10R resistors are cheap so just add one to the circuit ;-)

Seriously, I would diagnose this by elimination. Since you can easily
observe the current spikes (and don't have to wait for the part to fail)
it should not be 2 difficult. Try for example to disconnect I/P and O/P
pins and C if the problem goes, or change the S/W to leave all the pins
as I/P (high Z) and enter an infinite loop and C what happens.

Tal

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Ian Forse
> Sent: Wednesday, May 14, 2003 2:26 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: Voltage regulator Problem with 12F675
>
>
> I am having a problem with a regulator and 12F675 both failing.
>
> The regulator is a ZMR50H (Zetex) regulator SOT23 with 5V @
> max 50mA O/P for up to 25V I/P, this device has a low
> quiescent current.
>
> The PIC is a 12F675 with an LM431 voltage reference (2.495V)
> for Vref, LED's on 3 O/P's, MCLR is a digital input and the
> other pin is a analogue input. The current consumption is
> around 17mA when operating.
>
> With 25V I/P to the regulator and a resistive load I have no
> problems.  When the PIC circuit is connected it blows (and
> the regulator) after being switched on a few times.  It is
> not possible to tell which goes first but I believe it is the
> regulator follwed by the PIC.
>
> I have measured the current into the PIC on the +ve and 0V
> lines with a 10R resistor and I find large current spikes,
> seen on a scope, of up to 800mA at power up.  If the 10R
> resistor is in circuit the PIC and regulator survive.
>
> I have tried modifying the CONFIG with WDTE and BODEN but
> this makes no differance.  Has anyone else seen this problem
> and if so can it be fixed in software or is it a Microchip
> silicon problem?
>
> Regards
>
> Ian
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