5V parasite power supply and 3V3 MCU

[HTD]

I have a requirement to use DS1820 temperature sensor in parasite mode, that needs 5V power supply (2 wires only) and STM32 MCU.

It works with 3V3 power supply, but there is increased measurement time, and it stops working over like 80°C.

I guess during the measurement I'd somehow have to provide 5V power supply to the sensor, but at the same time I can't connect it to the MCU.

Is there a way to trigger 5V pull-up from my MCU using transistors somehow?

[Andrew Neil]

It's a Maxim product - don't Maxim have guidance on this? It must, surely, be a common requirement...

[HTD]

It's actually Dallas. And it's probably not supported. It's designed to work with TTL, not CMOS. I've read documentation both from DS1820 and DS18B20. I have no problem with make DS18B20 or even DS18S20 work with my MCU, the problem is only with the obsolete DS1820 my client insist to use.

[Andrew Neil]

Maxim Tech Support: https://maximsupport.microsoftcrmportals.com/en-US/tech-support/

Perhaps take a look at App Note/TUTORIAL 148: GUIDELINES FOR RELIABLE LONG LINE 1- WIRE NETWORKS - which has this:

https://pdfserv.maximintegrated.com/en/an/AN148.pdf

you could base something on that ... ?

EDIT

https://maximsupport.microsoftcrmportals.com/en-US/search/?logicalNames=&q=1-wire+3v+3v3+microcontroller

[Andrew Neil]

@Adam �?yskawa​  "It's actually Dallas"

It hasn't been Dallas for decades!

Dallas were acquired by Maxim in 2001; the Dallas brand name continued in use until 2007

It is still an active product line:

https://www.maximintegrated.com/en/products/sensors/temperature-sensor-ics.html/tab1?fam=temp_sens&node=40881&metaTitle=Remote%20Temperature%20Sensors&374=OR%7C1-Wire%7C1-wire

The operation of the 1-Wire bus hasn't changed - what works for the DS18B20 and DS18S20 will work for the DS1820.

[waclawek.jan]

If it's still produced, it's now an Analog Devices product... ;)

If you want to switch on the +5V for pullup, you can either switch an PNP/PMOS using a 5-V tolerant pin set to open drain, to drive the base/gate through an adequate series resistor, pulled up to 5V using another suitable resistor. This is quite basic electronics, so I'm not sure why are you asking.

For the 1-wire bus itself, you again have to use a 5V-tolerant pin in STM32 of course, in open-drain configuration. If the 1-wire line goes outside of a box, consider using additional overvoltage protection devices.

JW

[Andrew Neil]

@Community member​ "If it's still produced, it's now an Analog Devices product"

They're still using the "Maxim" brand & website - for now:

 

Who knows how long that'll last ...

[waclawek.jan]

:D