TLC5944 Datasheet, PDF (18/34 Pages) Texas Instruments – 16-Channel, 12-Bit PWM LED Driver with 6-Bit Dot Correction and Pre-Charge FET

TLC5944
SBVS112 – JUNE 2008 ...................................................................................................................................................................................................... www.ti.com
When the IC powers 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 on the constant current output.
Additionally, BLANK should be held 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 forced off when
BLANK is high. Equation 3 determines the on time (t_OUTON) for each output (OUTn).
t_OUTON (ns) = t_GSCLK (ns) ´ GSn
(3)
Where:
• T_GSCLK = the period of GSCLK
• GSn = the programmed grayscale value for OUTn (GSn = 0 to 4095d)
If GS data change during a display 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 display 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 RATIO
TO MAXIMUM CODE (%)
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 33-MHz GSCLK
0
30
61
91
---
62030
62061
62091
---
124030
124061
124091
18
Submit Documentation Feedback
Product Folder Link(s): TLC5944
Copyright © 2008, Texas Instruments Incorporated