JAJSGG2C October 2018 – June 2019 ADS125H02
The ADC requires three analog power supplies (high-voltage supplies HV_AVDD and HV_AVSS, and low-voltage AVDD) and a digital power supply (DVDD). The high-voltage analog power-supply configuration is either bipolar (±5 V to ±18 V) or unipolar (10 V to 36 V). The AVDD power supply is 5 V. The digital supply range is 2.7 V to 5.25 V. AVDD and DVDD can be tied together as long as the 5-V power supply is free from noise and glitches that can affect conversion results. An internal low-dropout regulator (LDO) powers the digital core from the DVDD power supply. DVDD is the digital I/O voltage. Keep in mind that the GPIOs are referenced to AVDD and AGND voltage potentials.
Voltage ripple produced by switch-mode power supplies can interfere with the ADC conversion accuracy. Use LDOs at the switching regulator output to reduce power-supply ripple.
Inrush current is drawn from AVDD when the internal reference is enabled as a result of charging the 10-µF REFOUT capacitor. Observe the AVDD voltage under this condition and verify the supply does not drop below 4.5 V.