Path: Xl.tags.giganews.com!local-2.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Thu, 18 Apr 2024 15:28:40 +0000 From: John Larkin Newsgroups: sci.electronics.design Subject: spread-spectrum model Date: Thu, 18 Apr 2024 08:26:56 -0700 Organization: Highland Tech Reply-To: xx@yy.com Message-ID: X-Newsreader: Forte Agent 3.1/32.783 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 38 X-Trace: sv3-60GW5uXyvQCTyqepX1rTP4d85MJzxVAWBb8OTLFtKuk6IjjH7XxFeD63MBb1gnhyRHBjMSYLEN+2dsM!xZkmqcLqGiAZDNVn+eR8ILkwAXo/U7sfWBqWhAXu860jWTPvKxGuZDUqarQlPaELA6UCErBD17A5!7C/HIg== X-Complaints-To: www.supernews.com/docs/abuse.html X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Bytes: 2159 I'm designing a switching power supply module and could reduce EMI by going spread-spectrum on the switching frequency. The simple one below reduces things by 20 dB. Probe the SS node and FFT. The ss inside switching reg chips is no doubt more sophisticated. In an FPGA, we could do some sort of pseudo-random thing. On a multi-channel power supply, there may be some small advantage to have a separate spread per channel. That would be easy. Version 4 SHEET 1 880 680 WIRE 144 80 80 80 WIRE 240 80 144 80 WIRE 80 112 80 80 WIRE 432 112 384 112 WIRE 464 112 432 112 WIRE 80 224 80 192 FLAG 80 224 0 FLAG 144 80 MOD FLAG 432 112 SS SYMBOL voltage 80 96 R0 WINDOW 0 43 80 Left 2 WINDOW 3 12 111 Left 2 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value PULSE(0 1 0 1m 1u 1u 1m) SYMBOL SpecialFunctions\\modulate 240 80 R0 WINDOW 0 48 -48 Left 2 SYMATTR InstName A1 SYMATTR SpiceLine mark=220K space=280K TEXT 462 54 Left 2 !.tran 2m TEXT 400 144 Left 2 ;Basic spread-spectrum TEXT 408 176 Left 2 ;for P943 8-ch supply TEXT 432 208 Left 2 ;JL Apr 18 2024