Lpc2000

Hi All

we are using the LPC2106 to read some serial data (among other 
things) from an external device (about 5" away via flat band cable 
in the same equipment driven by 3V3).

During the development we noticed that a couple of prototypes 
stopped working properly and the ports seemed to have been destroyed 
(we couldn't toggle them any more). "May be we applied a high 
voltage or something we decided and, after changing the chip, forgot 
it.

Now we have manufactured about 1000 pieces of equipment and have 
been suprised with the high failure rate in the test. From the 
errors associated with reading the data from the external chip we 
have a high percentage due to failure of ports in the LPC2106 (2..3% 
of batch) - either they don't work or we can measure a low impedance 
short circuit to ground.

We can assume it is not due to handling because their production is 
at a quality production company.

There are a few hundred in the field and we don't know of failures 
after leaving the test field...

There are some other errors which we haven't studied in detail which 
may be concerned with other ports (used for local bit banging), I'll 
know next week once the failure causes are known.

Has any one experience or details about this type of failure or 
possible causes? There are no high voltage involved, the chip it 
reads data from is 3V3 and required only a few uA so what can be 
doing the damage???

Regards

Mark Butcher

www.mjbc.ch

----- Original Message ----- 

From: "Mark Butcher" <M_J_Butcher@...>
To: <lpc2000@yahoogroups.com>
Sent: Friday, August 26, 2005 11:17 PM
Subject: [lpc2000] LPC2106 Ports (sensitivity to destruction?)


> Hi All
>
> we are using the LPC2106 to read some serial data (among other
> things) from an external device (about 5" away via flat band cable
> in the same equipment driven by 3V3).
>
> During the development we noticed that a couple of prototypes
> stopped working properly and the ports seemed to have been destroyed
> (we couldn't toggle them any more). "May be we applied a high
> voltage or something we decided and, after changing the chip, forgot
> it.
>
> Now we have manufactured about 1000 pieces of equipment and have
> been suprised with the high failure rate in the test. From the
> errors associated with reading the data from the external chip we
> have a high percentage due to failure of ports in the LPC2106 (2..3%
> of batch) - either they don't work or we can measure a low impedance
> short circuit to ground.
>
> We can assume it is not due to handling because their production is
> at a quality production company.
>
> There are a few hundred in the field and we don't know of failures
> after leaving the test field...
>
> There are some other errors which we haven't studied in detail which
> may be concerned with other ports (used for local bit banging), I'll
> know next week once the failure causes are known.
>
> Has any one experience or details about this type of failure or
> possible causes? There are no high voltage involved, the chip it
> reads data from is 3V3 and required only a few uA so what can be
> doing the damage???

Something might be happening when you are connecting the units together. I'd 
be inclined to put something like 3.3 V Transguards (made by AVX) on all the 
lines.

Leon 



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Hi Leon
The two units are internal to the equipment (simply 2 internal board 
connected by flat band) and the two board are never 
disconnected/connected.
There are diodes clamping over and under voltage to the 3V3 / 0V rails 
(like in most chips to protect inputs).

By the way there was a unit which I measured which was getting quite 
hot (not a port issue) and I found that there was a power supply 
problem and the LPC2106 was getting 7V8 instead of 3V3. It was getting 
very hot but otherwise the equipment was still worked fine.....(not to 
be advised though ;-)  )

Regards

Mark
www.mjbc.ch

> 
> Something might be happening when you are connecting the units 
together. I'd 
> be inclined to put something like 3.3 V Transguards (made by AVX) on 
all the 

> lines.
> 
> Leon