Datasheet

t (ns)=t (ns) GSXn
OUT_ON GSCLK
´
TLC59711
www.ti.com SBVS181A –OCTOBER 2011–REVISED JULY 2012
GRAYSCALE (GS) FUNCTION (PWM CONTROL)
The TLC59711 can adjust the brightness of each output channel using the enhanced spectrum pulse width
modulation (ES-PWM) control scheme. The PWM bit length for each output is 16 bits. The use of the 16-bit
length results in 65536 brightness steps from 0% to 100% brightness.
The PWM operation for all color groups is controlled by a 16-bit grayscale (GS) counter. The GS counter
increments on each rising or falling edge of the external or internal GS reference clock that is selected by
OUTTMG (bit 217) and EXTGCK (bit 216) in the data latch. When the external GS clock is selected, the GS
counter uses the SCKI clock as the grayscale clock. The GS counter is reset to 0000h and all outputs are forced
off when BLANK (bit 213) is set to '1' in the data latch and the counter value is held at '0' while BLANK is '1',
even if the GS reference clock is toggled in between.
Equation 3 calculates each output (OUTXn) total on-time (t
OUT_ON
):
Where:
t
GSCLK
= one period of the selected GS reference clock
(internal clock = 100ns typical, external clock = the period of SCKI)
GSXn = the programmed GS value for OUTXn (0d to 65535d) (3)
Table 3 summarizes the GS data values versus the output total on-time and duty cycle. When the IC is powered
up, BLANK (bit 213) is set to '1' to force all outputs off; however, the 224-bit shift register and the 218-bit data
latch are not set to default values. Therefore, the GS data must be written to the data latch when BLANK (bit
213) is set to '0'.
Table 3. Output Duty Cycle and Total On-Time versus GS Data
GS DATA (decimal) GS DATA (hex) ON-TIME DUTY (%) GS DATA (decimal) GS DATA (hex) ON-TIME DUTY (%)
0 0 0 32768 8000 50.001
1 1 0.002 32769 8001 50.002
2 2 0.003 32770 8002 50.004
3 3 0.005 32771 8003 50.005
— — — — — —
8191 1FFF 12.499 40959 9FFF 62.499
8192 2000 12.5 40960 A000 62.501
8193 2001 12.502 40961 A001 62.502
— — — — — —
16383 3FFF 24.999 49149 BFFF 74.997
16384 4000 25 49150 C000 74.998
16385 4001 25.002 49151 C001 75
— — — — — —
24575 5FFF 37.499 57343 DFFF 87.5
24576 6000 37.501 57344 E000 87.501
24577 6001 37.502 57345 E001 87.503
— — — — — —
32765 7FFD 49.996 65533 FFFD 99.997
32766 7FFE 49.998 65534 FFFE 99.998
32767 7FFF 49.999 65535 FFFF 100
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