TC647 datasheet(15/28 Pages) MICROCHIP

15 / 28 page

 2002 Microchip Technology Inc.

DS21447C-page 15

TC647

FIGURE 5-9:

Design Example.

5.8

TC647 as a Microcontroller

Peripheral

In a system containing a microcontroller or other host

intelligence, the TC647 can be effectively managed as

a CPU peripheral. Routine fan control functions can be

performed by the TC647 without controller intervention.

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 complimentary 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 controller or 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 VMIN set to 1.8V, the TC647 has a minimum

operating speed of approximately 40% of full rated

speed 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/O can be used to reset the

TC647 following detection of a fault condition. The

FAULT output can be connected to the processor's

interrupt input, or to an I/O pin, for polled operation (see

Figure 5-10).

FAULT

SENSE

NTC

10 k

Ω

@ 25

°C

20.5 k

Ω

3.83 k

Ω

33 k

Ω

800

Ω

18 k

Ω

10 k

Ω

GND

Fan Shutdown

(Optional)

+12V

+5V

VDD

VIN

VMIN

VOUT

RSENSE

2.2

Ω

CSENSE

0.1 µF

1 µF

TC647

Fan

0.01 µF

System

Fault

0.01 µF

1 µF

TC647 Datasheet(PDF) 15 Page - Microchip Technology

TC647 Datasheet(HTML) 15 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datasheet Download

Link URL