The TC620/TC621are solid-state temperature sensors
that are easy to program and interface with control
equipment. The TC620 senses the temperature inter-
nally, while the TC621 uses an external thermistor.
Figure 1 shows how the devices are connected.
The TC620/TC621 data sheet (DS21439) describes
how to calculate the correct resistance value for any
desired temperature. It also gives a graphical depiction
of the outputs for varying temperatures.
Since the TC620 senses temperatures internally, its
outputs must be limited to 1 mA. The device can source
or sink higher currents, but internal self-heating may
cause errors in the temperature sensing. The TC621
can source or sink 10 mA, since it uses an externalM AN773
Application Circuits of the TC620/TC621Solid-State
Temperature Sensors
thermistor to sense a remote temperature. Internal
Author: Microchip Technology Inc.
heating will not affect the temperature sensing
accuracy.
INTRODUCTION
Figure 2 is a schematic of a heating and cooling con-
The TC620/TC621are solid-state temperature sensors troller using a single TC620 and a TC4469 Quad
t……
