ADS131M08: Can ADS131M08 be use for single-end input signal?

Kazuya-san,

Yes, the ADS131M08 can be used for a single-ended input measurement with the negative input pin tied to ground. For this type of information, you would look at the Recommended Operating Conditions table on page 5 of the datasheet. Here is the section for analog inputs:

This device has a negative charge pump that allows for input signals that go as low as 1.3V below ground. However, you can operate this device with the inputs going only from 0V to VREF. I would note that the ADCs are fully differential, so if the inputs are only positive values, then you would only get output data from 000000h to 7FFFFFh, which would be equivalent to 23 bits.

Joseph Wu

Kazuya-san,

I still think that the ADS131M08 is your best option. It has all of the functions you list, except for the 24-bit data length in single-ended measurement operation.

I would point out that for 24-bit ADCs, the noise usually makes the performance about 20 bits. To get to 24 bits of noise performance, you need a reference that has incredibly low noise, and you generally need to run the device at extremely slow speeds. If your customer needs all 24-bits, they can run the device at 2x the desired speed and average 2 samples to get 24 bits.

Out of curiosity, what is the application? This might help identify a different solution.

Joseph Wu

Kazuya-san,

The ADS1248 is a fine device, but it still has the same issue as the ADS131M08. The device uses a differential ADC and single-ended measurements (positive values) will still be reported with 23-bits. Additionally, when using the ADS1248 as a single supply (0 to 5V), the ground is not a valid input. Because the input has a PGA as a buffer, even in gain of 1, the lowest an input can go is 0.1V above the ground (AVSS). Lastly, there are 8 independent inputs that you can select as differential measurements for the ADC. That means that you would select one of them as the negative inputs and the remainder would be the measurements. In the end, you could only measure 7 single-ended inputs.

One possible device you could recommend would be the ADS1263. It is a 32-bit ADC with multiple channels. Again, I think that the ADS131M08 would likely work in your customer's application, but I would need to know more about it.

Joseph Wu