TC642EV Microchip Technology, TC642EV Datasheet - Page 13

• Manufacturer Part Number: TC642EV
• Description: KIT EVALUATION FOR TC642
• Manufacturer: Microchip Technology

Specifications of TC642EV

• Processor To Be Evaluated: TC642 and TC646
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: Q698359

Some applications require the fan to be powered from
the negative 12V supply to keep motor noise out of the
positive voltage power supplies. As is shown in
Figure 5-8, zener diode D
ply voltage, holding transistor Q
FIGURE 5-7:
FIGURE 5-8:
V
2002 Microchip Technology Inc.
OUT
a) Single Bipolar Transistor
R
BASE
Output Drive Transistor Circuit Topologies.
Powering the Fan From a -12V Supply.
V DD
1
GND
Fan
offsets the -12V power sup-
*Note: Value depends on the specific application and is shown for example only.
Q
R
1
SENSE
1
off when V
TC642
+5V
GND
V
V
DD
OUT
OUT
V
OUT
is low.
R
BASE
b) Darlington Transistor Pair
12.0V
Zener
D
1
R
2.2 k
2
*
When V
increases by V
otherwise consistent with the case of fan operation
from +12V.
Q
V
1
GND
R
10 k
Fan
DD
4
*
R
OUT
Q
SENSE
2
-12V
Fan
Q
is high, the voltage at the anode of D
R
2.2
1
OUT
*
3
*
, causing Q
V
OUT
1
c) N-Channel MOSFET
to turn on. Operation is
DS21444C-page 13
TC642
V
GND
Fan
DD
R
Q
SENSE
1
1