點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
新竹市科學園區展業一路9號7樓之1
9-7F-1, Prosperity RoadⅠ, Hsin-Chu, Taiwan, R.O.C.
DD312
Tel：886-3-5645656
Fax：886-3-5645626
Alarm Function (SOP8 Only)
It can detect the operating status by connecting a pull-high resistor to the open-drain ALARM
pin. The ALARM pin is kept ‘H’ for normal conditions, and shifted to ‘L’ if there is any failure like
LED open, overheating or both occurrence. User can determine the different status from the truth
table below:
ALARM
EN
Status
Normal Operation
H
don’t care
LED Open or Thermal issue
Thermal Alarm or Shutdown
HÆL
HÆL
H
L
Thermal Alarm and Shutdown
During operation, when the junction temperature of the IC will reach about 110℃, the ALARM
pin will shift to low level and produce a warning signal. Suggested cooling measures is to start the
fan, lower the output currents and etc. If no cooling measures were activated, the junction
temperature might continue to rise. Once it reaches approximately above 180℃, it will cause the
driver to shutdown all the outputs. Basically, the IC will cool down and return to the safe operating
temperature which is approximately below 110℃. The ALARM pin will reset to high level, disable
the warning, and restart all the outputs at the same time. Operation in the thermal situation for a long
time may cause chip damage permanently.
HIGH CONSTANT CURRENT LED DRIVER
Version:A.001
Page 7
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