[time-nuts] Low noise power supply

[David VanHorn]

I had this problem when using some ultra low light imagers.  They have NO PSRR, and the integration times were up in the 1-3 second range, so any noise on the pixel supply ended up in the image.

I used an ICL-9000 regulator which has ultra high PSRR, and I used a switcher running at a specific rate where the ICL-9000 has maximum PSRR.  I also was very concerned with waste power, so the SMPS was set up for the output to be just high enough for the linear to stay in regulation.  

For this app you'd want a beefier reg, but search for high PSRR at the right current range and work backward from there.

Layout is also HUGE in keeping switchers quiet.  Most of what I do has switchers in the 1-5W range, and I only use two layer boards, but I get my noise low enough that both the pre-scan with GTEM and OATS site can't see whether I'm on or off. (conducted or radiated thru 15 GHz)

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of EWKehren at aol.com
Sent: Tuesday, March 08, 2011 2:41 PM
To: time-nuts at febo.com
Subject: [time-nuts] Low noise power supply

There is an interesting article in the March 2011 Electronic Products  
magazine "design an ultra low noise supply for analog circuits. It is a  
combination of switcher and LDO's and written by P Hunter TI so it may also  be 
available on their site.
Bert Kehren 
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