Which LDO is the AD8422 suitable for?

Question

I have an AD8422 instrumentation amplifier. I need a +-5V source to supply the AD8422 instrumentation amplifier. 
 I am using ADR4550 as reference voltage. (1.) I already have the ADR4550 as a reference voltage do I still need an LDO? (2.) Excuse me, how do I generate +-5V to power the AD8422 instrumentation amplifier?Is it to use two LDOs or ADR4550s and reverse the +- pins of one of them? 
 By the way, my signal V+ is 2.2V, V- is 1.4V, after 10 times the output is +-4V? 
 
 Thanks Reply

kristinehoffman · Accepted Answer

Hi yaro-0916, 
 Thank you for the clarification! 
 ADR4550 only outputs +5V. If your region of operation would be +/-5V, yes you would need an LDO to supply the -5V. You can consult the Power Management Community for the best generic for this application. 
 To obtain a +/-5V output, refer to the transfer function below: 
 
 For an output of 5Vpk, with 2.2V and 1.4V input, you can try to configure your gain to 6.25 as per the Vout transfer function. Based on the G formula, your Rg should be 3.7kOhm to have a gain of 6.25. Another thing to note is that is your ref is 5V, this would saturate your output. Try setting the ref to <2.5V and >-2.5V. Lastly, AD8422 has an output swing limitation of as seen below: 
 
 You should raise your supply rails to compensate the output swing of AD8422. 
 Hope this helps! 
 Kristine)

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Which LDO is the AD8422 suitable for?