[SI-LIST] Re: Mixed digital/RF board with switching power supplies

  • From: "J.D. Bakker" <jdb@xxxxxxxxxxxx>
  • To: matusov@xxxxxxxxxxxx
  • Date: Fri, 6 Jul 2007 22:18:43 +0200

Linear Technology have an interesting appnote:

http://www.linear.com/pc/downloadDocument.do?id=4159

In this document, Linear Technology's Application Note 70, a 
switchmode power supply design is presented with less than 100uV 
output noise, and little RFI. This is achieved by using a switch 
controller which has controlled output switch slewing, allowing a 
trade-off between EMI/RFI and efficiency. Methods to measure and 
control PSU noise are also discussed (IMHO, the EMI sniffer probe in 
Section J is particularly interesting).

An additional measure you could implement is to synchronize the 
switchers, and shift the switching overtones away from your frequency 
of interest.

Good luck,

JDB.
[not associated with LT in any way other than having used these chips 
in very low noise portable digital audio recorders]
-- 
LART. 250 MIPS under one Watt. Free hardware design files.
http://www.lartmaker.nl/
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