MGSF1N02E View Datasheet(PDF) - Microchip Technology
Part Name
Description
Manufacturer
MGSF1N02E Datasheet PDF : 28 Pages
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TC642
5.0 TYPICAL APPLICATIONS
Designing with the TC642 involves the following:
(1) The temp sensor network must be configured to
deliver 1.25V to 2.65V on VIN for 0% to 100% of the
temperature range to be regulated.
(2) The minimum fan speed (VMIN) must be set.
(3) The output drive transistor and associated circuitry
must be selected.
(4) The SENSE network, RSENSE and CSENSE, must
be designed for maximum efficiency, while
delivering adequate signal amplitude.
(5) If shutdown capability is desired, the drive require-
ments of the external signal or circuit must be
considered.
The TC642 demonstration and prototyping board
(TC642DEMO), and the TC642 Evaluation Kit
(TC642EV), provide working examples of TC642 cir-
cuits and prototyping aids. The TC642DEMO is a
printed circuit board optimized for small size and ease
of inclusion into system prototypes. The TC642EV is a
larger board intended for benchtop development and
analysis. At the very least, anyone contemplating a
design using the TC642 should consult the documen-
tation for both TC642EV (DS21403) and TC642DEMO
(DS21401).
+5V*
Shutdown
(Optional)
R1
NTC
CB
1 µF
8
1
VIN
VDD
CB
R2
0.01 µF
FAULT 6
R3
3 VMIN
CB
0.01 µF
2
R4
CF
CF
1 µF
TC642 VOUT 7
SENSE 5
GND
4
+12V
Fan
Thermal
Shutdown
Q1
RBASE
CSENSE
RSENSE
Note: *See cautions regarding latch-up considerations in Section 5.0, "Typical Applications".
FIGURE 5-1:
Typical Application Circuit.
5.1 Temperature Sensor Design
The temperature signal connected to VIN must output a
voltage in the range of 1.25V to 2.65V (typical) for 0%
to 100% of the temperature range of interest. The
circuit in Figure 5-2 illustrates a convenient way to
provide this signal.
Figure 5-2 shows a simple temperature dependent
voltage divider circuit. RT1 is a conventional NTC ther-
mistor while R1 and R2 are standard resistors. The sup-
ply voltage, VDD, is divided between R2 and the parallel
combination of RT1 and R1 (for convenience, the paral-
lel combination of RT1 and R1 will be referred to as
RTEMP). The resistance of the thermistor at various
temperatures is obtained from the manufacturer’s
specifications. Thermistors are often referred to in
terms of their resistance at 25°C.
2002 Microchip Technology Inc.
DS21444C-page 9
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