HT7612_12 datasheet(4/23 Pages) HOLTEK

4 / 23 page

HT7612/HT7612B

Rev. 1.70

July 16, 2012

Functional Description

The following gives a description of the functional pins

on the device.

TEST

The TEST pin is an output which is used to test the 32

KHz system frequency. Note that the pin is a shared

TEST/SC pin. The TEST output pin can be used within 1

second after power-on.

The SC pin is an output pin which is used to for LVD and

CDS detection. Note the pin is a shared TEST/SC pin.

The SC pin can be used 1 second after power-on.

The DT pin is a delay time oscillator input pin. It is con-

nected to an external RC to obtain the desired output

turn-on duration. Variable output turn-on durations can

be achieved by selecting various values of RC or using

a variable resistor. The DT structure is shown in Fig.1.

BUZ/BUZ

The BUZ & BUZ pins are both CMOS output structures.

They will output 4 beep sounds within 1second to indi-

cate that the warm-up time has completed. These differ-

ential output pins can be used to drive a piezo buzzer.

The BUZ/BUZ structure are shown in Fig.2.

RELAY

The RELAY pin is a CMOS output structure which is nor-

mally low and active high. The high duration is con-

trolled by the delay time oscillator and the MODE pin.

The RELAY pin structure is shown in Fig.3.

TRIAC

The TRIAC pin is a CMOS output structure which will

output a series of pulses when active. The pulse train is

synchronised by the ZC (zero crossing) input. The ac-

tive duration is controlled by the delay time oscillator

and the MODE pin. The TRIAC structure is shown in

Fig.4.

V R E F

D T

S R

F F I

C o m p

O s c i l l a t o r

C L K

Fig.1 DT Oscillator Structure

B U Z / L V D

B U Z / C D S

Fig.2 Buzzer Pin Drive Buzzer

V D D

R E L A Y / L E D

1 0 k W

L O A D

A C

R E L A Y

8 0 5 0

Fig.3 RELAY Pin Drive RELAY

T R I A C

1 0 k W

L O A D

A C

T R I A C

0 . 0 4 7 m F

6 8 W

Fig.4 TRIAC Pin Drive TRIAC

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