THERMAL SHUTDOWN (TSD)

NOISE REDUCTION

CAPACITOR SELECTION

TLC5952

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 also indicates that the IC has turned off all drivers to avoid overheating. The IC automatically turns

TEF holder latch until the TEF data are loaded into the common shift register by the rising edge of LAT. If the IC

table for LOD/LSD and TEF. Figure 36 to Figure 39 show different examples of LOD/LSD/TEF operation.

Table 5. LOD/LSD/TEF Truth Table

CONDITION

LED OPEN DETECTION

(LOD, Voltage Select Data =

LED SHORT DETECTION

SID DATA

0h to 3h)

(LSD, Voltage Select Data = 4h to 7h)

THERMAL ERROR FLAG (TEF)

LED is not open or the output is off

LED is not shorted or the output is off

Junction temperature is lower than the

0

voltage selected by the detection

the voltage selected by the detection

is undetected or the detect temperature

voltage select bit in the

voltage select bit in the

control data latch)

control data latch)

LED is open or shorted to GND

LED terminal is short or OUTn is short

Junction temperature is higher than the

1

the voltage selected by the detection

The selected voltage by detection

voltage select bit in the

voltage select bit in the

control data latch)

control data latch)

over-temperature condition exists. The outputs are turned on again after the IC junction temperature drops below

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.

capacitors are needed on the LED power supply to reduce ripple on the LED power supply to a minimum.

Copyright © 2009, Texas Instruments Incorporated

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Product Folder Link(s): TLC5952