AD Converters with low voltage external reference.

[Bernd Felsche]

Jörgen Karlsson tapped away at the keyboard with:

> Does anyone know of a adc that can use an external reference with very low
> voltage, I have found units that can be used with a 1V reference but I would
> like to get down to 50-60mV. I am trying to limit the part count needed for
> type K thermocouples.

The Atmel 8-bit AVR RISC MPUs allow Aref as low as Agnd. Something
like an AT90S8535 has 8 analog channels and dozens of digital I/O to
drive displays, etc as well as heaps of other functions. Chip cost
is fairly low; you should be able to source one-offs at about US$20.

	http://www.atmel.com

It's fairly straight-forward to record values in the limited on-chip
RAM, or to hook up an external data-logger (PC or palmtop) via RS232
(UART on-chip), or the SPI. The ADC is a 10-bit process. The part is
typically rated at -40C to +85C.

There are smaller AVR processors with fewer I/O which might be
sufficient.

-- 
Bernd Felsche - Innovative Reckoning
Perth, Western Australia
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