HT70XX

Rev. 1.60

8

January 14, 2003

5V power line monitoring circuit

Generally, a minimum operating voltage of 4.5V is guar-

anteed in a 5V power line system. The HT7044A is rec-

ommended for use as 5V power line monitoring circuit.

Change of detectable voltage

If the required voltage is not found in the standard prod-

uct selection table, it is possible to change it by using ex-

ternal resistance dividers or diodes.

vider

Detectable voltage =

RR

R

AB

B

+

Hysteresis width =

RR

R

AB

B

+

Malfunction analysis

The following circuit demonstrates the way a circuit ana-

lyzes malfunctions by monitoring the variation or spike

noise of power supply voltage.

Charge monitoring circuit

The following circuit shows a charged monitor for pro-

tection against battery deterioration by overcharging.

When the voltage of the battery is higher than the set de-

tectable voltage, the transistor turns on to bypass the

charge current, protecting the battery from overcharg-

ing.

H T 7 0 X X A

H T 7 0 X X A

V f 1

V f 2

H T 7 0 4 4 A

C

5 V P o w e r l i n e

D

R

H T 7 0 4 4 A

H T 7 1 5 0

G N D

5 V

5 V V o l t a g e r e g u l a t o r

H T 7 0 X X A

H T 7 0 X X A

L o a d

B A T T

S o l a r

C e l l

T r