HT7027A データシートの表示（PDF） - Holtek Semiconductor

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HT7027A

Voltage Detector

Holtek Semiconductor 

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.

· 5V power line monitor with power-on reset

5 V P o w e r lin e

R

D

C

V SS

V DD

V OUT

H T7044A

V SS

· with 5V voltage regulator

5 V V o lta g e r e g u la to r

5V

V IN

H T7150

GND

V DD

V OUT

H T7044A

V SS

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.

· Varying the detectable voltage with a resistance di-

vider

V IN

RA

RB

V SS

V DD

V OUT

H T70X X A

V SS

HT70XX

· Varying the detectable voltage with a diode

V IN

V f1

V f2

V DD

V OUT

H T70X X A

V SS

V SS

Detectable Voltage = Vf1+Vf2+VDET

Malfunction analysis

The following circuit demonstrates the way a circuit ana-

lyzes malfunctions by monitoring the variation or spike

noise of power supply voltage.

V DD

V OUT

H T70X X A

V SS

V SS

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.

S o la r

C e ll

Tr

V DD

V OUT

BATT

Load

H T70X X A

V SS

Detectable

voltage

=

RA + RB

RB

´

VDET

Hysteresis

width

=

RA + RB

RB

´

VHYS

Rev. 1.60

8

January 14, 2003

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