1-wire specification

I am using a DS2438 as a battery monitor. The app notes recommend a series 330 ohm in the DQ line for static protection. The data sheet shows 4k7 as the master pull up resistor.

I have a Link45 serial to 1-wire interface and the cooms does not work. A quick check shows a 1k bus pull up. So the 330 ohm is not allowing the output from the battery to get lower than about 1.2V.

Is there actually a specified min and max for the bus pull up resistor. I.m looking but haven't found a specification yet.

Reply to
Raveninghorde
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330 Ohms would imply something like 2.2K _minimum_ pull-up. ...Jim Thompson
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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Your math isn't too bad ;-)

I am seeing Maxim app notes for 1-wire on long cables saying 1k may be needed. This of course doesn't work with the Maxim app notes saying fit a 330 ohm resistor for static protection. So it looks like I have to design for 1k pull up. Just wish I could find a spec giving min and max figures.

Who writes app notes? Certainly no one who knows what they are doing.

Reply to
Raveninghorde

At Motorola it was a department separate from the design groups :-(

I was constantly at clash with those idiots. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

I still remember the convoluted spec on the NMOS MC68705P3S port A. I went something like this :

"The PORT A pull up option, available on the masked part, is not optional on the ceramic (CS) part"

OK, does that mean it is always in place, or not available? When I called the regional FAE he didn't know either.

Reply to
WangoTango

I interpret that as a direct implication of NO pullup.

Reply to
Robert Baer

I did too, but it could have been a lot more clearly stated. It was simple enough to test for, but I expect a bit more clarity when it comes to spec sheets. A non-optional option could be construed to mean it is a mandatory addition. Something along the lines of "The PORT A pull up is not available on the ceramic (CS) part." TADA.....

Reply to
WangoTango

In article , WangoTango wrote: ...

Should be buried in the spec sheet somewhere. Dig, dig, dig ... ADI-1031, October, 1984.

Compare the 6805P2 and 68705P3 "Port DC Characteristics" pages in the back. There's only one section for the 705P3 Port A characteristics. But for the P2, there are two. So find the one that's the best match. "Iih" for Port A in the 705P3 matched the characteristics of "Iih" for port A on the the P2 "with CMOS Drive Enabled". So, always enabled.

Took me about 5 minutes to answer a question that's 25 years obselete. ;-)

Mark Zenier snipped-for-privacy@eskimo.com Googleproofaddress(account:mzenier provider:eskimo domain:com)

Reply to
Mark Zenier

..but....but........that is toooo symple!

Reply to
Robert Baer

The point was that there should be a bit more clarity to begin with, not that the question couldn't be answered with some digging.

And, shouldn't there be TWO listing for PORTA also? One for the masked part when the customer opts for the optional option and one for when they don't? :)

Reply to
WangoTango

I thought that's what I said. " But for the P2, there are two. " Meaning, they have two sections in the MC6805P2 (and 'P4 and 'P6) "Port DC Electrical Characteristics" table of the spec sheet, one for "Port A with CMOS Drive enabled", and one for "Port C and Port A with CMOS Drive Disabled". Giving VOL, VOH, VIL, and VIH under various conditions. The "drive enabled" section matches the '705P3' table in having both the additional "VOH with a 10 uA load" spec, and having the higher IIH spec.

Mark Zenier snipped-for-privacy@eskimo.com Googleproofaddress(account:mzenier provider:eskimo domain:com)

Reply to
Mark Zenier

Mark, I think your answer was tight and targeted at the OP's first post well. I think Asgard24's response tried to change the subject, writing "The point was that there should be a bit more clarity to begin with, not that the question couldn't be answered with some digging." That hadn't been the OP's point, but it was a point Asgard24 tried to turn it into for reasons I don't fathom well.

You were right to write as you did. It was on point and nicely said.

Jon

Reply to
Jon Kirwan

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