Path: ...!Xl.tags.giganews.com!local-1.nntp.ord.giganews.com!news.giganews.com.POSTED!not-for-mail
NNTP-Posting-Date: Thu, 18 Apr 2024 17:16:05 +0000
From: Joe Gwinn <joegwinn@comcast.net>
Newsgroups: sci.electronics.design
Subject: Re: spread-spectrum model
Date: Thu, 18 Apr 2024 13:16:04 -0400
Message-ID: <7qk22jlrrc9949ccrkdk058b4dinnnt75f@4ax.com>
References: <v9e22jtqn47cl4t956nub9dbqnm5qepkl1@4ax.com>
User-Agent: ForteAgent/8.00.32.1272
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Lines: 48
X-Usenet-Provider: http://www.giganews.com
X-Trace: sv3-LGY5OGGI4qY7lc816e8885GsAUOQLRAkaHUZyO7jq9BJ8LP4qulHC8h5UWuOaYRaPKAQ2aHY26Uy8WD!0QYk3keCRxBT0yr8yh7eyZuIBVGiVZYVHTK3jeIxjBy9cejKN/o+YotVTgjBehEQwR1cajM=
X-Complaints-To: abuse@giganews.com
X-DMCA-Notifications: http://www.giganews.com/info/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: 2539

On Thu, 18 Apr 2024 08:26:56 -0700, John Larkin
<jjSNIPlarkin@highNONOlandtechnology.com> wrote:

>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.

I'd check for cross-correlation as well, so no ganging up in systems
using multiple channels in some signal path.

Depending on details, the problem could manifest itself as peaks or
ripples in the time domain, your beloved homeland.

Joe Gwinn


>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