 16.7ms.

When the AC input voltage is reduced, OUT1 will stay OFF, so

that C1 does not discharge. When the voltage on C1 reaches

1.3V, OUT2 turns OFF and the power fail warning goes high.

The time constant, R1C1, is chosen such that it takes longer

than 16.7ms to charge C1 1.3V.

HYST1

VSET1

VSET2

HYST2

V+

OUT1

OUT2

5.86k



130k



BACKUP

BATTERY

7805

5V REGULATOR

UNREGULATED

DC INPUT



22M



2.2M



715k



RESET OR

WRITE

ENABLE

POWER

FAIL

WARNING

470

F

4700

F

ICL7665S

FIGURE 15. POWER FAIL WARNING AND POWERUP/POWERDOWN RESET

ICL7665SCBAZ Datasheet(PDF) 11 Page - Renesas Technology Corp

ICL7665SCBAZ Datasheet(HTML) 11 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Datasheet Download

Link URL