Other Parts Discussed in Thread: LMR16010, TPS92515, LM3407, LM3405
I am having some trouble with the TPS92510 which I believe is related to the bootstrap capacitor and boot UVLO. My input voltage source is variable and sometimes dips down to around 3.5V-4V. I have found that, when this happens, the TPS92510 stops switching until Vin rises above ~5V. I am driving one 3V LED, so I believe this is related to the boot UVLO - when the input drops low enough that switching stops the boot voltage eventually decays and switching stops, as detailed on page 15 of the datasheet. I seem to be stuck in the case where the output voltage does not decay past the LED forward voltage, so switching only resumes once Vin rises above Vf + BOOT UVLO. The problem is that this causes the LED to flicker at times when the input dips around that threshold.
Other LED drivers I have tested have not had quite this problem. If Vin is too low to drive the LED then current drops until it rises above Vf, and that's fine. But the extra requirement to wait until it rises above Vf + UVLO makes the flickering a real problem.
Is there any additional circuitry that can be added to help with this situation? Tying BOOT to a higher external voltage, or adding a pulldown to SW? I figure that, once switching stops, a resistor can pull down SW to put 2.1V across the BOOT cap fairly quickly, at the cost of a little lost current during normal operation. I tested this with mixed results, but perhaps there is a recommended solution for this?