TC649 Microchip, TC649 Datasheet - Page 16

• Manufacturer Part Number: TC649
• Description: PWM Fan Speed Controller
• Manufacturer: Microchip

TC649
5.8
In a system containing a microcontroller or other host
intelligence, the TC649 can be effectively managed as
a CPU peripheral. Routine fan control functions can be
performed by the TC649 without processor interven-
tion. The microcontroller receives temperature data
from one or more points throughout the system. It
calculates a fan operating speed based on an algorithm
specifically designed for the application at hand. The
processor controls fan speed using complementary
port bits I/O1 through I/O3. Resistors R
.
FIGURE 5-10:
FIGURE 5-11:
DS21449C-page 16
Temperature Data from
One or more Sensors
Analog or Digital
TC649 as a Microcontroller
Peripheral
+5V
TC649 as a Microcontroller Peripheral.
V
RELEASE
GND
Microcontroller
Open-Drain
Outputs
Output
CMOS
1.0
0.9
0.8
0.7
0.6
0.5
0.4
CMOS
0˚C
vs. Temperature.
V
V
V
DD
DD
DD
I/O2
I/O3
INT
I/O0
I/O1
= 4.0V
= 5.0V
= 5.5V
1
(MSB)
(LSB)
(RESET)
through R
+5V
V
360 k
1.5 k
110 k
240 k
RELEASE
R 3
R
R
TEMPERATURE
(Optional)
1
2
R
1 k
5
6
R
6
25˚C
vs. Temperature
R
18 k
4
+5V
V
(5% tolerance) form a crude 3-bit DAC that translates
this 3-bit code from the processor's outputs into a 1.6V
DC control signal. A monolithic DAC or digital pot may
be used instead of the circuit shown in Figure 5-10.
With V
when the processor's output code is 000[B]. Output
codes 001[B] to 111[B] operate the fan from roughly
40% to 100% of full speed. An open-drain output from
the processor (I/O0) can be used to reset the TC649
following detection of a fault condition. The FAULT out-
put can be connected to the processor's interrupt input
or to another I/O pin for polled operation.
18 k
DD
33 k
C B
.01 µF
R
R
= 3.0V
8
7
AS
C
.01µF
set at 1.8V, the TC649 enters auto-shutdown
B
1µF
+
1
2
3
4
V
C
V
GND
IN
AS
F
TC649
85˚C
SENSE
FAULT
V
V
OUT
2002 Microchip Technology Inc.
DD
8
7
6
5
+5V
0.1 µF
+5V
R
10 k
C
1 µF
10
800
B
R
9
+12V
Fan
2N2222A
R
2.2
11