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.
DM634
Tel：886-3-5645656
Fax：886-3-5645626
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*1 set “L”, it will be identified as a LED open failure
when the output is turned on but the output voltage is below 0.3V. The test result of each channel
will write to its correspondent shift register which is in LSB position (D15[0], D14[0], …., D0[0])
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
180℃, driver will shutdown all the outputs. Basically, the chip will cool down and return to the
safe operating temperature which is approximately below 110℃. DM634 will restart all the outputs
at the same time. Operating upon 180℃ may cause chip to be damaged permanently.
Normal
Shutdown
Shutdown
Normal
Alarm
T(
℃
)
180
℃
110
℃
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
shift register which is in the position (D255[0]) while strobe signal is active. User can refer to timing
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’ .
*1 “L” is the default value of O/S flag. User can refer to Global Brightness Control to know how to set O/S flag on page
16.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.003
Page 11
未經授權而逕予重製、複製、使用或公開本文件，行為人得被追究侵權之相關民刑事責任
Unauthorized reproduction, duplication, use or disclosure of this document will be deemed as infringement.
SITI [ SILICON TOUCH TECHNOLOGY INC. ]
