I would like to convert 5V rail I have on PCB to ±12V. Existing solution is using boost converter 5V to 12V, and a buck for 5V to -12V. This feels bulky for what it's needed - here are the requirements:

• +12V and -12V rail shall serve for powering opamp only
• Ripple of the ±12V rails is not of a concern, as the opamp is used in comparator mode(something I would like to swap with the comparator in the future but keeping it for now in the design)
• +12V and -12V rail should be within ±5% ie. acceptable voltage range of rail is (11.4V, 12.6V) both for positive and negative
• ±12V rails shall be capable of providing no more than 5mA of current
• There is a 3V3 powered uC on board with available PWM output which could be used for charge pumps

Everything mentioned so far asks for a charge pump, the way how I see it.

Some options I found:

• Maxim/Analog have +5V to ±10V converter IC MAX680/681, with VCC max of 6.2V and V+/V- being +12V/-12V in absolute maximum ratings, I feel like stretching it + it is not within acceptable voltage range
• Do a DIY charge pump using PWM uC output - haven't done this earlier so if someone could explain a concept with jellybean components that would be a useful answer as well.
• Use a standalone 5V to ±12V converter like a Murata one
• Use 2x dedicated charge pumps - 5V to 12V(to be found) and 12V to -12V(TC1044S)

Questions:

• Could charge pump 5V to ±12V be implemented with 1xPWM output from the uC, how would the circuit look like and what would be the component values(capacitor size, diodes, etc.)?
• Are there some other way how to do this which I have not covered?

posted 12 months ago

CC BY-SA 4.0

12mo ago by Nick Alexeev‭

2kind‭

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