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AD7195 12bits on a shorted input?

Question asked by cydrollinger on Nov 7, 2014
Latest reply on Nov 24, 2014 by jcolao

My inquiry is about getting nearer to 24bits of resolution when the inputs of the front end of the AD7195 are shorted (AIN1 and AIN2). The device is in a default state as none of the registers have been written to, but they have all been read: Status:0x0, Mode:0x80060, Configuration: 0x117, Data: 0x7ffbda, ID: 0xa6, GPOCON: 0x2, Offset: 0x800000, FullScale: 553a40. The front end consists of a differential pair, with adjustable collector current, driving an AD8475.  With a little effort I am unable to measure a differential voltage at the input into the AD7195. The differential pair is sourced by the same voltage regulators as the AD7195.

Attached is a image of the schematic, AFE.png.

Any help to increase the SNR would be appreciated!




Cy Drollinger