TC649B datasheet(26/36 Pages) MICROCHIP

26 / 36 page

TC646B/TC648B/TC649B

DS21755B-page 26

 2003 Microchip Technology Inc.

FIGURE 5-13:

Design Example Schematic.

Bypass capacitor CVDD is added to the design to

decouple the bias voltage. This is good to have, espe-

cially when using a MOSFET as the drive device. This

helps to give a localized low-impedance source for the

current required to charge the gate capacitance of Q1.

Two other bypass capacitors (labeled as CB) were also

added to decouple the VIN and VAS nodes. These were

added simply to remove any noise present that might

cause false triggerings or PWM jitter. R5 is the pull-up

resistor for the FAULT output. The value for this resistor

is system-dependent.

FAULT

SENSE

32.4 k

Ω

GND

+12V

+5V

VDD

VIN

VAS

VOUT

RSENSE

CSENSE

1.0 µF

TC649B

Fan

0.01 µF

+5V

17.8 k

Ω

237 k

Ω

45.3k

Ω

10 k

Ω

0.1 µF

SI2302

MGSF1N02E

Panasonic®

12V, 140 mA

FBA06T12H

Thermometrics®

100 k

Ω @25°C

NHQ104B425R5

1.0 µF

3.0

Ω

CVDD

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