I am looking to use the LMR36015 in a somewhat uncommon way. My input power supply is a 500mA current source, but with a 30V voltage limit. I normally connect 3 LEDs (total Vf = 9V) to the supply and rely on the 500mA current limit to safely drive the LEDs as the LEDs themselves limit the supply voltage to 9V. I am considering using the LMR36015 (or another similar regulator) between the supply and the LEDs, to give me the option of turning off the LEDs, but still maintaining a voltage of about 5V, allowing me to continue powering other circuitry, but keeping the voltage low enough that the LEDs cannot conduct.
When I want to turn on the LEDs, I set the LMR36015 output voltage to 12V (by adjusting resistors at the FB pin, or driving a DAC voltage to FB pin through a resistor). The input voltage is pulled down to 9V and the LMR36015 operates in dropout mode. If the input voltage had been above 9V, I briefly get some higher current, up to the 1.5A current limit, and it then settles down to the 500mA available from the power supply.
When I want to turn off the LEDs, I set the LM36015 output voltage to 5V. The LEDs turn off but my other circuitry remains powered.
One question is about the current limit and hiccup mode. When I set the output voltage to 12V and I want the LMR36015 to be operating in dropout mode, it is possible that the input voltage could drop and the FB pin could fall below 0.4V. Section 8.3.3 mentions that hiccup mode will occur when this happens, but only during current limit. Can you confirm that? In my situation FB would only drop below 0.4V when the current is much lower, although the part would still be operating in dropout. I would not want this to trigger hiccup mode.
Since this is an unusual application I am open to any other concerns that you might have about using the regulator this way, or any other recommended regulators that could work better for this application.
