Other Parts Discussed in Thread: ADS1255, ADS1261
We are using an ADC chip ADS1256 in our product, and now we have found an issue happened to about 10% of our prototypes, as described below:
In order to get good linearity, we used the 'buffer on' function inside the chip. For the issue prototypes, when the input voltage exceeds AVDD - 2 V, the ADC output will fiercely drop and then lock up.
For example, the power supply is 5V,
When the input is 3V, the reading is ~ 5100000
When the input signal rises to 3.7V, the reading is ~ 6260000
When the input signal rises to 3.8V, the reading is ~ 3230000
When the input signal rises to 4V, the reading is ~ 3230000
For higher input voltages, the ADC reading is kept near 3230000, with little change.
This phenomenon only occurs on ~10% prototypes. For the rest prototypes, when the input exceeds 3.7V, the ADC reading will be kept as the saturated reading as ~6400000.
We have two questions:
1. Is there a way, such as some special registers configuration, to ensure that the ADC output saturated value when input voltage exceeds the threshold and 'buffer on' is enable?
2. For those ADCs that do not have this issue in our factory now, will this problem occur on the client side due to environmental factors and aging after leaving the factory?
Thank you very much!