ZHCSEJ3B June 2015 – April 2020 ADS131E08S
PRODUCTION DATA.
The analog inputs to the device connect directly to an integrated low-noise, low-drift, high input impedance, programmable gain amplifier. The amplifier is located following the individual channel multiplexer.
The ADS131E08S analog inputs are fully differential. The differential input voltage (VINxP – VINxN) can span from –VREF / gain to VREF / gain. See the Data Format section for an explanation of the correlation between the analog input and digital codes. There are two general methods of driving the ADS131E08S analog inputs: pseudo-differential or fully-differential, as shown in Figure 19, Figure 20, and Figure 21.
Hold the INxN pin at a common voltage, preferably at mid supply, to configure the fully differential input for a pseudo-differential signal. Swing the INxP pin around the common voltage –VREF / gain to VREF / gain and remain within the absolute maximum specifications. Verify that the differential signal at the minimum and maximum points meets the common-mode input specification discussed in the Input Common-Mode Range section.
Configure the signals at INxP and INxN to be 180° out-of-phase centered around a common voltage to use a fully-differential input method. Both the INxP and INxN inputs swing from the common voltage + ½ VREF / gain to the common voltage – ½ VREF / gain. The differential voltage at the maximum and minimum points is equal to –VREF / gain to VREF / gain. Use the ADS131E08S in a differential configuration to maximize the dynamic range of the data converter. For optimal performance, the common voltage is recommended to be set at the midpoint of the analog supplies [(AVDD + AVSS) / 2].
If any of the analog input channels are not used, then power-down these pins using register bits to conserve power. See the SPI Command Definitions section for more information on how to power-down individual channels. Tie any unused or powered down analog input pins directly to AVDD.