What is parasitic power mode (DS1820)

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Just fell over this

Dallas DS18B20-PAR, 3 term TO-92 package.

For use in applications where the DS1820 is operated in the parasitic power mode. Term 1 is GRD, term 2 is DQ. Term 3 is not used, but may be grounded

What is parasitic power mode :?: :?:

Doesn't the non par of the Dallas use just 2 wires ???

/Bingo

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Parasitic power mode means that it extracts all of its operating power from the serial interface line. No local power supply is needed in that case.

I think that this mode (in general for one-wire) adds some restraints to the protocol. Perhaps its data rate or something like that.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Thanx for the ansver :)

Hmmm

Does that mean that the PAR version of the chip is "Special" (i might think so) or could a normal DS1820 be run in parasitic mode ??

I just got a cpl of DS1821 ,from Maxim :D :D

But if i use a PDS then i guess i could just feed the 5v in another wire if it isnt parasitic , correct ???

How would one do that on a "Long Run" use 12v on the wire and a 7805 for each DS18xx or :?: :?:

How far can you go with those things (one wire things) , approx ??

/Bingo

/Bingo

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Just checked DS1820 on Maxim web site. It says "no longer available" and use DS18S20.

It says that the Vdd pin is grounded to put it into parasitic mode. When power is supplied locally, its good with 3.0V to 5.5V. I know of applications ("weather stations") where they are connected over 10's of feet, if not further. They may need a smaller pullup in that case.

I could not find any reference to "par version".

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Thank you

 

Last Edited: Sat. May 28, 2022 - 08:42 PM