TLC5973 Datasheet, PDF (13/34 Pages) Texas Instruments – TLC5973 3-Channel, 12-Bit, PWM Constant-Current LED Driver with Single-Wire Interface (EasySet)

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TLC5973
SBVS225B – MARCH 2013 – REVISED MAY 2014
8.3.5 Connector Design
When the connector pin of the device application printed circuit board (PCB) is connected or disconnected to
other PCBs, the power must be turned off to avoid device malfunction or failure. Furthermore, designing the
connector GND pin to be longer than other pins (as shown in Figure 12) is preferable. This arrangement allows
the GND line to either be connected first or disconnected last, which is imperative for proper device function.
To N-1st
Device
PCB or
Controller
and Power
Supply
Nth Device PCB
GND
VCC (V_LED)
N+1st Device PCB
To
N+2nd
Device
PCB
SDI
Connector (Male)
Figure 12. Connector Pin Design Application
8.4 Device Functional Modes
8.4.1 Grayscale (GS) Function (PWM Control)
The TLC5973 can adjust the brightness of each output channel using a pulse width modulation (PWM) control
scheme. The PWM data bit length for each output is 12 bits. The architecture of 12 bits per channel results in
4096 brightness steps, from 0% to 99.98% on-time duty cycle.
The PWM operation for OUTn is controlled by an 12-bit grayscale (GS) counter. The GS counter increments on
each internal GS clock (GSCLK) rising edge. All OUTn are turned on when the GS counter is ‘1’, except when
OUTn are programed to GS data '0' in the 36-bit GS data latch. After turning on, each output is turns off when
the GS counter value exceeds the programmed GS data for the output. The GS counter resets to 000h and all
outputs are forced off when the GS data are written to the 36-bit GS data latch. Afterwards, the GS counter
begins incrementing and PWM control is started from the next internal GS clock.
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