Electronic – How to obtain a dual power supply ±2.5V from a battery for a portable system

batteriesdualpowerpower supply

I’m working on a portable system that uses a microcontroller and an analog/digital converter. I want use this ADC in dual power supply mode so I need a ±2.5V .

In my previous project, the system was wire-powered by USB and made use of an isolated dual output DC/DC converter which provides a ±3.3V, so with two LDO positive and negative regulator I obtained the ±2.5V.

Now I want to transfer the project in a portable contest and I need to make some changes to reduce the system size. For this reason, I can’t use the previous DC/DC converter type yet cause they are too big for my intent.

I tried to find on the web distributors some IC that provide a dual ±2.5V power supply from a single positive source, but I found one or two solutions that don’t satisfy me at all. Furthermore, these IC use a charge pump that create on the output a very high ripple, but I think that if I use two LDO regulator with high PSRR the problem is in part solved.

So, my questions for you are:

  • Do you have any suggestion to obtain a dual power supply ±2.5V from a battery, with the noise as low as possible?

  • Do you know some good IC that made this?

Thanks in advance.

Best Answer

I came across the same problem when I looked into a similar ADC with +/- 2.5V supply. So I checked the evaluation kit they were providing: ADS131A04 Evaluation kit (power shematic p.29)

Apparently, they are doing the following:

  • +2.5V generated by LDO from the main power (5V from USB I think): U34
  • Charge pump used to generate negative voltage from the main power: U36
  • -2.5V generated by another LDO from that negative voltage: U37

ADS131A04 evaluation kit power supply

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