DTC646 Datasheet, PDF (1/30 Pages) Microchip Technology – PWM Fan Speed Controller with Auto-Shutdown and FanSense™ Technology

DTC646
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
V_{IN 1}
C_F 2
V_{AS 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 V_IN 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 (V_IN) is below a user programmed
minimum setting (V_AS). 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 proprie-
tary FanSense™ technology for increasing system reli-
ability. 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 uncon-
nected 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 shutdown 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.
 2002-2012 Microchip Technology Inc.
DS21446D-page 1