TC647 Microchip, TC647 Datasheet - Page 13

• Manufacturer Part Number: TC647
• Description: PWM Fan Speed Controller
• Manufacturer: Microchip

FIGURE 5-6:
R
TABLE 5-2:
MMBT2222A
MPS2222A
MPS6602
SI2302
MGSF1N02E
SI4410
SI2308
Note 1: A series gate resistor may be used in order to control the MOSFET turn-on and turn-off times.
BASE
2002 Microchip Technology Inc.
Device
V
OH
.
= 80% V
DD
TRANSISTORS AND MOSFETS FOR Q
Package
SOT-23
SOT-23
SOT-23
SOT-23
TO-92
TO-92
SO-8
+ V
Circuit For Determining
R
R BASE
BASE
+ V
V
BE (SAT)
–
R SENSE
Max. V
+
–
GND
V
–
Fan
DD
R
BE(sat)
Q 1
1.2
1.2
1.2
2.5
2.5
4.5
4.5
(V)
SENSE
/V
GS
Min. H
NA
NA
NA
NA
50
50
50
positive voltage power supplies. As shown in Figure 5-8,
The correct value for this resistor can be determined as
follows:
V
“Electrical Characteristics”; V
sen transistor data sheet. It is now possible to solve for
R
EQUATION
Some applications require the fan to be powered from the
negative 12V supply to keep motor noise out of the
zener diode D
holding transistor Q
high, the voltage at the anode of D
causing Q
the case of fan operation from +12V.
FE
1
OH
BASE
(V
DD
V
is specified as 80% of V
.
V
V
V
I
CEO
BASE
OH
R
R
R
= 5V)
(V)
40
40
40
20
20
30
60
SENSE
BASE
1
BASE
to turn on. Operation is otherwise the same as
/V
DS
1
=
offsets the -12V power supply voltage,
= V
= I
= R
= I
1
V
Fan Current
off when V
OH
FAN
FAN
R
BASE
SENSE
(mA)
1000
- V
150
150
500
500
500
500
x R
/ h
BE(
x I
FE
SENSE
+ V
I
BE(
SAT
BASE
BASE
OUT
)
BE(
SAT
- V
1
is low. When V
)
SAT
DD
R
is given in the cho-
SENSE
increases by V
DS21447C-page 13
TC647
)
Suggested
+ V
R
in Section 1.0,
BASE
Note 1
Note 1
Note 1
Note 1
R
800
800
301
BASE
( )
OUT
OUT
is