1-wire specification
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From: Raveninghorde on 11 Jan 2010 13:40 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.
From: Jim Thompson on 11 Jan 2010 13:49 On Mon, 11 Jan 2010 18:40:35 +0000, Raveninghorde <raveninghorde(a)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 -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Raveninghorde on 11 Jan 2010 14:04 On Mon, 11 Jan 2010 11:49:46 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: >On Mon, 11 Jan 2010 18:40:35 +0000, Raveninghorde ><raveninghorde(a)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.
From: Jim Thompson on 11 Jan 2010 14:07 On Mon, 11 Jan 2010 19:04:02 +0000, Raveninghorde <raveninghorde(a)invalid> wrote: >On Mon, 11 Jan 2010 11:49:46 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: > >>On Mon, 11 Jan 2010 18:40:35 +0000, Raveninghorde >><raveninghorde(a)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. At Motorola it was a department separate from the design groups :-( I was constantly at clash with those idiots. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: WangoTango on 11 Jan 2010 14:42
In article <jmtmk59k4quv15uoqtm9lv4h7s4mj59r43(a)4ax.com>, To-Email-Use- The-Envelope-Icon(a)My-Web-Site.com/Snicker says... > >Who writes app notes? Certainly no one who knows what they are doing. > > At Motorola it was a department separate from the design groups :-( > > I was constantly at clash with those idiots. > > 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. |