TLC5902

LED DRIVER

SLLS382 – DECEMBER 1999

15

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

Figure 1. WDT Operational Time

3000

300

33

3

0103

104

105

C1 – External Capacitor – pF

WDT Operational Time

T (ms)

≅ 3+0.03 × C1 (pF)

Figure 2. WDT Usage Example

TLC5902

WDT

WD_CAP

Scan Signal

C1

TSD (thermal shutdown)

When the junction temperature exceeds the limit, TSD functions and turns the constant current output off. When

TSD is used, TS_ENA is pulled high. When TSD is not used, TS_ENA is pulled low. To recover to normal

operation, the power supply is turned off or TS_ENA is pulled low.

noise reduction

concurrent switching noise reduction

The concurrent switching noise has a potential to occur when multiple outputs turn on or off at the same time.

To prevent this noise, the device has delay output terminals such as GSOUT and BOUT for GSCLK and BLANK

respectively. Connecting these outputs to GSCLK and BLANK terminals of the next stage IC allows differences

in the switching time between ICs to be made. When GSCLK is output to GSOUT through the device, duty is

changed, so that the number of stages to be connected will be limited to a maximum of 10 at GSCLK = 4 MHz.

output slope

The on and off time of constant current output at an output current of 80 mA is approximately 150 ns and 250 ns

respectively. It is effective in reducing concurrent switching noise that occurs when multiple outputs turn on or

off at the same time.

delay between constant current output

The constant current output has a delay time of approximately 8 ns between output. It means approximately

120 ns delay time exists between OUT0 and OUT15. This time difference by delay is effective for reduction of

concurrent switching noise as well as output slope. This delay time has the same value at 8-bits or 16-bits

operation mode.