TC642B Datasheet, PDF (1/34 Pages) Microchip Technology – PWM Fan Speed Controllers With Minimum Fan Speed, Fan Restart and FanSense™ Technology for Fault Detection

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
• FanSense^™ Fault 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
V_IN 1
C_F 2
V_MIN 3
GND 4
TC642B
TC647B
8 V_DD
7 V_OUT
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 V_IN 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 V_MIN
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 V_MIN (pin 3) causes fan shutdown.
The TC642B and TC647B also feature Microchip
Technology's proprietary 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 TC642B/
TC647B device to turn the V_OUT 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 V_OUT
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