We are using the AD7175-8 and have it mounted on a custom board, and we also on a EVAL board purchased from AD. We are using a 5V external reference voltage on our custom board, and the EVAL board also has an external 5V reference.
The data sheet states that the REF_SEL0 bits in SETUPCON0 can be written with '00' for use with an external reference and '10' for the internal reference of 2.5 V. The latter also requires the REF_EN bit in ADCMODE to be set to 1.
We are using an external power supply directly as a known input to AIN5 with no other inputs. On the eval board, we have removed LK8 and LK21 jumpers such that all inputs are shorted to one another but to no other source. We are configured for unipolar mode.
- When we supply 2.5 V as input and configure for external reference, we expect to see half counts, but are instead seeing full counts, on all inputs.
- When we configure for internal reference, we see half counts on all inputs, as expected for the external reference.
This is leading us to believe that the configuration bits for REF_SEL0 behave the opposite of how the device is spec'd in the data sheet. I could not find any errata sheet. Has this behavior been noted or observed anywhere else?
Updated the product number in the title from AD7175 to AD7175-8
[edited by: JEstayo at 1:14 PM (GMT -5) on 22 Jan 2024]