Dan Azari

Internal Voltage Regualtor mishap - MC9S12DG128 added p/n to subject.

Discussion created by Dan Azari on Oct 19, 2008
Latest reply on Oct 27, 2008 by DPB
I am hoping that someone can explain the damaged caused by applying 5VDC to VDD1,VDD2, and VDDPLL while the Internal Voltage Regulator is enabled.  On a small run of a project using an MC9S12DG128 with Pierce osc configuration we incorrectly supplied 5VDC to the internal voltage regulator filter pins.  These boards all worked properly upon intial programming.  However, we have had a high failure rate in the field with processors failing to start or unreliably starting after several weeks of use.  I suspect the problem is damage to the silicon and VCO circuitry and would appreciate some expert opinions.
On one such processor that failed in the field I have noticed the following--
With 5VDC still applied to VDD1, VDD2 and VDDPLL the unit boots in the lab, and I am able to use a BDM debugger.
When I disconnected 5VDC from these pins and placed 100nf caps, all three outputs measure 2.5VDC.  However, the oscillator does not appear to start correctly and I can not connect with a BDM pod.  The mcu will only start if 5VDC is aplied to all three of these pins.
On a new design with this problem corrected, mcu boot normall using identical components on the oscillator and vco, so I suspect that the unit above does have some damage to the silicon.
Thanks in advance,
Added p/n to subject.

Message Edited by NLFSJ on 2008-10-20 10:29 AM