Datasheet

 2001-2012 Microchip Technology Inc. DS21440D-page 5
TC622/TC624
3.0 DETAILED DESCRIPTION
3.1 Trip Point Programming
When the temperature of the device exceeds the pro-
grammed temperature trip point, T
SET
, the OUT and
OUT
outputs are driven into their active states. The
desired trip point temperature is programmed with a
single external resistor connected between the T
SET
input and V
CC
. The relationship between the resistor
value and the trip point temperature is given by
Equation 3-1.
EQUATION 3-1:
For example, as shown in Figure 3-1, to program the
device to trip at 50°C, the programming resistor is:
FIGURE 3-1: Programming Resistor
Values vs. Temperature
3.2 Hysteresis
To prevent output “chattering” at the trip point tempera-
ture, the temperature detector in the TC622/TC624 has
2°C hysteresis (see Figure 3-2). The outputs are driven
active when the temperature crosses the set point
determined by the external resistor. As temperature
declines below the set point, the hysteresis action will
hold the outputs true until the temperature drops 2°C
below the threshold.
FIGURE 3-2: TC622/TC624 Hysteresis
R
TRIP
= 0.5997 x T
2.1312
Where:
R
TRIP
= Programming resistor value in Ohms
T = Desired trip temperature in degrees Kelvin.
R
TRIP
= 0.5997 x ((50 + 273.15)
2.1312
) = 133.65 k
TEMPERATURE (°C)
RESISTANCE, R
TRIP
(kΩ)
-55 -35 -15 5 25 45 65 85 105 125
50
100
150
200
250
Set Point
Temperature
OUT
(Set Point – 2 Degrees C)
OUT