1-wire specification

Discussion in 'Electronic Design' started by Raveninghorde, Jan 11, 2010.

  1. 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.
     
    Raveninghorde, Jan 11, 2010
    #1
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  2. On Mon, 11 Jan 2010 11:49:46 -0700, Jim Thompson
    </Snicker> wrote:

    >On Mon, 11 Jan 2010 18:40:35 +0000, Raveninghorde
    ><raveninghorde@invalid> wrote:
    >
    >>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.

    >
    >330 Ohms would imply something like 2.2K _minimum_ pull-up.
    >
    > ...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.
     
    Raveninghorde, Jan 11, 2010
    #2
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  3. Raveninghorde

    Mark Zenier Guest

    In article <>,
    WangoTango <> wrote:
    ....
    >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.


    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
    Googleproofaddress(account:mzenier provider:eskimo domain:com)
     
    Mark Zenier, Jan 12, 2010
    #3
  4. Raveninghorde

    Mark Zenier Guest

    In article <>,
    WangoTango <> wrote:
    >In article <>, says...
    >> In article <>,
    >> WangoTango <> wrote:
    >> ...
    >> >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.

    >>
    >> 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
    >> Googleproofaddress(account:mzenier provider:eskimo domain:com)

    >
    >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? :)


    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
    Googleproofaddress(account:mzenier provider:eskimo domain:com)
     
    Mark Zenier, Jan 14, 2010
    #4
  5. Raveninghorde

    Jon Kirwan Guest

    On Thu, 14 Jan 2010 20:08:29 GMT, (Mark
    Zenier) wrote:

    >In article <>,
    >WangoTango <> wrote:
    >>In article <>, says...
    >>> In article <>,
    >>> WangoTango <> wrote:
    >>> ...
    >>> >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.
    >>>
    >>> 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
    >>> Googleproofaddress(account:mzenier provider:eskimo domain:com)

    >>
    >>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? :)

    >
    >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
    >Googleproofaddress(account:mzenier provider:eskimo domain:com)


    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
     
    Jon Kirwan, Jan 15, 2010
    #5
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