TC622/TC624

DS21440B-page 6

© 2002 Microchip Technology Inc.

4.0

TYPICAL APPLICATIONS

4.1

Over-Temperature Shutdown

TheTC622 canbe used tocreate a simple over-tem-

perature shutdown circuit. In this circuit, temperature is

sensed within the system enclosure (internal system

ambient) or at the heatsink itself. When measured

temperature exceeds a preset limit, a fault is indicated

and the system shuts down.

Figure 4-1 illustrates an over-temperature shutdown

circuit using the TC622 sensor in a single TO-220

package, allowing direct attachment to the heatsink

surface. As shown, the TC622 outputs are driven active

when the heatsink temperature equals the trip point

crowbar circuit is activated, causing the supply output

to fold back to zero. The TC622 outputs remain active

until the heatsink temperature falls a minimum of 2°C

(built-in hysteresis) below the trip point temperature, at

which time the device again allows normal supply

operation.

4.2

Cooling and Heating Applications

The TC622/TC624 can be used to control a DC fan as

shown in Figure 4-2. The fan turns on when the sensed

Figure 4-3 shows the TC622 acting as a heater

thermostat. Circuit operation is identical to that of the

cooling fan application.

FIGURE 4-1:

TC622 POWER SUPPLY OVER-TEMPERATURE SHUTDOWN

Heatsink

Circuit Board

TC622 Heatsink Mounting

TC622

TC622

Output Device

Heatsink Surface

Power Good

Signal

OVERTEMP

Crowbar

Circuit

GND

OUT

OUT

Output

Device