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Maxim > Design Support > Technical Documents > Application Notes > Temperature Sensors and Thermal Management > APP 1075
Keywords: temperature sensor, switch, isolated temperature sensor, isolated temperature detector,
temperature sensing, temp sensors, single wire sensors
APPLICATION NOTE 1075
Simplify Isolated Temperature Sensing With Single
Wire Sensors
May 24, 2002
Abstract: Many temperature sensing applications require galvanic isolation of the sensor. Fortunately, several
low-cost temperature-sensing integrated circuits (ICs) are easy to isolate. This application note shows two
approaches to isolating temperature sensors.
A similar version of this article appeared in the June 6, 2000 issue of Electronic Design magazine.
Sensors, such as temperature sensors, require galvanic isolation when they are mounted in "mechanically
inconvenient" locations such as electrically noisy environments, poorly grounded environments, of instances
where lack of isolation causes safety issues. New families of temperature sensors ease the design of isolated
systems by virtue of a new simple, single-wire method with digitally-multiplexed outputs. These new devices
also offer very low power consumption, simplifying the choices and cost of providing power to the isolated
side.
Isolating a temperature sensor with a unidirectional output is straightforward. An example is a temperature
sensor with a frequency or period output, or a thermostatic switch output as shown in Figure 1. This circuit
can take advantage of a new family of sensors such as the MAX6576, whose period is proportional to
temperature, or the MAX6577 whose frequency varies with temperature. Maxim also provides the MAX6501
through MAX6506, a family of temperature switches (simple devices with outputs that become active at a pre-
defined temperature) which could also be used in this circuit.
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