HT7612

Rev. 1.20

5

February 9, 2010

MODE

The MODE pin is a tristate input which is used to select the desired device operating mode.

MODE pin

Status

Operating

Mode

Description

VDD

ON

Output is always ON:

RELAY output high for RELAY driving.

TRIAC pulse train output is synchronised by ZC for TRIAC driving.

VSS

OFF

Output is always OFF:

RELAY output low for RELAY driving.

TRIAC output low for TRIAC driving.

OPEN

AUTO

Outputs remain in the OFF state until activated by a valid PIR input trigger signal. When

working in the AUTO mode, the devices allows for an override control by switching the ZC

signal.

The device also provides an additional test function on

the MODE pin. If the MODE pin is presented with a high

pulse, of greater than 400ms duration, within 1 second

after power-on, the device will be forced into its test

mode. When the device enters the test mode the

power-on delay time will be changed from its normal op-

erating value of 40 seconds to 10 seconds.

ZC

The ZC pin is a CMOS Schmitt trigger input pin. Using

suitable ZC signal switching, the device can provide the

following functions:

When the device is operating in the AUTO mode,

which is when the MODE pin is open, the output will

be activated by a valid PIR trigger signal and the out-

put active duration will be controlled by a DT oscillat-

ing period. The mode can be switched from the AUTO

mode to the

²ON² mode by either connecting the

MODE pin to VDD or switching the ZC signal with an

OFF/ON operation of the power switch. The term

²override² refers to the change of operating mode by

switching the power switch. The device can be tog-

gled from ON to AUTO by an override operation. If the

device is overridden to ON and there is no further

override operations, it will automatically return to the

AUTO mode after 8 hours. It will flash 3 times at a 1Hz

rate when returning to the AUTO mode. But if the

AUTO mode is changed by switching the MODE

switch, it will not flash, as shown in Fig.5.

In Fig.6, an external pull-high resistor is required for nor-

mal applications.

Note:

Regarding the priority of the MODE pin and the

ZC switching, note that when the MODE pin is

connected to VDD or VSS, the MODE state will

be determined by the MODE pin.

When the MODE pin is OPEN, the MODE state

will be determined by the ZC switching.

A U T O

O N

A U T O

O N

f l a s h

Z C

A U T O

f l a s h

A l w a y s h i g h o r a l w a y s L o w

O p e r a t i n g

M o d e

< 3 s e c

8 h r

> 3 0 m s

Fig.5 ZC Override Timing

Z C

2 M W

1 M W

A C

Fig.6 ZC Application Example