Does any ony know of a supply solution for +/-5 volt dual supply for noise sensitive ada4938 analog front end application?
Application includes 18 total ADA4938's that need+/-5V.
Any help is much appreciated.
Are you using 18 singles or 18 duals?
It looks like you need 40mAx18 (or 36) + load. If you are driving 200ohm loads that adds an additional 10-20mA per amplifier.
So your load current is in the order of 1-2A. You may possibly also be powering something else on that 5V rail?
The ADA4839 has great PSRR of 80dB up to 1Mhz and 60dB at 10Mhz, CMRR is also in that order of magnitude,
So depending on your signal levels and SNR/THD performance I would say your supply should be fairly quiet but since the amplifier has great PSRR you do not have to be overly concerned.
If you design a switching regulator you should be able to meet the noise profile of the power supply with a simple 2 stage filter (main LC + a bead and cap)
What supply voltages do you have available? 5.5V, 12V or something else?
For the positive supply I recommend the ADP2323 if you have 12V (it's a dual channel so you can use 1 channel to generate the 5V and the second to generate another supply for your system (like 3.3V or 1.8V).
For that use the ADP2323 Buck Regulator Design Tool to finalize the BOM
For the negative rail I would use a cuk configuration as it is the lowest noise option for negative supplies.
For that use the ADP1621 Cuk designer tool found here:
ADP1621 Cuk Design Tool and use the post filter option in the advanced settings.
Just to give you an idea of the performance level you can achieve directly from a switching regulator, look at the attached example, and I will be posting one based on the ADP2323 soon.
If you still feel uncomfortable with powering directly from a switcher you can always generate 6V and LDO to 5V with the ADP7104 (you may need a couple of those to split up the current into 500mA rails)
ADI Linear Regulator Design Tool and Parametric Search
WE have tested an alternative configuration called the SEPIC-CUK. This allows you to generate both the +5V and -5V but for the supplies to be well regulated the load needs to be even (which is the case in op-amp designs)
Here is the app note that goes with it: An Improved Topology for Creating Split Rails from a Single Input Voltage. This topology can be supported by the ADP1621 for the current levels you need.
I hope this helps,
Thanks very much for the help. Yes, Im in the 1-2 Amp range for load, and I have 12, 5, and 3.3 to source from.
The split rails using the ADP1621 seems like a good fit, I’ll take a look.
"Just to give you an idea of the performance level you can achieve directly from a switching regulator, look at the attached example, and I will be posting one based on the ADP2323 soon"
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