Searching \ for 'Burning pins on a PIC (was Re: pic max voltage)' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/power.htm?key=voltage
Search entire site for: 'Burning pins on a PIC (was Re: pic max voltage)'.

Truncated match.
PICList Thread
'Burning pins on a PIC (was Re: pic max voltage)'
1998\04\01@081412 by Marc Heuler

flavicon
face
Hi Bob (Bob Blick), in <spam_OUTPine.LNX.3.95.980330121436.6753A-100000TakeThisOuTspamblick1.mhs.mendocino.k12.ca.us> on Mar 30 you wrote:

> Have lost pins at 9 volts, and the chip stops, but works again at normal
> voltages(without the pins that burned out).

That's interesting.

Some time ago I was interested in protecting PICs more than just setting
the fuse bit.  Burning an IO pin that plays an important role during
program/read/verify comes to mind as a good start.  Popping the PIC would
then involve opening the package (which is possible but quite a mess, and
not known to many hobby attackers).

However, I did not find a reliable way to just burn the one IO pin, leaving
the rest of the PIC functional.  I did have _some_ success by shorting all
pins to ground, and applying lots of volts/amps to the prg IO pin.  At
about 1.5A the current draw suddenly stopped, indicating the pin is burned.

Did anyone of you work out a procedure to burn pins without the risk of
damaging the PIC?

1998\04\01@114912 by Bob Blick

face
flavicon
face
>
> > Have lost pins at 9 volts, and the chip stops, but works again at normal
> > voltages(without the pins that burned out).
>
> That's interesting.
>
> Some time ago I was interested in protecting PICs more than just setting
> the fuse bit.  Burning an IO pin that plays an important role during

Actually, I should have said that after running the PIC at 9 volts, any
pins lost still seemed to work fine as inputs :-)

Cheers,
Bob

1998\04\01@123718 by Morgan Olsson

picon face
At 08:23 1998-04-01 -0800, you wrote:
>>
>> > Have lost pins at 9 volts, and the chip stops, but works again at normal
>> > voltages(without the pins that burned out).
>>
>> That's interesting.
>>
>> Some time ago I was interested in protecting PICs more than just setting
>> the fuse bit.  Burning an IO pin that plays an important role during
>
>Actually, I should have said that after running the PIC at 9 volts, any
>pins lost still seemed to work fine as inputs :-)

Even better, if we then just can make reading out program impossible, but
still can use the pin as input.

But I am really worried about
1)      Lifetime (we must have hurt something?)
2)      Some exessive cirrent drawn by the destroyed output.
3)      Lowered input impedance etc due to partly destruction?

Did you test input parameters change or supply current change?

/Morgan

>Cheers,
>Bob
>
>
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  .....mrtKILLspamspam@spam@iname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\04\01@160212 by Alessandro Zummo

flavicon
face
Il 01-Apr-98, Bob Blick scrisse:

>>> Have lost pins at 9 volts, and the chip stops, but works again at normal
>>> voltages(without the pins that burned out).
>>
>> That's interesting.
>>
>> Some time ago I was interested in protecting PICs more than just setting
>> the fuse bit.  Burning an IO pin that plays an important role during

> Actually, I should have said that after running the PIC at 9 volts, any
> pins lost still seemed to work fine as inputs :-)

That's fine.. if someone will decide to try such a kind
of protection, please report the result to the list!

--

  - *Alex* -

 http://freepage.logicom.it/azummo/

1998\04\02@030819 by Brett Paulin

flavicon
face
G'day PicListers

>>>> Have lost pins at 9 volts, and the chip stops, but works again at normal
>>>> voltages(without the pins that burned out).
>>> Some time ago I was interested in protecting PICs more than just setting
>>> the fuse bit.  Burning an IO pin that plays an important role during
>That's fine.. if someone will decide to try such a kind
>of protection, please report the result to the list!

I used to work at a place in the Electronic Security Industry that manufactured
a Single-Chip Micro (68705) powered Alarm panel.   In the security industry..
"Pirating" of monitoring clients is a big game..   Company "A" does the
installation of the security system at a bargain basement price, assuming that
they will make their money over the next 12 months from the monitoring fees
that the client pays to the watching station (Dialling security systems).

Company "B" comes in, offers the client a cheaper price on monitoring, and
changes the telephone number and client code programmed into the unit, and
picks up a client without the associated installation cost.    Most security
systems have a set of pins on the PCB that you short together to erase the
access codes to the system in the event of forgetting the master access code or
something..

It came to our attention that some clever installer had found that applying a 9v
battery backwards (the pin spacing was ideal) to these pins would effectively
blow up (burn) that input to the micro, without affecting the rest of the
operation, and prevent the erasure of the EE stored access codes, thus
preventing pirating, unless the pirating company was willing to replace the
Micro and EEprom of the security system.. whcih if course required complete
reprogramming of the system parameters, and make takeover a lot harder..

We saw quite a few of these "Fried" Micros over the period of a few years, and
they never seemed to be bothered in the reliability dept.  I wonder if the PIC
series is the same..


---
Brett Paulin : Trance DJ Spock, Electronic Engineer & Gyrocopter Pilot
For DAT trading, DJ Spock & Techno Magic - http://home.mira.net/~rando
      THINK for yourself, QUESTION Authority   - ICQ Id# 5879520

1998\04\02@160432 by Jens.Madsen

flavicon
face
It is normal that CMOS chips survive a much higher voltage if there is
no change on signals. E.g. HCMOS typical only use few uA at 18V, even
they only is made for 6V, as max.

It may be a way to burn inputs too by applying high voltage, and then
switch the input to burn by a high frequence. This will only dammage the
logic that is toggleing. Reset is constant active, and oscilator need to
be stopped. I think that the PIC only use few uA under these conditions,
and that it is possible to burn an input.

It is problems with reciveing PICLIST from denmark, and I have not
recived any emails. Try again if it was problems.

Regards,
Jens Dyekjfr Madsen

1998\04\02@174937 by Jens Dyekjaer Madsen

picon face
It is normal that CMOS chips survive a much higher voltage if there is
no change on signals. E.g. HCMOS typical only use few uA at 18V, even
they only is made for 6V, as max.

It may be a way to burn inputs too by applying high voltage, and then
switch the input to burn by a high frequence. This will only dammage the
logic that is toggleing. Reset is constant active, and oscilator need to
be stopped. I think that the PIC only use few uA under these conditions,
and that it is possible to burn an input.

Regards,
Jens Dyekjfr Madsen


______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com

1998\04\03@075847 by Jens.Madsen

flavicon
face
Morgan Olsson wrote:
{Quote hidden}

I have not testet it with PIC's, but with HC4049. It was possible to use
18V with only few uA as supply when all signals not toggleing. It was
easy to burn an input. In this case, it only affected the inverter that
I was toggling. It was a higher frequence, maybee 40-80MHz, but lower
may be good too.

I suggest to make an autoregulating power supply, that increase the
voltage when MCLR and oscilator stopped, and adjust the voltage to as
high voltage as possible, but without using more than e.g. few uA.

When voltage rised, then apply the frequence for the input to burn.

As example of circuit

         *--------*--------*----- 30V
         |        |        |
        |-|       |        |
        | | R1    |    Q2  |
        |-|       |     /--|--\
         |        |     |  |  |
         *--------|-----|--|--|
     V1  |        |     | \|/ |
         |    Q1  |     \--|--/
         |     /--|--\     |
         |     |  |  |     |
         |     |--|--|-----*
         |     | \|/ |     |
         |     \--|--/     |
         |        |        |
         *--------*        |
     Vcc |                 |    C1
   -------------        -------
   |   P I C   |        -------
   |           |           |
   -------------           |
     Vss |                 |
         *-----------------*----- 0V

R1 limits the current to the PIC to few uA at power on. The voltage V1
rise to as high voltage with low current as possible. C1 is charged to
this voltage, and hold it when a large current is pulled when toggling
inputs.

I have not testet it with a PIC, and the current may be high because of
analog logic, or oscilator logic. It deppend on mode of the oscilator
too.

Maybee it takes more logic than needed, and makes it more difficult to
get the values from chip.

Regards,
Jens Dyekjaer Madsen

More... (looser matching)
- Last day of these posts
- In 1998 , 1999 only
- Today
- New search...