I'm working on a raspberry pi "hat" and as part of that I want to power the pi from the hat. The project needs both a 12v (for motors) and 5v supply (for PI/ICs). Attached is a schematic using the LM2576 (non adjustable 5V out) based on the datasheet's example 12v to 5v step down circuit.
My question is with regards to the D3 diode I've added. As the Raspberry Pi could be powered up at the same time as power is applied to P1, the "hat" spec suggests a protection diode be added. Given that the expected avg current draw is ~1A but there are cases where closer to 2.5A could be drawn for a short time or the entire system could be idling down closer to 0.5A. That diode I think will result in a voltage drop of ~0.2-0.5V depending on load so a final output of 4.8 to 4.5V.
I could switch to the adjustable version of the LM2576 and select R1 and R2 such that the voltage output is a little higher to keep the final output within the 5.2 to 4.9V range depending on load but I'm wondering if there's a better way to handle this?