DRS4 Forum
  DRS4 Discussion Forum  Not logged in ELOG logo
Entry  Fri Feb 26 17:05:26 2021, Tom Schneider, Trouble getting PLL to lock 
    Reply  Fri Feb 26 17:59:14 2021, Stefan Ritt, Trouble getting PLL to lock 
       Reply  Fri Feb 26 18:33:52 2021, Tom Schneider, Trouble getting PLL to lock 
          Reply  Fri Feb 26 20:32:25 2021, Stefan Ritt, Trouble getting PLL to lock 
             Reply  Fri Feb 26 21:24:39 2021, Tom Schneider, Trouble getting PLL to lock 
                Reply  Fri Feb 26 22:12:58 2021, Stefan Ritt, Trouble getting PLL to lock 
                   Reply  Fri Feb 26 22:52:13 2021, Tom Schneider, Trouble getting PLL to lock 
                      Reply  Thu Mar 4 21:36:14 2021, Tom Schneider, Trouble getting PLL to lock 
                         Reply  Fri Mar 5 09:39:42 2021, Stefan Ritt, Trouble getting PLL to lock 
Message ID: 811     Entry time: Fri Feb 26 17:05:26 2021     Reply to this: 812
Author: Tom Schneider 
Subject: Trouble getting PLL to lock 

Hello,

I am working on a custom PCB design with the DRS4 chip, and I can't get the PLL to lock.  I'm feeding CLKIN with a 1MHz CMOS clock (REFCLK- tied to VDD/2), and I'm using the same loop filter as the eval board.  I see from the datasheet that the PLL is enabled by default, so I'm not writing anything to the config register on startup.  I am just driving DENABLE high approx. 100ms after startup and looking for the PLL lock bit to go high.  When I look at DTAP, I see a 3MHz signal.  Can anyone tell me what I'm doing wrong?

-Tom

ELOG V3.1.4-80633ba