Hi all,
The DG419L is a low voltage CMOS analog switch made by Vishay siliconix. Ca n V+ and V- be connected to VL and GND respectively, as from the data sheet it doesn't look immediately obvious....none of the app note circuits show them as connected. Hoping someone has already used the part, and come acros s this.
Cheers,
ozzy.
Not used it, but yes.
V- connected to GND is implied by the "single supply" specifications.
VL to V+ is actually shown as an example on some of the graphs, e.g. Switching Threshold vs Supply Voltage datasheet p7.
-- John Devereux
The data sheet should specify the voltage limits on V+ and V- relative to VL and GND. If those limits go to zero, then you can connect 'em up.
If you're going to be using that whole voltage range then pay attention to the performance of the switch close to the rails -- data sheets generally trumpet switch performance in GREAT BIG LETTERS in the center of the range where it's best, and leave it as an exercise to the user to figure out if it'll actually work where they need it to.
-- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Can V+ and V- be connected to VL and GND respectively, as from the data she et it doesn't look immediately obvious....none of the app note circuits sho w them as connected. Hoping someone has already used the part, and come acr oss this.
Thanks for setting me on the right direction (John, Tim). I wasn't aware t hat VL was switching threshold, but have it connected to supply voltage on my schematic. This was the only thing I'd left unanswered, and thought it best to check before going to PCB.
I was gonna go directly to Vishay but before they answer your questions, wa nt a company name etc....I'm working on this! Besides I nearly always get top answers from people here.
Cheers,
Ozzy.
Just a point of clarification - it is not the actual switching threshold, but it does control it. The idea is that in a mixed-signal system, it is connected to the "logic" supply rather than the "analog" supply. So you could have 3.3V logic operating the switches, but use
+/-5V supplies to the analog circuits and to the V+/V- of the DG419L.So for a 3.3V VL the actual switching threshold is about 1V, as per the graph.
(I have not actually used this chip, or read the datasheet exhaustively. But it is an extremely common arrangement for this sort of thing.)
-- John Devereux
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