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Original question:

LM3643: LM3643

LM3643: Brightness value of driven LED is much lower than the one in TORCH register when STROBE and TX are HIGH

Pasquale Longo
Prodigy 10 points
Part Number: LM3643
Other Parts Discussed in Thread: LM3644EVM,

I am using LM3643EVM, VIN=5V, L1 inductor short circuited, device configured in PASS MODE only.

I set the brightness value in the TORCH brightness register to ~50mA and in FLASH brightness register to ~100mA.

I set TX pin to HIGH and I use the STROBE pin to switch ON and OFF the LED. What I expect is the LED to be driven at ~50mA (the value stored in the TORCH brightness register), but what I observe is that the LED is driven at ~2mA.

If TX pin is held LOW, the current I observe is the same as programmed in the FLASH brightness register, so no problem.

Flashing time is lower than the one chosen in the Flash time-out duration register.

Can you please advice why holding the TX pin HIGH while commuting STROBE pin only results in a negligible current delivered (instead of the value stored in the TORCH brightness register)?

Thank you!