點晶科技股份有限公司

SILICON TOUCH TECHNOLOGY INC

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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.

Tel：886-3-5645656

Fax：886-3-5645626

16-channel 16-bit PWM Constant Current LED Driver

Version : A.003

Page 11

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DM634

LED Open/Short Detection

DM634 provides a real time monitor of LED open / short detection function without extra

components or circuit design. When O/S flag

when the output is turned on but the output voltage is below 0.3V. The test result of each channel

while strobe signal is active. User can refer to timing diagram on page12. Detecting report could be

retrieved from serial-out (DAO) data. If the system reads ‘1’ back, that indicates LED is in normal

status. But if ‘0’ was retrieved, it means LED open failure has occurred. In the short detection, O/S

flag set “H”. And system reads result as ‘1’ means normal, ‘0’ means LED short failure occurred.

The short detection threshold voltage is 65% of VCC.

In order to make sure LED open/short

detection function is in well operating condition, it is recommended that all the luminance data are

wrote to ‘1’ then almost turning on the outputs during detection process.

Thermal Alarm and Shutdown

During operation, when the junction temperature of the chip reaches approximately above

Shutdown

Alarm

Normal

Normal

Shutdown

DM634 provides a real time monitor of chip thermal alarm and shutdown function. Except

avoid the damage occurs when local junction temperature over the limitation, system can recognize

which chip is under this situation. When O/S flag set “ 0”, it will be identified as the chip thermal

over 110℃ as the THF flag retrieved ‘ 0’. The test result of each chip will write to its correspondent

diagram on page14. Detecting report could be retrieved from serial-out (DAO) data. If the system

reads ‘ 1’ back, that indicates chip is in normal status. But if ‘ 0’ was retrieved, it means the chip

juction temperature is over 180℃ when O/S flag set to ‘ 1’ .

16.