Hi,
We are using six ADCs - ADS61B29IRGZR(ADC-14-/12-Bit, 250-MSPS ADCs With Integrated Analog Buffer from TI)in our design . Among them 5 are operating at 50 MHz clock and the other one at 200MHz.
The analog 3V3 power supply for ADC is provided by TPS7A4700 (1A Low-Drop-out Linear Regulator from TI) and the digital 1.8V power for ADC by TPS71718DCKT (Low-Noise, High-Bandwidth PSRR, Low-Dropout,150-mA fixed Linear Regulator from TI). Separate 1.8 and 3.3 regulators are present for all the ADCs and the 1.8 is derived from 3.3V of respective ADCs. All the 3.3V power regulators gets the input from external 5V input power .
All the 3.3V power is coming properly. For one of the 50 MHz ADC both 1.8V and 3.3V powers are coming proper. But for other ADC we are facing some issues for the 1.8V output. The voltage is rising to 1.96,2.01 and 3.1 for different regulators . when we are soldering similar circuit for TPS71718DCKT in a general purpose board(without load) we are observing the requires 1.8V output. But when the same circuit is coming to the PCB board and connected to ADC it is rising high as mentioned above.
Best Rgds,
Mahesh