For2CHHVMmode:V

=19.2V

LSD

For4/8CHHVMmodes:V

=8

HVM4(V)

´

LSD

Dn

HVM4

(4CH,8CH

HVMModes)

V

LED

LEDShort

(LSD)

Failure

Recognition

Logic

Routine

LEDOpen

(LOD)

ComparisonVoltage:

LEDShort=19.2Vtyp

LEDOpen=0.8Vtyp

ErrorDetection

Comparator

EN

TLC5960

SBVS147 – SEPTEMBER 2010

www.ti.com

LED OPEN DETECTION (LOD) AND LED SHORT DETECTION (LSD)

The TLC5960 senses the drain node of the external FET when the FET is on, as shown in Figure 21. When the

LED is open, the drain voltage falls below the default detection level (0.8V). The LED short detection (LSD)

triggers at an abnormal overvoltage detection threshold of 19.2V, typically. This LSD detection threshold can be

redefined in the 4CH and 8CH HVM modes according to the various system configurations. The threshold is

defined by Equation 4 and Equation 5.

For example, when detecting two shorted LEDs on an 15-LED string, this voltage range can be set to ~10V

(HVM4 input = 1.25V) in 4CH and 8CH HVM modes. This ~10V voltage setting can be calculated by multiplying

to 2.6V). In the case of LDO and LSD, the TLC5960 shuts off the failed LED string(s) and automatically

separates the failed string(s) from the operating strings.

(4)

(5)

Figure 21. TLC5960 Drain Terminals Sensing to Protect LED Failure

18

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