0.5 Ps

1.0 Ps

1.5 Ps

2.0 Ps

2.5 Ps

3.0 Ps

Time

LM3432, LM3432B

www.ti.com

SNVS498D – APRIL 2007 – REVISED MAY 2013

Figure 15. PWM Dimming Switching Timing

LED SHORT FAULT DETECT

With DHC

If the Dynamic Headroom Control (DHC) feature is used, the lowest voltage between the IOUT pins and ground

exceed the typical short fault threshold of 7.9V for more than 150 µs, the affected channel(s) will be latched off

and the FAULTb pin will be pulled to ground. The affected channel(s) will remain latched off until recycling power

or toggling the EN pin. All of the other channels that are not affected will continue to function normally.

Without DHC

In applications where the DHC function is not used, the IOUT pin voltage on each string will be the voltage

voltage between any of the IOUT pins and ground is less than 2V typical, the short fault detect feature will be

active for all channels. In the event an LED short fault condition occurs and causes the voltage between any of

the IOUT pin and ground to exceed the typical short fault threshold of 7.9V for more than 150

μs, the affected

channel(s) will be latched off and the FAULTb pin will be pulled to ground. The affected channel(s) will remain

latched off until recycling power or toggling the EN pin. All of the other channels that are not affected will

continue to function normally. If the voltages between all IOUT pins and ground are greater than 2V typical, the

Short Fault Detect feature will be disabled to prevent false triggering of the short fault detect function.

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