LP8557: Paralleling the Outputs

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Part Number: LP8557

Team,

Can the LED outputs be connected in parallel?

The max current through a single channel is 25 mA. Our LCD backlight requires 40mA. My thought is if the LED string was fed into channel 1 and 2, then there would be 50mA. Then the rest of the channels will turn off due to auto-detect feature which turns off unused LED output channels.

I’m concerned regarding the phase shifting scheme. If two LED channels are connected together to get a greater current capability, does the PWM phasing have any noticeable effect?

over 3 years ago

0 Yuting Shao over 3 years ago

TI__Genius 13001 points

Hi,

If you combine two channels together, then phase shift function will be disable.

Robin

0 Steve Widener over 3 years ago in reply to Yuting Shao

TI__Genius 9805 points

Although the PWM scheme is disabled, will the driving still be able to drive 0-40 mA?

I’m seeing that another user on the TI forum is seeing errors in the STATUS register while connecting the outputs in parallel which is making me a little concerned that this might not work with this chip:

(https://e2e.ti.com/support/power-management/f/196/p/976521/3628319#3628319)

0 Yuting Shao over 3 years ago in reply to Steve Widener

TI__Genius 13001 points

Hi,

This device supports output channels in parallel. But, you should set the adaptive dimming threshold 0% (please refer to 8.1.6.7 of the datasheet) first, then phase shift function has no any impact.

Robin

Power management

Power management forum

LP8557: Paralleling the Outputs