To all, Concerning the DS2436 operation:.
To the best of my knowledge the DS2436 apparently uses a dual diode internally, one side from the DQ line and the other from the VDD line. However when doing voltage conversion it has to run an internal A/D unit. Since if the VDD is unpowered or low voltage only the DQ line is acting as the supply this would be the reason why accuracy would degrade as it drops below the minimal 1-wire voltage. The same holds true for the Temp conversions. I am unsure if with some care on the 1-wire signals, if you couldn't supply enough current for a successful conversion. But you probably couldn't be doing any activity on the bus till it was done (and therefore couldn't check the status bit) since it would drop the supply voltage. So you would have to hold it high till enough time for a conversion was complete. (10ms). Anyway, that's my guess at it (haven't tried it). Checking the status bit would lower the voltage available depending on the activity happing on the bus. The VDD would never be tied to ground as by nature the chip really is in parasitic operation all the time. (it tapping the DQ and whatever voltage is available at the A/D input or VDD line). Its very similar to the DS2438 if you consider this pin to be the same as the DS2438's VDD line which it also monitors. Concerning the use of DS2450 for new work: I'd not recommend the DS2450 chip for anything these days.. its definitely the worst of the 1-wire chips out there (and need to be replaced by Dallas). Most of the hardware manufacturing people have gone through real problems with this chip. .Instead I'd look to use multiple DS2438's. The DS2450 costs $5.98 and the DS2438 $1.97 in single quantities so this is reasonable, and besides you end up with a lot more capability with the 4 DS2438's and much better operation and performance). BTW.. Dallas just announced a new chip a few days ago...the DS2781E+ It similar to DS2438, (different pads though) Temp not as good, (smt devices have their own set of problems anyway, so I like to use a seperate sensor for this normally), and has a 16bit current sense and a PIO..could be interesting. Dave David Lissiuk Sr. Computer Scientist Springbok Digitronics ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=103432&bid=230486&dat=121642 _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
