CAT3637HV3-GT2 Datasheet, PDF (10/14 Pages) ON 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 2mA in all channels. On each
consecutive pulse, the current is incremented by 2mA.
On the 15^th pulse, the current is equal to the full scale
of 30mA. On the following pulse (16^th pulse), the
current goes back to zero and the previous sequence
can be repeated. The EN/SET pin can be pulsed at
high frequency 15 times to decrement the current by
2mA or to program the current from 0mA to 30mA.
The maximum EN/SET signal frequency for
programming the LED current is 2.5MHz.
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 1.5ms or more. The driver typically
powers-down with a delay of about 1ms.
Figure 3. EN/SET One Wire Addressable Timing Diagram
T_HI
EN/SET
LED
Current
Shutdown
T_D
0mA
T_LO
28mA ^30mA
2mA ^{4mA 6mA}
T_OFF
0mA ^2mA
Shutdown
Figure 4. EN/SET Program Increasing / Decreasing LED Current by 2mA
Doc. No. MD-5033 Rev. C
10
© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice