I have to design a circuit with a ad8221 Instrumentation amplifier which is supplied from +/- 15V.

however the only supplies i have on the board are 5v and -5v. i have looked at DC-DC converters to boast the voltage up to +/- 15V, however i am aware that DC-DC converters can be noisey and might be to noisey for a IA.
would any one be able to recommended a low noise DC-DC converter or better still a better idea of creating the +/- 15v from +/-5v.

thanks

Mark

 

Maybe a little LC low pass filter on the supply to knock down the switching frequency.

 

The AD8221 will work from ±5V supplies.

 

Thanks for the replies, the signal going into the IA is from 0v to around 12v so i need the higher voltage. the set up is 0-12v varying voltage into the IA then into a an adc then fpga and also also from the IA to a fast comparator which will create a ttl pulse

 

So I see two choices:

Use a DC-DC inverter with a careful layout using a ground plane and a lot of filtering to minimize the noise.

Reduce the 12V input voltage with a resistive divider to the maximum input the IA can linearly handle.
(Why do you need an IA amplifier for a 0-12V signal?)

 

How often is the A/D converter being triggered, and how long does a conversion take? If the duty cycle is low, like an a/d conversion time of 10 us and a sample rate of 10 samples per second, you can use the signal that starts a conversion to shut down the dc/dc converters and restart them when the conversion is complete. That way the DC/DC converters are not running when the signal is being sampled and converted. Makes for a super low noise power system when it counts.

Old analog trick from old analog kid.

ak

 

How often is the A/D converter being triggered, and how long does a conversion take? If the duty cycle is low, like an a/d conversion time of 10 us and a sample rate of 10 samples per second, you can use the signal that starts a conversion to shut down the dc/dc converters and restart them when the conversion is complete. That way the DC/DC converters are not running when the signal is being sampled and converted. Makes for a super low noise power system when it counts.

Old analog trick from old analog kid.

That is a good trick.
A similar technique is to synchronize the A/D sample so it occurs just before the next dc/dc converter transition. But, of course, that requires some way to detect the dc/dc converter switching frequency.