TLC5954 Datasheet, PDF (34/45 Pages) Texas Instruments – TLC5954 48-Channel, Constant-Current LED Driver with Global Brightness Control, LED Open-Short Detection, and Power-Save Mode

TLC5954
SBVS241 – APRIL 2014
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9.2.2 Detailed Design Procedure
9.2.2.1 Step-by-Step Design Procedure
To begin the design process, a few parameters must be decided upon. The designer needs to know the
following:
• Maximum output constant-current value for all colors of the LED ramp.
• Maximum LED forward voltage (V_F).
• Current ratio of red, green, and blue LED lamps for the best white balance.
• Is the LED open detect (LOD) function used? If so, which detection level (0.20 V, 0.30 V, 0.40 V, 0.50 V, or
0.60 V) is used?
• Is the LED short detect (LSD) function used? If so, which detection level (50% VCC, 70% VCC, or 90% VCC)
is used?
9.2.2.2 Maximum Current (MC) Data
There are a total of three bits of MC data that set the output current of all constant-current outputs (OUTXn).
Select the MC data to be greater than the target LED ramp current if the output current is reduced white
balanced by the global brightness control data and write the data with other control data.
9.2.2.3 Global Brightness Control (BC) Data
There are a total of three sets of 7-bit BC data for the red, green, and blue LED ramp. Select the BC data for the
best white balance of the red, green, and blue LED ramp and write the data with other control data.
9.2.2.4 On or Off Data
There are a total of 48 bits of on or off data for the on or off control of each output. Select the on or off data of
the LED lamp on or off status control and write the data.
9.2.2.5 Other Control Data
There are a total of 8 bits of control data to set the function mode for the status information data (SID) load
control, LOD voltage setting, LSD voltage setting, and power save mode (PSM) explained in the Device
Functional Modes section. Write the 8-bit control data for the appropriate operation of the display system with MC
and BC data as the control data.
9.2.2.6 Grayscale Control
All constant-current outputs are controlled by the BLANK pin logic level. When BLANK is GND, all constant-
current outputs are turned on except that the output is set to 0 in the 48-bit output on-off data latch. When
BLANK is VCC, all outputs are forced off. The LED lamp grayscale can be controlled by the BLANK low pulse
duration.
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