TLC5929 Datasheet, PDF (30/36 Pages) Texas Instruments – 16-Channel, Constant-Current LED Driver with 7-Bit Global Brightness Control, Power-Save Mode

TLC5929
SBVS159 – APRIL 2011
www.ti.com
PRE-THERMAL WARNING (PTW)
The PTW function indicates that the device junction temperature is high. The PTW is set and all LSD data bits
are set to '1' while the device junction temperature exceeds the temperature threshold (T_PTW = +138°C, typ);
however, the outputs are not forced off. When the PTW indicates a high temperature, the device temperature
should be reduced by lowering the power dissipated in the driver to avoid a forced shutdown by the thermal
shutdown circuit. This reduction can be accomplished by lowering the values of the BC data or the LED supply
voltage. The PTW remains '1' until the next rising edge on LAT, even if the temperature drops below T_PTW.
Figure 31 shows a timing diagram and Table 13 shows the truth table for PTW.
CURRENT REFERENCE (IREF PIN) SHORT FLAG (ISF)
The ISF function indicates that the IREF pin is shorted with low impedance to GND. When ISF is set, all OLD
data bits are set to '1'. Then all outputs (OUTn) are forced off and remain off until the short is removed. Table 13
shows the truth table for ISF.
NOISE REDUCTION
Large surge currents may flow through the device and the board on which the device is mounted if all 16 outputs
turn on simultaneously when BLANK goes low or on/off data change at the LAT rising edge with BLANK low.
These large current surges could introduce detrimental noise and electromagnetic interference (EMI) into other
circuits. The TLC5929 turns the outputs on with a 2-ns series delay for each output in order to provide a circuit
soft-start feature.
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