VCC (V

)

LED

GND

SDI

Connector (Male)

To

N+2nd

Device

PCB

To N-1st

Device

PCB or

Controller

and Power

Supply

N+1st Device PCB

Nth Device PCB

TLC5973

www.ti.com

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.

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.

Copyright © 2013–2014, Texas Instruments Incorporated

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