What is Parasitic Power?
Parasitic Power is a term developed by Dallas Semiconductor to describe their method of powering their “1-Wire” devices. The DS18S20 sensor used by the TEMP08 is one of these 1-Wire devices. As the term implies, there is only one wire (well, 2 really. A ground is also required) used to communicate on a bus with all devices. The power is derived from the communication line. Whenever a logic “1” is sent on the 1-Wire bus, all devices on the bus use that logic “1” to charge up their internal circuitry. Providing that a logic “1” is sent often enough, that charge is sufficient to drive the individual devices. Fortunately, the idle state of the bus is a logic 1, so, statistically, a logic 1 is present very often.
