TLC5955 Datasheet, PDF (17/53 Pages) Texas Instruments – TLC5955 48-Channel, 16-Bit, PWM LED Driver with DC, BC, LED Open-Short Detection, and Internal Current Setting

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TLC5955
SBVS237 – MARCH 2014
8.3 Feature Description
8.3.1 Output Current Calculation
The output current value controlled by MC, DC, and BC can be calculated by Equation 1.
I_OUTn (mA) = I_OLCMax (mA) ´
0.262 + 0.738 ´
DCXn
127
´ 0.10 + 0.90 ´ ^BCX
127
where:
• I_OLCMax = the maximum constant-current value for all OUTXn for each color group programmed by MC data,
• DCXn = the dot correction value for each channel (0h to 7Fh),
• BCX = the global brightness control value (0h to 7Fh),
• X = R, G, or B for the red, green, or blue color group, and
• n = 0 to 15.
(1)
Each output sinks the I_OLCMax current when they turn on and the dot correction (DC) data and the global
brightness control (BC) data are set to the maximum value of 7Fh (127d). Each output sink current can be
reduced by lowering the DC and BC values.
When I_OUT is set lower than 1 mA by both MC and BC or BC only, the output may be unstable. Output currents
lower than 1 mA can be achieved by setting I_OUT to 1 mA with MC and BC or BC only and then using DC to
lower the output current.
8.3.2 Register and Data Latch Configuration
The TLC5955 has one common shift register and three data latches: the grayscale (GS) data latch, the control
data latch, and the dot correction (DC) data latch. The common shift register is 769 bits long, the GS data latch is
768 bits long, the control data latch is 371 bits long, and the DC data latch is 336 bits long.
If the common shift register MSB is 0, the least significant 768 bits from the common shift register are latched
into the GS data latch. If the MSB is 1, and bits 767 to 760 are 96h (10010110b), the data are latched into the
control data latch. Refer to Figure 21 for the common shift register, GS data latch, control data latch, and DC
data latch configurations.
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