I have made a circuit based on the FT232R data sheet example "Figure 6.3 Bus Powered with Power Switching Configuration". Basicly it uses a IRLML6402 (P-Channel MOSFET) tp power up the rest of the circuit once the FT232R has request > 100mA current.
The voltage drop over the IRLML6402 is 0.5V, I really require a voltage drop of 0.25V or less. There must be a better alternative to this? 0.5V seems higher then what I expected from the IRLML6402 recommended by FTDI.
The circuit draws around 250mA and can also be self powered. I noticed that while in self powered mode, the the IRLML6402 doesn't seem to stop current going through the reverse direction back to the USB VCC. For some reason, I expected the MOSFET to act as a diode and stop current flowing back though to USB VCC when in self powered mode.
Any help or advice would be greatly appreciated.