Requesting your engineering assistance for this problem.
I want to use USB or Li-Ion battery together with a dc/dc converter IC.
Output is 3.3V
Made a prototype today, works fine. 1uH inductor + 4.7uF ceramic caps.
I also want to use USB 5 volts. How can I do this?
One way of course is a diode from the battery, but 0.2 to 0.3V loss even with a good schottky.
Any idea how I can do this with a MOSFET or BJT (for instance BC327 PNP only drops 90mV)? And I only have N-channel digital MOSFETs here.
-When the battery is switched ON, and USB is connected, the battery should disconnect.
The dc/dc chip is started with a pushbutton, later this is turned off briefly with a microcontroller (2.2K pullup).
I want to use USB or Li-Ion battery together with a dc/dc converter IC.
Output is 3.3V
Made a prototype today, works fine. 1uH inductor + 4.7uF ceramic caps.
I also want to use USB 5 volts. How can I do this?
One way of course is a diode from the battery, but 0.2 to 0.3V loss even with a good schottky.
Any idea how I can do this with a MOSFET or BJT (for instance BC327 PNP only drops 90mV)? And I only have N-channel digital MOSFETs here.
-When the battery is switched ON, and USB is connected, the battery should disconnect.
The dc/dc chip is started with a pushbutton, later this is turned off briefly with a microcontroller (2.2K pullup).
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