CAT3637 Datasheet, PDF (11/14 Pages) Catalyst Semiconductor – 6-Channel Programmable High Efficiency Quad-Mode™ LED Driver

CAT3637
LED Current Setting
The current in each of the six LED channels is
programmed through the 1−wire EN/SET digital control
input. At the initial power−up and once the EN/SET is set
high, the LED current remains at zero in all channels. On the
first EN/SET pulse (positive edge), the current is set to 2 mA
in all channels. On each consecutive pulse, the current is
incremented by 2 mA. On the 15^th pulse, the current is equal
to the full scale of 30 mA. On the following pulse (16^th
pulse), the current goes back to zero and the previous
T_HI
sequence can be repeated. The EN/SET pin can be pulsed at
high frequency 15 times to decrement the current by 2 mA
or to program the current from 0 mA to 30 mA. The
maximum EN/SET signal frequency for programming the
LED current is 2.5 MHz.
To power−down the device and turn−off all current
sources, the EN/SET input should be kept low for a duration
T_OFF of 1.5 ms or more. The driver typically powers−down
with a delay of about 1 ms.
EN/SET
LED
Current
Shutdown
T_LO
T_OFF
T_D
28 mA 30 mA
0 mA
2 mA ^{4 mA 6 mA}
0 mA ^{2 mA}
Figure 24. EN/SET One Wire Addressable Timing Diagram
Shutdown
Figure 25. EN/SET Program Increasing / Decreasing LED Current by 2 mA
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