Off Board Power - How best to handle it?

Thread Starter

matthej

Joined Oct 10, 2020
52
Hi,

For my board I will be getting a +/-12V and +5V from another board (power board). At this time, I do not know much about this power.

How do people usually handle these voltages when they come on the board?

I plan on using DC-DC converters for the 5V, but can use the +12 and -12V directly.

Will a simple filter do? What questions can I ask about regarding the delivered power (noise etc)?

Thanks!
 

dl324

Joined Mar 30, 2015
13,124
I plan on using DC-DC converters for the 5V, but can use the +12 and -12V directly.
If the other board supplies 5V, why do you want to generate your own?

What type of circuitry (audio, logic,, other analog)? How much current from the 5V supply?
 

Thread Starter

matthej

Joined Oct 10, 2020
52
If the other board supplies 5V, why do you want to generate your own?

What type of circuitry (audio, logic,, other analog)? How much current from the 5V supply?
So it is a mix of analog and digital circuitry. The analog needs +/12V for the most part. The digital needs 3.3, 2.5, 1.8, so I was going to use the +5V supply to generate these circuits from a dc-dc converter.
I was checking to see if I have to do any special with the 12V before I use it directly with my analog circuits (filter?)
 

dl324

Joined Mar 30, 2015
13,124
I was checking to see if I have to do any special with the 12V before I use it directly with my analog circuits (filter?)
Before we can give any intelligent answers, we need to see a schematic, any noise complaints/concerns you might have, and the currents required from each of the supplies you intend to generate.

I've had analog circuits that were affected by 150mV of supply noise, but only when outputs were swinging close to the supply. Don't recall any digital circuits (5V) having issues with that amount of ripple. Can't do any more experiments because I finally got around to fixing the power supply issue that was causing excessive ripple. I thought it was a design flaw, but when I looked at the circuit, it turned out to be a bad cap.
 
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