I've been reviewing the datasheets for two 24 bit delta-sigma ADCs and I'm trying to determine which one is better for my application. I understand that PCB layout is very important for 24 bit data converters however and can be a pain, but when the 16 bit variants of these chips are only about $1 less it' s hard not to use the 24 bit chip :). The chips I'm looking at are:
Both are roughly the same cost at $12 - $13 each for single buys.
I'm trying to make a data logger for various sensors (bridge sensors, thermocouples, etc.) so the more channels I can get per chip, the better. The AD7794 has 6 differential channels while the ADS1232 has 2 differential channels. Both chips also have programmable gain amplifiers however, the AD7794 has more programmable gain levels (1, 2, 4, 8, 16, 32, 64, 128) than the ADS1232 (1, 2, 64, 128). From what I can tell, using an external reference at the same sampling speed, the noise/effective bits are similar between the chips (the max sample rate on the AD7794 is much higher at 470 compared to the ADS1232's 80). Finally it appears that both have an on-board temp sensor (i.e. for thermocouple cold junction measurements I assume), but the AD7794 seems to have very little discussion on it.
Is the AD7794 clearly better or is there some key feature(s) I'm overlooking? Any thoughts on which one would be better would be helpful.
You have to start with a list of what's important to you. Accuracy? precision? power consumption? number of channels?
For a $12 A/D converter you could spend an entire day laying out the parameters side by side and constructing a decision matrix, but first you have to prioritize. On the face of it, I'd say the the AD7794 is the better part because:
It has more channels
It is from Analog Devices (and it don't get no better than that)
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons
Thanks for the quick reply Rugged Circuits. I'd say the number of channels per IC matters the most as interfacing a multiplexer on a separate IC will likely add a lot more noise than an integrated one. As far as power consumption goes, I'm looking at using an SD card, so the amount of power the ICs use isn't too much of a concern. As far as accuracy goes, I'm just looking for something with higher than 16 bit or higher accuracy. Basically I'm looking for a complete front end with a PGA, multiplexer, temp sensor, all in one chip.
In general, are AD chips typically better than TI chips?
