TC646 View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

TC646

PWM Fan Speed Controller with Auto-Shutdown and FanSense™ Technology

Microchip Technology 

M

TC646

PWM Fan Speed Controller with Auto-Shutdown

and FanSense™ Technology

Features

• Temperature Proportional Fan Speed for Acoustic

Control and Longer Fan Life

• Efficient PWM Fan Drive

• 3.0V to 5.5V Supply Range:

- Fan Voltage Independent of TC646

Supply Voltage

- Supports any Fan Voltage

• FanSense™ Fault Detection Circuits Protect

Against Fan Failure and Aid System Testing

• Shutdown Mode for "Green" Systems

• Supports Low Cost NTC/PTC Thermistors

• Space Saving 8-Pin MSOP Package

• Over-temperature Indication

Applications

• Power Supplies

• Computers

• File Servers

• Portable Computers

• Telecom Equipment

• UPS, Power Amps

• General Purpose Fan Speed Control

Available Tools

• Fan Controller Demonstration Board (TC642DEMO)

• Fan Controller Evaluation Kit (TC642EV)

Package Types

SOIC/PDIP/MSOP

VIN 1

CF 2

VAS 3

GND 4

TC646

8 VDD

7 VOUT

6 FAULT

5 SENSE

General Description

The TC646 is a switch mode, fan speed controller for

use with brushless DC fans. Temperature proportional

speed control is accomplished using pulse width mod-

ulation (PWM). A thermistor (or other voltage output

temperature sensor) connected to the VIN input fur-

nishes the required control voltage of 1.25V to 2.65V

(typical) for 0% to 100% PWM duty cycle. The TC646

automatically suspends fan operation when measured

temperature (VIN) is below a user programmed

minimum setting (VAS). An integrated Start-up Timer

ensures reliable motor start-up at turn-on, coming out

of shutdown mode, auto-shutdown mode or following a

transient fault.

The TC646 features Microchip Technology's propri-

etary FanSense™ technology for increasing system

reliability. In normal fan operation, a pulse train is

present at SENSE (Pin 5). A missing-pulse detector

monitors this pin during fan operation. A stalled, open,

or unconnected fan causes the TC646 to trigger its

Start-up Timer once. If the fault persists, the FAULT

output goes low and the device is latched in its shut-

down mode. FAULT is also asserted if the PWM

reaches 100% duty cycle, indicating a possible thermal

runaway situation, although the fan continues to run.

See Section 5.0, “Typical Applications”, for more

information and system design guidelines.

The TC646 is available in the 8-pin plastic DIP, SOIC

and MSOP packages and is available in the industrial

and extended commercial temperature ranges.

 2002 Microchip Technology Inc.

DS21446C-page 1

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