Low threshold

Mid threshold (Low + 0.5V)

High threshold

All voltages are above Mid threshold =>

boost voltage needs to be adjusted down!

Low threshold

Mid threshold (Low + 0.5V)

High threshold

This causes the boost

voltage to rise!

Low threshold

Mid threshold (Low + 0.5V)

High threshold

LP8543

www.ti.com

SNVS604D – AUGUST 2009 – REVISED MARCH 2013

Figure 18. Normal Operation, High PWM Value

If one LED driver voltage is below Low, boost voltage will be increased. This is seen in the following figure.

Figure 19. Boost voltage too Low

If all driver voltages are above Mid threshold (or any of the voltages in PSPWM adaptation mode and with low

PWM value), boost voltage will be lowered. Decision is always based on number of strings active at the same

time. In the illustrations 6 outputs are active, which basically means close to 100% PWM value with PSPWM.

Figure 20. Boost voltage too High

Fault Detection

LP8543 has fault detection for LED fault, low-battery voltage, overcurrent and thermal shutdown. The open drain

output pin (FAULT) can be used to indicate occurred fault. The cause for the fault can be read from status

register. Refreshing the <BL_CTL> bit high will reset the fault register and fault pin state.

Copyright © 2009–2013, Texas Instruments Incorporated

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