I'm currently working with a ADS8472EVM to evaluate the ADS8472 Digital-to-Analog converter for an Audio application.
When testing my application I noticed that the the ADC always measured half the applied voltage. After some searching I found that the reason for this is that the ADS8472 has an input resistance of 49.9 Ohms and as my signal generator has an output resistance of 50 Ohms thus forming a voltage divisor.
The input resistance of ca. 50Ohms is due to the fact that there are 50Ohm resistors on the board between IN+ / IN- and GND.
Can anybody explain me why there are 50 Ohm resistors on the board? In my opinion you generally want a high input resistance when measuring voltages.
--
In the Datasheet of the EVM board (http://www.ti.com/lit/ug/slau203/slau203.pdf) you can see the two resistors R2, R3 on page 17.
