TLC5947_17 Datasheet, PDF (13/33 Pages) Texas Instruments – 24-Channel, 12-Bit PWM LED Driver With Internal Oscillator

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TLC5947
SBVS114B – JULY 2008 – REVISED JANUARY 2015
Feature Description (continued)
When the IC is powered on, the data in the grayscale data shift register and latch are not set to default values.
Therefore, grayscale data must be written to the GS latch before turning on the constant-current output. BLANK
should be at a high level when powered on to keep the outputs off until valid grayscale data are written to the
latch. This avoids the LED being randomly illuminated immediately after power-up. If having the outputs turn on
at power-up is not a problem for the application, then BLANK does not need to be held high. The grayscale
functions can be controlled directly by grayscale data writing, even though BLANK is connected to GND.
BLANK
Counter Value
Internal
Oscillator
Clock
OUTn OFF
(GS Data = 000h) _ON
OUTn ^OFF
(GS Data = 001h) _ON
OUTn ^OFF
(GS Data = 002h) _ON
OUTn ^OFF
(GS Data = 003h) _ON
000012 3
64 66
63 65
1027 1030
2049 2052
1026 1029
2048 2051
1025 1028 1031 2047 2050
3073 3076
3072 3075
3071 3074 3077
4096
4095
4094
12
Grayscale counter starts to count from 5th clock of the internal oscillator clock after BLANK goes low.
Drivers do not turn on when grayscale data are ‘0’.
T = Internal CLK ´ 1
Dotted line indicates BLANK is high.
T = Internal CLK ´ 2
T = Internal CLK ´ 3
OUTn ^OFF
(GS Data = 03Fh) _ON
OUTn ^OFF
(GS Data = 040h) _ON
OUTn ^OFF
(GS Data = 041h) _ON
T = Internal
CLK ´ 63
T = Internal CLK ´ 64
T = Internal CLK ´ 65
OUTn ^OFF
(GS Data = 400h) _ON
OUTn ^OFF
(GS Data = 401h) _ON
T = Internal CLK ´ 1024
T = Internal CLK ´ 1025
OUTn ^OFF
(GS Data = 800h) _ON
T = Internal CLK ´ 2048
OUTn ^OFF
(GS Data = C00h) _ON
T = Internal CLK ´ 3072
OUTn ^OFF
(GS Data = FFEh) _ON
OUTn ^OFF
(GS Data = FFFh) _ON
T = Internal CLK ´ 4094
T = Internal CLK ´ 4095
Figure 18. PWM Operation
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