Hi,
The AFE5818 is suggested to turn on according to the power supply sequencing by providing DVDD_1P2 before powering up the AVDD_1P8 rails.
But I am not able to find any provision for power sequencing on the AFE5818 Evaluation Board, still the AFE works fine.
So in our schematic design is it necessary to take care AFE5818 power sequencing or can we power all voltage rail at the same time?
Thanks in advance
DEEPAK V
Hi Deepak,
The AFE5818EVM actually implements power sequencing--it's just a little hidden. If you look at Page 2 of the board schematic, you'll see that different versions of the TPS796 are used for the DVDD_1.2 (adjustable Vout) and DVDD_1.8 (fixed Vout) supplies.
Pages 11 and 15 of the TPS796 datasheet mention that putting a bypass capacitor on the NR pin(fixed version) causes a delay due to the RC time constant formed by the internal 250kohm resistor and the bypass capacitor. This leads to an ~500us delay as measured on one of our lab boards below--which is well within the t2 range on Page 116 of the AFE5818 datasheet.
We recommend sequencing the power rails as specified in the datasheet.
Sincerely,
Olu
