ADGM1004 All inputs Grounded

Help! We've implemented ADGM1004, but we seem to have all RF paths grounded. We believe we're blowing the part as soon as we power up , but we are unsure why. Below is our schematic. WE've verified that VOUT_Cntl1 is at 3.3V and pins 20,18,12,10 are showing up as ground.

Thanks!

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    •  Analog Employees 
    on May 11, 2021 9:20 PM in reply to aaronf30

    Hi Aron, 

    I will try and help you.  Looking at your connections they look fine.  The drive seems to be operating as you see the voltage at C2.  All good.  Can you check that you are drawing around 2mA from the Vdd supply as well.  The external 10M shunts will mitigate any floating issues on the RF pins if there are not other terminations, great.  Looks like all your grounds are common which is good, is the digital ground common to the RF ground?  You say the RF pins are showing up as ground.  Are you measuring the Resistance between RFC and RF1, 2, 3, 4 as an open circuit or low impedance?  What is the Switch channel resistance showing up on using a DMM? Open?  Does it change when you change the logic control voltages?  

    Eric.

  • Thanks for your reply.

    unfortunately 2mA will be hard to determine, there are a lot of 3.3 volt devices on the line.  All grounds are common. 

    Actually i miswrote, all the resistances between RF1,2,3,4 and RC are about 3 ohms. We can not get any connections to be open.  When we change IN1 from 3.3V to 0 , all connections remain closed.

  • 0
    •  Analog Employees 
    on May 12, 2021 10:56 AM in reply to aaronf30

    Hi Aron,

    ok, so we are in a permanently on state.  Is this the case even when you disconnect Vdd?  i.e. have the part unpowered completely? If you un power the part all switches should open (normally open).  Do you see the channels on even before you have cycled the logic control lines for the very 1st time?  Usually if the part is stuck on then its likely there was some kind of hot switching that has ended up damaging the contacts and sticking them on.  Its strange though as you have all the RF pins grounded so even if you accidentally toggle the switch there should be no power going through them.  Is there a chance that their maybe charge building up during assembly and toggling happing then?  This part has ESD protection diodes that give 5kV production on the RF pins for HBM and 1.25kV FICDM, so you should be ok there w.r.t. ESD.  

  • We checked and when we turn the 3.3V line off, the connections are all open. the reason all pins is are gounded when we turn 3.3V line is RF4 is grounded through 50Ohms As soon as we power it on all connections close.

  • Hi Eric, 

    We think we solved it. We were doing something stupid on the control lines.. We jadded pull down resistors to lines and it solved out issue. Thanks for you assistance