wrote:
I recently got a free dell d600 laptop. The laptop is fine but it has
the notorious "The AC power adapter type cannot be determined"
problem.

I borrow a new ac adapter and the problem is solved.

I found out from a website that the dell ac adapter has some design
flaws.

http://www.laptop-junction.com/toast...r-id-chip-died

I don't want to keep buying AC adpter because of a bad id chips.
Is there any way to modify it other than using shield cable or moving
the power supply id chip to laptop?

So what is the design flaw ?

The one wire network is intended to support networks with a lot
of wire in them. With slew rate control, it is possible to make
decent looking waveforms, without upsetting the FCC. The devices
also have a high ESD rating. The communication rate is 16Kbit/sec
or so, sort of like the rates you might see on an RS-232 cable.
In the laptop adapter case, the network is relatively small,
compared to the device capabilities.

http://pdfserv.maxim-ic.com/en/an/AN148.pdf

The reliability report for the DS2501, shows some failures in high
voltage testing. The "HBM" entries would stand for "human body
model", which is a particular combination of RC network, charged
to the indicated voltage. So it is meeting "8KV HBM". (An Intel
USB port is 6KV rated, for comparison.) I don't know what the
"IEC 61000-4-2 CONTACT" test above it is all about, so cannot
comment on whether failures of that test can be ignored
as the report seems to be doing. It is almost as if they expect
the device to fail that particular test.

http://www.maxim-ic.com/reliability/dallas/DS2501.pdf

I couldn't get a datasheet for the DS2501 from Maxim, so had
to get one from datasheetarchive. It is a DS2502, but bulk
programmed. The bus voltage, according to this datasheet, is
2.8V to as high as 6.0V. So if the laptop-junction guy is
seeing 16 volts delivered, that is the amount of voltage
used for programming. What the effect would be on the
device, I haven't a clue (because programming is
probably another hard to find datasheet). If I was the laptop-junction
guy, I'd be comparing voltage level on the 1-wire, to
the range allowed by the datasheet. I'd feel happier if
I could get this sheet from Maxim.

http://www.datasheetarchive.com/sear...501&sType=part

The 1-wire family may exist with different bus voltages. Or
it could be, that the higher bus voltage is intended for
larger networks or something. In any case, I'd want to be
absolutely sure first, whether the application (Dell laptop),
is treating that poor chip properly. If the laptop has a problem,
and is abusing the ID chip, then it might kill them one
after another.

As for "moving it inside", that sounds like a good idea. Would
the chip be drawing power from the battery at all times ?
You'd almost need a schematic for the laptop, to get some
idea of how they're probing the thing, and what power source
is supposed to be used. Or what power source could be used
in a retrofit.

Any amount of external protection could be added to the 1-wire.
Like external ESD snubbing networks, a zener to limit bus
voltage, or whatever. It might not be just an unarmored
bus. Lots of fiddly little details...

As for the comment about "2 meter long UNSHIELDED wire",
unshielded wire is fine, with attention to details. The
bus is unterminated, but has slew rate limiting. So you
would not expect active signal radiation. It would be
possible for conducted emissions to travel down the wire,
but you could remove those with a ferrite bead, or a
filter cap etc. The filter cap could even be part
of the slew rate control network. For the 1-wire to work,
it needs a ground reference, and the ground wire traveling
in the cable next to the "antenna", reduces the loop size.
We don't know if the wires are twisted inside the cable
or not. Again, lots of little details.

So right now, I have only one question.

"What is 16.5V doing traveling to a 2.8 to 6V chip?"

HTH,
Paul