LED171596ARSLR datasheet(19/153 Pages) TI1

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LED171596A

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SNVSAY2 – OCTOBER 2017

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with DRV_HEADROOM bits)

•

Detection

–

The LED open and short comparators are sampled after a blanking window following the start of the PWM

cycle.

–

The output of each comparator is held until latched by fault detection 6 μs after the start of the PWM cycle

when pwm_freq_sel = 1.

–

The LED faults are evaluated over a detection window of 16 HS cycles to avoid false fault detection.

–

In order for the LED fault condition to be detected it must be continuously present for one full detection

window.

–

Because the fault condition can occur just following the first PWM cycle in a detection window the LED

fault detection can vary from 16 to 31 HS cycles (1.55 to 3.1 ms when pwm_freq_sel=1).

–

LED open and short detection only performed when brightness is greater than 10 dec (> 500 ns on-time

pulse when pwm_freq_sel=1).

–

Ghosting cancellation will be disabled for the phase where shorted LED has been detected and will remain

disabled until the LED fault has been cleared.

•

Action:

–

LEDs do not disable automatically (user can program brightness to zero)

–

LED_OPEN_INT_EN and LED_SHORT_INT_EN define whether fault/interrupt pin is set (default stored in

EPROM bits)

–

Global LED Short and LED Open bits are set.

–

LED

fault

signals

stored

internally

and

can

read

with

the

LEDXX_XX_OPEN

and

LEDXX_XX_SHORT registers. Also, a global LED_OPEN and LED_SHORT bit is set when any of the

individual bits are set.

–

o LED fault status cleared by writing CLEAR_LED_OPEN or CLEAR_LED_SHORT bits in the

INT_CLEAR register.

–

The correct procedure for clearing faulty LED is to disable the failing LED by setting ledxx_xx_disable

bit = 1 in the LEDxx_xx_DISABLE register at least 3.1 ms before clearing the LED fault.

LED171596ARSLR Datasheet(PDF) 19 Page - Texas Instruments

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