HT761X
MODE
MODE is a tri-state input pin used to select the
operating mode.
MODE Operating
Status Mode
Description
VDD
Output is always ON:
RELAY outputs high for
ON
relay driving.
TRIAC pulse train output
is synchronized by ZC for
triac driving.
VSS
OFF
Output is always OFF:
RELAY outputs low for
relay driving.
TRIAC outputs high 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 chip
allows override control by
switching the ZC signal.
ZC
ZC is a CMOS input structure. It receives AC
line frequency and generates zero crossing
pulses to synchronize the triac driver. By effec-
tive ZC signal switching (switch OFF/ON 1 or 2
times within 3 seconds by mask option), the
chip provides the following additional func-
tions:
• Test mode control
Within 10 seconds after power-on, effective
ZC switching will force the chip to enter the
test mode. During the test mode, the outputs
will be active for a duration of 2 seconds each
time a valid PIR trigger signal is received. If
a time interval exceeds 32 seconds without a
valid trigger input, the chip will enter the
AUTO mode automatically.
7
24th Mar ’97