TC622 datasheet(5/14 Pages) MICROCHIP

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DS21440B-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, TSET,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 TSET

input and VCC. 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

RTRIP = 0.5997 x T

2.1312

Where:

RTRIP = Programming resistor value in Ohms

T = Desired trip temperature in degrees Kelvin.

RTRIP = 0.5997 x ((50 + 273.15)

2.1312) = 133.65kΩ

TEMPERATURE (˚C)

-55

-35

-15

105

125

100

150

200

250

Set Point

Temperature

OUT

(Set Point – 2 Degrees C)

OUT

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