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[ LP8860-Q1 ] Low Vin Operation

Kenichiro
Mastermind 9165 points
Other Parts Discussed in Thread: LP8860-Q1

[ LP8860-Q1 ] Low Vin Operation

Hi,

When I evaluate LP8860Q1-EVM together with LED Load Board, and decrease the input voltage, from certain Vin, LED start flashing and Boost Overcurrent Fault is toggled. Here is my test conditions.

  • LP8860-Q1EVM
  • J8 is VBUS (LP8860-Q1 VDD is supplied from VBUS)
  • LED Load Board with 8series/4strings
  • Boost Frequency: 303.45KHz w/ and w/o Spread Spectrum
  • Brightness: 100% with 150mA current scale

On this condition, when Vin reach to around 12.3V(w/o SS) / 12.7V(w/ SS), LED start flashing.

Can you help me to understand why this happen?

I need to reduce Vin further down to 4.5V as system requirement.

Thank you for your support in advance.

Regards,

Ken

  • 0
    TI__Genius 11020 points

    Hello Ken,

    What is the BOOST_IMAX_SEL setting you have now? It sounds like it is set too low for this condition. Peak inductor current will be >2A in this condition. What is the current limit on your power supply? Does the input voltage stay stable when LP8860 enters fault recovery state?

    You could also try sourcing the VDD from external power supply, not from the USB.

    Thanks.

    Best Regards,

    Tomi Koskela