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| TLC5942_16 Datasheet, PDF (18/29 Pages) Texas Instruments – 16-Channel, 12-Bit PWM LED Driver with 7-Bit Dot Correction | |||
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TLC5942
Not Recommended for New Designs
SBVS096B â OCTOBER 2007 â REVISED OCTOBER 2007
www.ti.com
When the IC is powered on, the data in the Grayscale Shift Register and latch are not set to any default value.
Therefore, Grayscale data must be written to the Grayscale latch before turning the constant current output on.
Additionally, BLANK should be high when the device turns on, to prevent the outputs from turning on before the
proper grayscale and dot correction values can be written. All constant current outputs are always off when
BLANK is high. Equation 3 determines each output (OUTn) on time (tOUTON):
tOUTON (ns) = TGSSCLK (ns) ´ GSn
(3)
Where:
TGSSCLK = the period of GSSCLK
GSn = the programmed grayscale value for OUTn (GSn = 0 to 4095d)
If there are any unconnected output LED lamps (including connection failures or short-circuits), the grayscale
data corresponding to the unconnected output should be set to '0' before turning on the LEDs. Otherwise, the
supply current (IVCC) increases while the LEDs are on. If GS data changes during a GS period because XLAT
goes high, and latches new GS data, the internal data latch registers are immediately updated. This action can
cause the outputs to turn on or off unexpectedly. For proper operation, GS data should only be latched into the
IC at the end of a GS period when BLANK is high. Table 3 summarizes the GS data versus OUTn on duty and
on time.
GS DATA
(Binary)
0000 0000 0000
0000 0000 0001
0000 0000 0010
0000 0000 0011
... ...
0111 1111 1111
1000 0000 0000
1000 0000 0001
... ...
1111 1111 1101
1111 1111 1110
1111 1111 1111
Table 3. GS Data versus OUTn On Duty and OUTn On Time
GS DATA
(Decimal)
0
1
2
3
... ...
2047
2048
2049
... ...
4093
4094
4095
GS DATA
(Hex)
000
001
002
003
... ...
7FF
800
801
... ...
FFD
FFE
FFF
OUTn
ON DUTY (%)
0.00
0.02
0.05
0.07
... ...
49.99
50.01
50.04
... ...
99.95
99.98
100.00
OUTn ON TIME (ns, typical)
AT 30 MHz GSSCLK
0
33
67
100
... ...
68263
68267
68300
... ...
136433
135467
136500
18
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Product Folder Link(s): TLC5942
Copyright © 2007, Texas Instruments Incorporated
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