Dallas DS1920 & DS1820

The DS1820 and DS1920 is a Dallas 1-wire device for temperature measurement. There were various versions of the DS1820 devices. One was marked DS1820PAR and only worked in parasitic mode. The DS18S20 uses a bandgap temperature sensing architecture rather than the dual-oscillator architecture used by the DS1820. This architectural difference is invisible to the user. The primary specification difference between the two parts is the temperature conversion time: DS1820 = 500ms (max) and DS18S20 = 750ms (max). The DS18S20 is software compatible with the DS1820 in most applications.

The DS18S20 is available in TO92 (DS18S20) and 8-pin SOIC (DS18S20Z) packages. The DS18S20 (TO92 package) replaces the DS1820 (PR35 package) since both packages are 3-pin packages with the same lead pitch. There is no replacement package for the DS1820S (16-pin SSOP); however, the DS18S20Z (8-pin SOIC) provides a smaller surface mount package option.

There is also a DS18B20 which is not code compatible with the DS18S20. The differences are explained here. Some versions are marked with a '+' and this signifies a lead-free RoHS-compliant package.

Further Reading

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