DRS4 Forum
  DRS4 Discussion Forum  Not logged in ELOG logo
Entry  Thu Jun 20 01:36:48 2019, Andrew Peck, Evaluation firmware wait_vdd state 
    Reply  Fri Jun 21 12:54:47 2019, Stefan Ritt, Evaluation firmware wait_vdd state 
       Reply  Mon Jun 24 23:07:35 2019, Andrew Peck, Evaluation firmware wait_vdd state 
Message ID: 753     Entry time: Thu Jun 20 01:36:48 2019     Reply to this: 754
Author: Andrew Peck 
Subject: Evaluation firmware wait_vdd state 

Dear Stefan,

I am working with others at UCLA on a custom made board built around the DRS4. We are in the process of writing firmware so I am adapting the readout state machine from the evaluation board firmware.

I see in the state machine of the eval board firmware that after a trigger is received, the FPGA goes into the start readout state and then into "wait_vdd", where the FPGA waits "~120 us for vdd to stabilize" before reading out the ADC.

Our application is sensitive to deadtime and this wait_vdd state adds very significantly.  I am trying to find anything explaining the necessity of wait_vdd in the documentation / elog and have only found so far your old forum posting, https://elog.psi.ch/elogs/DRS4+Forum/12

Does this forum posting explain wait_vdd or is there a another purpose that I have missed?

If this post is relevant to wait_vdd, does the advice of large capacitance and an LDO with fast transient response still apply or are there any new recommendations?

Thank you,

Andrew Peck

ELOG V3.1.4-bcd7b50