TLC5946_16 Datasheet, PDF (20/41 Pages) Texas Instruments – 16-Channel, 12-Bit PWM LED Driver with 6-Bit Dot Correction

TLC5946
SLVS824B – MARCH 2008 – REVISED JUNE 2008 .......................................................................................................................................................... www.ti.com
NOISE REDUCTION
Large surge currents can flow through the IC and the board if all 16 LED channels fully turn on simultaneously at
the start of each grayscale cycle. These large current surges could introduce detrimental noise and
electromagnetic interference (EMI) into other circuits. The TLC5946 turns on the LED channels in a series delay,
to provide a current soft-start feature. The output current sinks are grouped into four groups of four channels
each. The first group is OUT0, 4, 8, 12; the second group is OUT1, 5, 9, 13; the third group is OUT2, 6, 10, 14;
and the fourth group is OUT3, 7, 11, 15. Each group turns on sequentially with a small delay between groups;
see Figure 12. Both turn-on and turn-off are delayed.
OUTPUT ENABLE
When BLANK is high, all constant current outputs turn off and the grayscale counter is reset. When BLANK is
low, all constant current outputs are controlled by the GS PWM timing controller. If BLANK goes low and then
toggles high again in a very short time, all outputs that are programmed to turn on do so, for either the
programmed number of grayscale clocks or the length of time that the BLANK signal was low, whichever is
lower. For example, if all outputs are programmed to turn on for 1 ms, but the BLANK signal is only low for 50 ns,
all outputs turn on for 50 ns, even though some outputs will turn on after the BLANK signal has already gone
high.
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