SLAS986D November 2014 – February 2018 AMC7836
The AMC7836 can support up to 16 bipolar analog inputs. The analog input range for these channels is –12.5 to 12.5 V. The bipolar signal is scaled internally through a resistor divider so that it maps to the native input range of the ADC (0 V to 2 × Vref). The input resistance of the scaling network is 175 kΩ.
The bipolar analog input conversion values are stored in straight binary format in the ADC data registers (address 0x20 through 0x49). The LSB (least-significant bit) size for these channels is 25 × Vref / 4096. With the internal reference equal to 2.5 V, the input voltage is calculated by Equation 1.
A typical application for the bipolar channels is monitoring of the 16 DAC outputs in the device. In this application the bipolar inputs can be driven directly. However, in applications where the signal source has high impedance, buffering the analog input is recommended. When driven from a low impedance source such as the AMC7836 DAC outputs, the network is designed to settle before the start of conversion. Additional impedance can affect the settling and divider accuracy of this network.