Datasheet

TC646
DS21446D-page 10  2002-2012 Microchip Technology Inc.
5.0 TYPICAL APPLICATIONS
Designing with the TC646 involves the following:
(1) The temperature sensor network must be
configured to deliver 1.25V to 2.65V on V
IN
for 0%
to 100% of the temperature range to be regulated.
(2) The auto-shutdown temperature must be set
with a voltage divider on V
AS
.
(3) The output drive transistor and associated circuitry
must be selected.
(4) The SENSE network, R
SENSE
and C
SENSE
, 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 TC646 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 TC646 should consult the documenta-
tion for both TC642EV (DS21403) and TC642DEMO
(DS21401). Figure 5-1 shows the base schematic for
the TC642DEMO.
FIGURE 5-1: Typical Application Circuit.
FAULT
SENSE
NTC
R
1
R
2
R
3
R
4
GND
*See cautions regarding latch-up considerations in Section 5.0, "Typical Applications".
**Optional. See Section 5.0, "Typical Applications", for details.
NOTES:
Thermal
Shutdown
Shutdown**
Q
1
+12V
+5V*
V
DD
V
IN
V
AS
V
OUT
R
BASE
R
SENSE
C
SENSE
C
F
1μF
C
F
TC646
Fan
C
B
0.01μF
C
B
0.01μF
C
B
1μF
4
5
7
6
8
1
3
2
+5V