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  Microchip Technology Semiconductor Electronic Components Datasheet  

TC647B Datasheet

PWM Fan Speed Controllers

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M TC642B/TC647B
PWM Fan Speed Controllers With Minimum Fan Speed,
Fan Restart and FanSense™ Technology for Fault Detection
Features
• Temperature-Proportional Fan Speed for Acoustic
Noise Reduction and Longer Fan Life
• Efficient PWM Fan Drive
• 3.0V to 5.5V Supply Range:
- Fan Voltage Independent of TC642B/TC647B
Supply Voltage
- Supports any Fan Voltage
• FanSenseFault Detection Circuit Protects
Against Fan Failure and Aids System Testing
• Shutdown Mode for "Green" Systems
• Supports Low Cost NTC/PTC Thermistors
• Over-Temperature Indication (TC642B only)
• Fan Auto-Restart
• Space-Saving 8-Pin MSOP Package
Applications
• Personal Computers & Servers
• LCD Projectors
• Datacom & Telecom Equipment
• Fan Trays
• File Servers
• General Purpose Fan Speed Control
Package Types
MSOP, PDIP, SOIC
VIN
CF
VMIN
GND
1
2
3
4
TC642B
TC647B
8 VDD
7 VOUT
6 FAULT
5 SENSE
Description
The TC642B/TC647B devices are new versions of the
existing TC642/TC647 fan speed controllers. These
devices are switch mode, fan speed controllers that
incorporate a new fan auto-restart function. Tempera-
ture-proportional speed control is accomplished using
pulse width modulation. A thermistor (or other voltage
output temperature sensor) connected to the VIN input
supplies the required control voltage of 1.20V to 2.60V
(typical) for 0% to 100% PWM duty cycle. Minimum fan
speed is set by a simple resistor divider on the VMIN
input. An integrated Start-Up Timer ensures reliable
motor start-up at turn-on, coming out of shutdown
mode or following a transient fault. A logic-low applied
to VMIN (pin 3) causes fan shutdown.
The TC642B and TC647B also feature Microchip
Technology's proprietary FanSensetechnology 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 TC642B/
TC647B device to turn the VOUT output on full (100%
duty cycle). If the fault persists (a fan current pulse is
not detected within a 32/f period), the FAULT output
goes low. Even with the FAULT output low, the VOUT
output is on full during the fan fault condition in order to
attempt to restart the fan. FAULT is also asserted if the
PWM reaches 100% duty cycle (TC642B only), indicat-
ing that maximum cooling capability has been reached
and a possible overheating condition exists.
The TC642B and TC647B devices are available in 8-pin
plastic MSOP, SOIC and PDIP packages. The specified
temperature range of these devices is -40 to +85ºC.
2003 Microchip Technology Inc.
DS21756B-page 1


  Microchip Technology Semiconductor Electronic Components Datasheet  

TC647B Datasheet

PWM Fan Speed Controllers

No Preview Available !

TC642B/TC647B
Functional Block Diagram
TC642B/TC647B
VIN VOTF
Note
CF
VMIN
Clock
Generator
VSHDN
GND
VDD
Control
Logic
3TxTimPeWrM
Note: The VOTF comparator
is for the TC642B device only.
VOUT
Start-up
Timer
Missing
Pulse
Detect
10 k
70 mV
(typ)
FAULT
SENSE
DS21756B-page 2
2003 Microchip Technology Inc.


Part Number TC647B
Description PWM Fan Speed Controllers
Maker Microchip
PDF Download

TC647B Datasheet PDF






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