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Discharging Routine

Question asked by cao001 on Apr 27, 2012
Latest reply on Jun 14, 2012 by Jon_oc

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Im having issue with discharge routine , it fail but doesn't show which "node" was not discharged properly only shows "board not tested".
the failures report is working properly for shorts, analog, digital....etc,

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Jon_oc May 1, 2012 5:22 AM
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Hi,

you can find a very nice detail about discharge routine in this application note, also you can look for 'discharge' in the manuals

http://www.home.agilent.com/upload/cmc_upload/All/EPT_HP3070_analog_discharge.pdf

of course, there is probably a timeout on your discharge - which means that during power on , the board is retaining current that cannot be discahrged , usual cause is large capacitors on power nets - something in mF range perhaps.

check that you have the correct board voltage specified and also the correct parallel capacitance total for each net correct defined in the .discharge file

for very large capacitors, sometimes you have to use a gp relay to connect a resistor across to fully discharge.

if you still have problems, let me know - I will need to review the .discharge file and schematic
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- cao001 @ Jon_oc on Jun 11, 2012 11:04 PM
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  Thanks for you feedback and comments, the links explained easily the .discharge.
  I understood better the .dscharge routine.....now I would like to know how the node will be printed in the ticket when it fails? have I generated a routine in the testplan?
  at the moment if the node is not discharge the ticket say only : "board not tested"
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  - Jon_oc @ cao001 on Jun 14, 2012 2:12 AM
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    Hi, if you have a problem with discharge the board - this is not a general failure that is reported to the operator, this needs to be resolved within debug.
    
    so you have a large capacitor that is not being discharged, this is a problem with the design that you have to overcome - and then there is no need to have this information returned to the operator.
    
    you can review the .discharge file and see which net has most capacitors - this will large capacitor on power rails (so VCC, +5V, +12V etc..) or look in BOM to see what are largest capacitors (very high uF or mF)
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Lee.D May 23, 2012 6:45 AM
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Other common issues are:

If you have a battery installed on the board at ICT it will never be able to discharge it and it will cause a failure. You will have to remove the + battery node from the discharge routine, and the pins and shorts tests.

If you have multiple isolated grounds, and they are not defined correctly in the board file, then sometimes it will not discharge the caps correctly.
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