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TC646 Datasheet, PDF (1/28 Pages) Microchip Technology – PWM Fan Speed Controller with Auto-Shutdown and FanSense™ Technology | |||
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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, âTypical Applicationsâ, 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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