SBAS550C June 2011 – May 2015 ADS4229
PRODUCTION DATA.
The ADS4229 has two power supplies, one analog (AVDD) and one digital (DRVDD) supply. Both supplies have a nominal voltage of 1.8 V. The AVDD supply is noise sensitive and the digital supply is not.
For best performance the AVDD supply should be driven by a low noise linear regulator (LDO) and separated from the DRVDD supply. It is possible to have AVDD and DRVDD share a single supply but they should be isolated by a ferrite bead and bypass capacitors, in a PI-filter configuration, at a minimum. The digital noise will be concentrated at the sampling frequency and harmonics of the sampling frequency and could contain noise related to the sampled signal. While developing schematics, it is a good idea to leave extra placeholders for additional supply filtering.
For best performance the AVDD supply should be driven by a low noise linear regulator (LDO) and separated from the DRVDD supply. It is possible to have AVDD and DRVDD share a single supply but they should be isolated by a ferrite bead and bypass capacitors, in a PI-filter configuration, at a minimum. The digital noise will be concentrated at the sampling frequency and harmonics of the sampling frequency and could contain noise related to the sampled signal. While developing schematics, it is a good idea to leave extra placeholders for additional supply filtering.
Because the ADS4229 already includes internal decoupling, minimal external decoupling can be used without loss in performance. Note that decoupling capacitors can help filter external power-supply noise; thus, the optimum number of capacitors depends on the actual application. A 0.1-uF capacitor is recommended near each supply pin. The decoupling capacitors should be placed very close to the converter supply pins.