TC648 データシートの表示（PDF） - Microchip Technology

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TC648

Fan Speed Controller with Auto-Shutdown and Over-Temperature Alert

Microchip Technology 

TC648

+5V

RESET

Shutdown

Open-Drain

Device

(Optional)

R1

20.5 kΩ

R2

3.83 kΩ

NTC

10 kΩ

+5V

CB

1 µF

@ 25˚C

1

VIN

CB

0.01 µF

8

VDD

4

GND

6

OTF

+5V

R5

33 kΩ

3 VAS

CB

R6 0.01 µF2

18 kΩ

CF

CB

1 µF

TC648

VOUT 7

NC 5

FIGURE 5-8:

Design Example.

Thermal

Fault

5.8 TC648 as a Microcontroller

Peripheral

In a system containing a microcontroller or other host

intelligence, the TC648 can be effectively managed as

a CPU peripheral. Routine fan control functions can be

performed by the TC648 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 R1 through R6 (5% tolerance) form a crude

3-bit DAC that translates the 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 5-9.

With VAS set at 1.8V, the TC648 enters auto-shutdown

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 TC648

following detection of a fault condition. The OTF output

can be connected to the processor's interrupt input, or

to another I/O pin, for polled operation.

+12V

Fan

Q1

R7

800Ω

 2002 Microchip Technology Inc.

DS21448C-page 15

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