I'm looking for a sigma delta 3.5 digit display-type A/D converter with display hold and on-chip LED drivers. Something like the MAX1496EPI seems nearly ideal, but I can't find a vendor for it, and am hesitant to commit to a part which may not be available in small quantities later. The alternative, I suppose, is to use a dual-slope converter like the ICL7135, and just bite the bullet as regards board real estate and other problems.
A/D converter
Apr 09, 2008
9 Replies
Maxim sell the chip direct on their website in small QTY, and have stock. Digikey and Newark have it listed, but no stock.
Dave.
Maxim makes an ICL7135 in a SSOP package
http://pdfserv.maxim-ic.com/package_dwgs/21-0056.PDF
but they\'re a little pricey:
https://shop.maxim-ic.com/storefront/priceavailable.do?Partnumber=ICL7135CAI&event=PartSearch&menuitem=PriceAndAvailability
JF
formatting link
- The 7107 has no provision for display hold. The 7117 does, but is hard to find these days, and will become more so. As to the MAX1496, they apparently have a stock of around 100, and once those are gone, it will be more than 6 months before they crank out another batch. Obviously not a hot seller, so maybe a prime candidate for obsolescence.
AFAIK all Maxim parts are equally "obsolescent". It's been a while since I asked, but when I did Maxim sales people would say "oh, we never obsolete anything". Experience says that's because Maxim never takes anything out of their line -- they just wait longer and longer intervals between actually making any.
Design in Maxim parts as a last resort.
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com
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1/ ICL7135 or equivalent = more than $5 per 1000 2/ Microcontroller with 12 bit ADC = around $1 (for example a MC9S08QE8 is around $1,2 per 1k), and you can add a couple of 0,01$ transistors if you need a LED display.Don't ask why these dedicated chips are nearly obsolete, no ?
Cheers, Robert
Maxim has obsoleted parts in the past. I was a recipient of them canning the MAX439, a really nice opamp, because they couldn't make it work on a new fab line. The designer of the part took off to the Himalayas never to be heard from again. Linear Tech was very happy to pick up the $50k/yr in business. Maxim took down their letter from the president on their web site a few years ago with the "never have obsoleted a part" statement after I pointed out that fiasco.
The more popular ones are still made in the millions for cheap DVMs and panel meters (hard to meet the high impedance input and reference input requirements with a delta-sigma), but they don't generally feature display hold. I wonder if freezing the RC clock on a 7107 (static display drive) with a BJT would work for him.
Best regards, Spehro Pefhany
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- Nope. You get a random collection of segments, and it behaves badly on restart. No matter, I've decided to go with the ICL7135 anyway, which has at least two second sources. Also, I've thought of a nifty use for the "underrange" output, which will save me a couple of comparators. Screw Maxim.
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