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, 25 Apr 2024 21:38:48 +0000 From: John Larkin Newsgroups: sci.electronics.design Subject: Re: PI3USB14-A dual 4>1 USB switch for analog Date: Thu, 25 Apr 2024 14:36:57 -0700 Organization: Highland Tech Reply-To: xx@yy.com Message-ID: References: X-Newsreader: Forte Agent 3.1/32.783 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 55 X-Trace: sv3-zuLcHQcXt/ey8PcxFr+qogwxwGfQkV2iUK7qz+tfoqmTiNetf+9Ouq1QH53MMIEWoNWnKBt2mYbCmVe!cvuYtJS7XIAPeKBemEOIFWsDXXVSh3te8HRo9tY3w4T+9mPhPH+kd7dFN/lt7WlcoS8xJ0ksUFrj!0p1BmA== 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: 3526 On Thu, 25 Apr 2024 12:28:42 -0400, Phil Hobbs wrote: >Hi, all, > >I'm in a bit of a rush, doing revs to a testing board for a prototype >lidar ASIC that turns out to be..., um..., well.... Let's just say it's >a _tiny_bit_delicate_ electrically. Yeah, just a little delicate, >that's it. (Not our design or our nickel, fortunately.) > >It runs on a single supply, so the only sequencing issues are with the >signal pins. Thus the test board is going to bring up V_DD smoothly and >not too slowly: a monotonic edge of about 100 us. While that's going >on, all the inputs and outputs will see 100k ohms to ground. (All the >enables are positive-true, which makes this easier.) > >The digital pins are all inputs, so they're just buffered with >SN74LVC1G125s (tri-state Schmitt noninverting), with the aforementioned >100k to ground on their outputs. > >The analog outputs don't have much drive, but can go pretty fast if you >keep the capacitance down. There are a fair few of them, so I want to >mux them down before the op amp buffers (OPA2626es--surprisingly nice >chips). > >Because we're not made of money, and the test boards aren't ITAR, we're >getting them made and stuffed at JLCPCB. Thus we care a lot about what >their tame distributor LCSC has in stock. > >They're fairly light on analog muxes, it turns out. Going through what >they do have, I was reminded just how awful the capacitance of old-timey >mux parts is--way over 100 pF at the common pin of an 8-1, blech. > >They do have these very nice-looking USB switches, type PI3USB14-A, for >pretty cheap ($0.45 @ 1ea) and in plentiful stock. > >They look beautiful--6 ohms R_on, 4 pF C_off typical--but apart from one >crosstalk number, the datasheet gives only sketchy hints about their >actual analog performance--bandwidth and crosstalk, but nothing about >charge injection, switching times, make-before-break, resistance >linearity, or distortion. > >Has any of you used them for actual analog stuff? > >Thanks > >Phil Hobbs We use TS3USB30EDGSR to switch/mux fast signals. We mostly use them as setup-time switches, things like polarity switching and low/50r source impedances, things like that, so we haven't explored dynamics much. They do propagate fast signals nicely. How about using relays?