Hello,

I'm wanting to use the AD7780 in a non ratiometric configuration which means that Vref does not equal AVDD. Page 3 of the datasheet says that the Differential input Voltage Range = +/-Vref / gain when the assumption is that Vref = AVDD. Does this equation still apply in the configuration i want to use it?

AVDD = 5V

Voltage REFIN = 2.5V (REFIN+ = 2.5V, REFIN- = GND)

According to the equation above the input would be limited to 19.5mV differential input voltage at 128 gain. I'm wondering if the input range is actually defined by AVDD?

Thanks,

Kevin

Hi Kevin,

The input range is defined by Vref. So, with a 2.5V reference, the input range is +/-2.5V/gain which equals +/-19.5 mV. If you are using an absolute reference, a low-noise reference such as the ADR381/ADR391 should be used.

Regards,

Johnny