TLC5946_16 Datasheet, PDF (15/41 Pages) Texas Instruments – 16-Channel, 12-Bit PWM LED Driver with 6-Bit Dot Correction

TLC5946
www.ti.com .......................................................................................................................................................... SLVS824B – MARCH 2008 – REVISED JUNE 2008
MSB
95
DC 15.5
90
89
DC 15.0 DC 14.5
6
DC 1.0
5
DC 0.5
LSB
0
DC 0.0
DC OUT15
DC OUT14 to DC OUT1
DC OUT0
Figure 23. Dot Correction Serial Data Configuration
GRAYSCALE (GS) FUNCTION (PWM Operation)
The pulse width modulation (PWM) operation is controlled by a 12-bit grayscale counter that is clocked on each
rising edge of the grayscale reference clock (GSCLK). The counter is reset to zero when the BLANK signal is set
high. The counter value is held at zero while BLANK is high, even if the GSCLK input toggles high and low. After
the falling edge of BLANK, the counter increments with each rising edge of GSCLK. Any constant current sink
output (OUT0 through OUT15) with a non-zero value in its corresponding grayscale latch starts to sink current
after the first rising edge of GSCLK following a high-to-low transition of BLANK. The internal counter keeps track
of the number of GSCLK pulses. Each output channel stays on as long as the internal counter is equal to or less
than the respective output GS data. Each channel turns off at the rising edge of GSCLK when the grayscale
counter value is larger than the grayscale latch value.
For example, an output that has a grayscale latch value of '1' turns on at the first rising edge of GSCLK after
BLANK goes low. It turns off at the second rising edge of GSCLK. Figure 24 shows the PWM output timing.
When the counter becomes FFFh, the counter stops and output does not turn on until the next grayscale cycle.
Pulling BLANK high before the counter becomes FFFh immediately resets the counter to zero.
BLANK
GSCLK
1
2
3
4095 4096
OUTn
(GS Data = 0d)
OUTn
(GS Data = 1d)
OUTn
(GS Data = 2d)
OFF
OFF
t_OUTON = t_GSCLK ´ 1
ON
t_OUTON = t_GSCLK ´ 2
OUTn
(GS Data = 4094d)
OUTn
(GS Data = 4095d)
t_OUTON = t_GSCLK ´ 4094
t_OUTON = t_GSCLK ´ 4095
Figure 24. PWM Output Timing
Copyright © 2008, Texas Instruments Incorporated
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