TLC5902 Datasheet, PDF (15/22 Pages) Texas Instruments – LED DRIVER

WDT Operational Time
PRINCIPLES OF OPERATION
T (ms) ≅ 3+0.03 × C1 (pF)
TLC5902
LED DRIVER
SLLS382 – DECEMBER 1999
3000
300
33
Scan Signal
C1
TLC5902
WDT
WD_CAP
Figure 2. WDT Usage Example
3
0
103
104
105
C1 – External Capacitor – pF
Figure 1. WDT Operational Time
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.
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