[time-nuts] Low noise power supply

David VanHorn D.VanHorn at elec-solutions.com
Wed Mar 9 11:20:26 EST 2011


Granted my case wasn't a GPS app, and I didn't have sufficient test equipment to properly document the noise level of the final solution, but it made a huge improvement in picture quality relative to the SMPS alone, and I routinely design very quiet switchers. In this particular application, a linear only solution was not an option. The system ran on three 123A cells for about 20 mins, with four of these imagers talking 27 MHz LVDS, a good sized FPGA, a fast processor running linux, high power Wifi, GPS receiver (antenova), and a suite of other sensors. The processor core alone ran six SMPSs.  Without good layout, the thing would have been an EMI nightmare.

The point of the 9000 was that it's CMRR is large, and I was able to put the SMPS feeding it in the "sweet spot" where the 9000 has best PSRR. That still requires high attention to current paths in layout but the result was very very good. Near starlight image capture where the factory recommended approach gave us nothing but noise at low light levels.




-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of ehydra
Sent: Wednesday, March 09, 2011 8:11 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Low noise power supply

For me, this looks like a advertisement campaign only. Not very 
sophisticated or ingenious. Read that you don't need LC-filters at the 
output because of the LDOs. *lol* If the designer ever heard of corner 
frequency??
And the ISL9000A is the same.


- Henry

-- 
ehydra.dyndns.info


David C. Partridge schrieb:
> Hmmmm I wasn't impressed.  The 'scope screen shot of noise levels on the outputs used 20mV/division, and the thickness of the regulated traces told us precisely nothing.  Now if the author had measured 20uV noise over a BW of 10Hz to 100kHz (about 63nV/rtHz), or 3uV over the same BW (about 10nV/rtHz), I'd have started to get interested.  
> 
> However as no claims were made, I took the title of "Ultra-Low Noise" with a large shovel of salt.   
> 
> 
> Regards,
> David Partridge
> 
> 
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of EWKehren at aol.com
> Sent: 08 March 2011 21:41
> 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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