TC664 Datasheet, PDF (1/36 Pages) Microchip Technology – SMBus™ PWM Fan Speed Controllers With Fan Fault Detection

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TC664/TC665
SMBus™ PWM Fan Speed Controllers With
Fan Fault Detection
Features
• Temperature Proportional Fan Speed for Reduced
Acoustic Noise and Longer Fan Life
• FanSense™ Protects against Fan Failure and
Eliminates the Need for 3-wire Fans
• Over Temperature Detection (TC665)
• Efficient PWM Fan Drive
• Provides RPM Data
• 2-Wire SMBus™-Compatible Interface
• Supports Any Fan Voltage
• Software Controlled Shutdown Mode for "Green"
Systems
• Supports Low Cost NTC/PTC Thermistors
• Space Saving 10-Pin MSOP Package
• Temperature Range: -40°C to +85ºC
Applications
• Personal Computers & Servers
• LCD Projectors
• Datacom & Telecom Equipment
• Fan Trays
• File Servers
• Workstations
• General Purpose Fan Speed Control
Package Type
10-Pin MSOP
V_IN 1
C_{F 2}
SCLK 3
SDA 4
GND 5
TC664
TC665
10 V_DD
9 V_OUT
8 SENSE
7 NC
6 FAULT
Description
The TC664/TC665 devices are PWM mode fan speed
controllers with FanSense technology for use with
brushless DC fans. These devices implement temper-
ature proportional fan speed control which lowers
acoustic fan noise and increases fan life. The voltage
at V_IN (Pin 1) represents temperature and is typically
provided by an external thermistor or voltage output
temperature sensor. The PWM output (V_OUT) is
adjusted between 30% and 100%, based on the volt-
age at V_IN. The PWM duty cycle can also be pro-
grammed via SMBus to allow fan speed control without
the need for an external thermistor. If V_IN is not con-
nected, the TC664/TC665 will start driving the fan at a
default duty cycle of 39.33%. See Section 4.3, "Fan
Startup", for more details).
In normal fan operation, a pulse train is present at the
SENSE pin (Pin 8). The TC664/TC665 use these
pulses to calculate the fan revolutions per minute
(RPM). The fan RPM data is used to detect a worn out,
stalled, open or unconnected fan. An RPM level below
the user-programmable threshold causes the TC664/
TC665 to assert a logic low alert signal (FAULT). The
default threshold value is 500 RPM. Also, if this condi-
tion occurs, FF (bit 0<0>) in the Status Register will also
be set to a ‘1’.
An over-temperature condition is indicated when the
voltage at V_IN exceeds 2.6 V (typical). The TC664/
TC665 devices indicate this by setting OTF(bit 5<X>) in
the Status Register to a '1'. The TC665 device also
pulls the FAULT line low during an over-temperature
condition.
The TC664/TC665 devices are available in a 10-Pin
MSOP package and consume 150 µA during opera-
tion. The devices can also enter a low-power shutdown
mode (5 µA, typ.) by setting the appropriate bit in the
Configuration Register. The operating temperature
range for these devices is -40°C to +85ºC.
SMBus is a trademark of Intel Coporation
 2002 Microchip Technology Inc.
DS21737A-page 1