Amy, Looking at the scope, it does look like there's some small movement on the DOUT line but that's very revealing. Normally, I might try to reflow the device on the board to see if there is a bad connection. Unfortunately, there aren't a lot of good or easy options to check the device. Almost everything requires the DOUT line to show that there's something happening with the device. At this point, it looks like DOUT might be stuck to VDD through a low impedance. I might try looking at the supply current if you have a series supply resistor. Or if you have a series input resistor, you could set the device to the smallest input range and see if you can measure the input current, to match the equivalent analog input impedance (differential) in the datasheet. If the input current is correct, it shows that the ADC is working and sampling the input. I might also visually inspect the boards to see if there's a bad connection elsewhere. I'd look at all the digital line traces from the ADC all the way back to the microcontoller (Incidentally, are all the DOUTs connected together? Or do they go to separate pins of the microcontroller? If they are separate pins, is the pin properly programmed as an input? If they are together, then there can't be a short to VDD or all devices would be stuck). Short of pulling up the device and replacing it with a new one, that's all I can think to recommend at this point. Joseph Wu
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