24 Bit, dual channelADC, SPI Slave, 85 DegC (or more)

There are a number of things you need to watch out for, in addition to the temperature specification:

Very few ADCs will give you 24 bits of noise free data at 480 samples/s.

multi-channel Delta-sigma ADCs often incur a significant timing penalty when switching between channels. To collect two channels at

480samples/s you may actually have to use a sampling rate 3 to 5 times higher to allow the internal digital filters to settle after switching the multiplexer.

Your best bet might be to use two separate ADCs such as the CS5532. That would allow you to avoid the timing penalty incurred when switching channels.

Mark Borgerson

st be

TI shows 42 candidates on their selection guide, and this one sounds a good fit

[" * Available in Extreme (=9655=B0C/210=B0C) Temperature Range(1) # APPLICATIONS * Down-Hole Drilling "] bingo!

-jg

TI shows 42 candidates on their selection guide, and this one sounds a good fit

[" * Available in Extreme (?55°C/210°C) Temperature Range(1) # APPLICATIONS * Down-Hole Drilling "] bingo!

-jg

Thanks for this. Looks good (low power, good temperature range). Bill

Hmmm, they seem to draw 500 mW (max) each! Also temperature range limited to -40°C to +85°C. Still, I will point this device out.

Still, very interesting.

I've looked at how much time jitter is allowed to avoid disturbing LSB with maximum swing. It's not very much! Perhaps the application really calls for 17 bits. Still, I am only a programmer :-)

Bill

Yowza. TI's listing them at $125 by the 100 for just the standard mil-temp rated parts. Let me tell you how glad I am to not need down-hole temperature ratings on any of my designs.

--=20 Rob Gaddi, Highland Technology Email address is currently out of order

Nah, that price is specifically for the -HT high temperature versions. The military temp parts are the ADS1278 (without the HT), and are about $25.

Anyway, that's nothing compared to the space-rated parts. It can't be cheap building a satellite...

I successfully used "S" version Analog Devices AD7713's 20 years ago in geothermal downhole tools at 100 deg C.

On Oct 1, 3:49=A0am, Rob Gaddi >

That may be eye-watering, but it's still WAY cheaper than replacing one that failed!! - in the scheme of "need a sensor down a hot hole", it really is relatively cheap :)

-jg