What is the simplest and cheaper way to have 3.3V 0.5A from 4V?
I'm developing a board which uses a SIM800 so it must have 4V 2A power input from 24V external power supply (I'm using a LM2596S adj, able to supply 4V 3A). SIM800 has 4V Vdd and 3.3V logical input/output.
The rest of the board (microcontroller, etc) needs 3.3V, so I want to take it from the 4V (because if I take it from 24V I would need another step-down converter... and that means more components and cash).
The cheap AMS1117 has 1V dropout voltage, so it's not suitable. The cheap MCP1700 has only 250mA output current.
What's about to use diodes to get this voltage? There is another cheap regulator with less than 0.7V dropout voltage?
3.3V 500mA is needed (STM32 Cortex M0 + wiznet w5500 + some leds...). Efficiency is not a problem (AC power)
I will take diode voltage drop as the simplest solution versus cost.