HT7044A Просмотр технического описания (PDF) - Holtek Semiconductor

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HT7044A

Voltage Detector

Holtek Semiconductor 

The hysteresis width is:

VHYS = VDET (+) - VDET (-)

The figure demonstrates the NMOS output type with

positive output polarity (VOUT is normally open, active

low). The HT70XX series also supplies options for other

output types with active high outputs. Application cir-

cuits shown are examples of positive output polarity V R E .

(normally open, active low) unless otherwise specified.

RA

C o m p a ra to r

VB

RB

M1

RC

HT70XX

V DD

RL

VC

V OUT

MN

V SS

NMOS output voltage detector (HT70XXA)

Application Circuits

Microcomputer reset circuit

Normally a reset circuit is required to protect the micro-

computer system from malfunctions due to power line

interruptions. The following examples show how differ-

ent output configurations perform a reset function in var-

ious systems.

· NMOS open drain output application for separate

power supply

V DD1

V DD2

H T70X X A

V OUT

RESET

M ic r o -

c o m p u te r

V SS

· NMOS open drain output application with R-C delay

V DD

H T70X X A

R

V OUT

M ic r o -

c o m p u te r

C

V SS

Power-on reset circuit

With several external components, the NMOS open

drain type of the HT70XX series can be used to perform

a power-on reset function as shown:

V IN

R

D

C

V SS

V DD

V DD

V OUT

H T7044A

V OUT

V SS

t

V OUT

t

Rev. 1.60

7

January 14, 2003

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