Drew: Here are my part search notes, May 2008. (Note, I think analog mux plus on-board ADC's might be a better option)
Digikey, in-stock search, Package with 64-128 pins, reveals three ADC manufacturers:
1. Analog Devices
http://www.analog.com/dynamic/parametric/scResultsDisplay.asp?SearchType=PSS&ProductLine=ADC
AD7490. 16 inputs, 12 bit, 1 MSPS. Ser, SPI, $6 in quantity of 1000
28-TSSOP. $11.66 at Digikey
1MSPS is for 5V and 20Mhz clock. Nice coincidince!
SEXY, but has a lot of features to learn, although some seem ignorable, i.e. default control register settings.
2. Texas Instruments
TLC545, 19 inputs, 8 bit, 76KSPS. 28PDIP or 28PLCC. $3.85 in qty. of 100. Non-stock at Digikey
ADS1258. 16 inputs, 24 bit, 125KSPS 48QFN $10 in quantity of 100. Dual Supply. $14.58 at Digikey
Too scary. Too many pins, too nasty a package, too many bits of precision, too expensive.
3. National Semiconductor
www.national.com
ADC0816. 16 inputs, 8 bit, 10 KSPS. Parallel, ($9, $5), 40-DIP! Big Ass Chip! $13 at Digikey
ADC0817. Same as ADC0816. $9.11 (1/2 bit less resolution)
Older chip, 1/10 as fast as the AD7490, with four less bits of precision. For about the same price.
