TC621 Microchip Technology Inc., TC621 Datasheet - Page 7

• Manufacturer Part Number: TC621
• Description: 5v, Dual Trip Point Temperature Sensors
• Manufacturer: Microchip Technology Inc.

4.0
4.1
In Figure 4-1, the Dual Speed Temperature Control
uses a TC620 and a TC4469 quad driver. Two of the
drivers of the TC4469 are configured in a simple oscil-
lator. When the temperature is below the LOW TEMP
set point, the output of the driver is OFF. When the tem-
perature exceeds the LOW TEMP set point, the
TC4469 gates the oscillator signal to the outputs of the
driver. This square wave signal modulates the remain-
ing outputs and drives the motor at a low speed. If this
speed cannot keep the temperature below the HIGH
TEMP set point, then the driver turns on continuously
which increases the fan speed to high. The TC620 will
monitor the temperature and only allow the fan to oper-
ate when needed and at the required speed to maintain
the desired temperature. A higher power option can be
designed by adding a resistor and a power MOSFET.
FIGURE 4-1:
FIGURE 4-2:
© 2006 Microchip Technology Inc.
Low Temp.
High Temp.
30 C
50 C
TYPICAL APPLICATIONS
Dual Speed Temperature Control
Temperature Scale
0 C
˚
˚
˚
R
R
High Temp.
Low Temp.
H
L
– 30 C (Fan Off)
– 50 C (Fan Low)
– UP (Fan High)
30 C ˚
50 C ˚
˚
˚
1
2
3
4
TC620
Dual Speed Temperature Control
Temperature Controlled Fan
2
3
1
5
TC620
Limit
Limit
High
Low
4
8
0.1 µF
8
7
6
5
6
7
1N4148
1N4148
+12V
1 µF
MTP3055E
Fan Motor
10 µF
10k
2
1
3
5
8
TC4469
+12V
14
7
Low Temp.
4.2
In the application in Figure 4-2, a high and a low tem-
perature is selected by two R
monitors the ambient temperature and turns the FET
switch on when the temperature exceeds the HIGH
TEMP set point. The fan remains on until the tempera-
ture decreases to the LOW TEMP set point. This
provides the hysteresis. In this application, the fan
turns on only when required.
The TC621 uses an external thermistor to monitor the
ambient temperature. This adds one part, but allows
more flexibility with the location of the temperature
sensor.
13
4
6
9
10
11
12
Temp.
High
50 pF
R
100k
R
1M
Temperature Controlled Fan
H
L
1
2
3
4
Thermistor
TC621
TC620/TC621
(NTC)
50 Ω
Higher Power Option
Fan Motor
8
7
6
5
L
V MOTOR
and R
MOSFET
+12V
Fan Motor
DS21439C-page 7
MTP3055E
H
Fan Motor
. The TC620