TLC5952 Datasheet, PDF (23/33 Pages) Texas Instruments – 24-Channel, Constant-Current LED Driver with Global Brightness Control and LED Open-Short Detection

TLC5952
www.ti.com........................................................................................................................................................................................................ SBVS129 – MAY 2009
As shown in Table 5, LOD and LSD data cannot be checked simultaneously. LOD/LSD data are not valid when
TEF is active because all outputs are forced off.
The TEF bit indicates that the IC junction temperature exceeds the temperature threshold (T_TEF = +165°C, typ).
The TEF bit also indicates that the IC has turned off all drivers to avoid overheating. The IC automatically turns
the drivers back on when the IC temperature decreases to less than T_TEF – T_HYS. The TEF data are held in the
TEF holder latch until the TEF data are loaded into the common shift register by the rising edge of LAT. If the IC
temperature falls below T_TEF – T_HYS when LAT goes high, the TEF data in the TEF holder become '0'. If the IC
temperature is not below T_TEF – T_HYS when LAT goes high, then the TEF data remain '1'. Table 5 shows a truth
table for LOD/LSD and TEF. Figure 36 to Figure 39 show different examples of LOD/LSD/TEF operation.
SID DATA
0
1
Table 5. LOD/LSD/TEF Truth Table
LED OPEN DETECTION
(LOD, Voltage Select Data =
0h to 3h)
LED is not open or the output is off
(V_OUTRn/Gn/Bn is greater than the
voltage selected by the detection
voltage select bit in the
control data latch)
LED is open or shorted to GND
(V_OUTRn/Gn/Bn is less than or equal to
the voltage selected by the detection
voltage select bit in the
control data latch)
CONDITION
LED SHORT DETECTION
(LSD, Voltage Select Data = 4h to 7h)
THERMAL ERROR FLAG (TEF)
LED is not shorted or the output is off
(V_OUTRn/Gn/Bn is less than or equal to
the voltage selected by the detection
voltage select bit in the
control data latch)
Junction temperature is lower than the
detect temperature (T_TEF) before TEF
is undetected or the detect temperature
(T_TEF – T_HYS) after TEF is detected
LED terminal is short or OUTn is short
to higher voltage (V_OUTn is greater than
The selected voltage by detection
voltage select bit in the
control data latch)
Junction temperature is higher than the
detect temperature (T_TEF)
THERMAL SHUTDOWN (TSD)
The thermal shutdown (TSD) function turns off all constant-current outputs when the IC junction temperature (T_J)
exceeds the temperature threshold (T_TEF = +165°C, typ). The outputs remain disabled as long as the
over-temperature condition exists. The outputs are turned on again after the IC junction temperature drops below
(T_TEF – T_HYS).
NOISE REDUCTION
Large surge currents may flow through the IC and the board on which the device is mounted if all 24 LED
channels turn on simultaneously when BLANK goes low. These large current surges could induce detrimental
noise and electromagnetic interference (EMI) into other circuits. The TLC5952 turns the LED channels on in a
series delay to provide a circuit soft-start feature.
A small delay circuit is implemented between each output. When all bits of the on/off data latch are set to '1',
each constant-current output turns on in order (OUTR0, OUTG0, OUTB0, OUTR1, OUTG1, OUTB1,
OUTR2-OUTB6, OUTR7, OUTG7, and OUTB7) with a small delay between each output after BLANK goes low
or LAT goes high; see Figure 34. Both turn-on and turn-off are delayed.
CAPACITOR SELECTION
Connect at least one 10-nF ceramic capacitor as close as possible between the V_CC pin and ground. Additional
capacitors are needed on the LED power supply to reduce ripple on the LED power supply to a minimum.
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): TLC5952
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