TC622/TC624
DS21440D-page 6 2001-2012 Microchip Technology Inc.
4.0 TYPICAL APPLICATIONS
4.1 Over-Temperature Shutdown
The TC622 can be used to create 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
temperature set by R
TRIP
. When this happens, the
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
temperature rises above T
SET
and remains on until the
temperature falls below T
SET
- 2°C.
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
T
C
622
TC622
R
TRIP
V
CC
Output Device
Heatsink Surface
Power Good
Signal
OVERTEMP
Crowbar
Circuit
T
SET
GND
V
DD
V
OUT
OUT
OUT
Output
Device
