Datasheet
2002-2013 Microchip Technology Inc. DS21734B-page 1
TC654/TC655
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 (TC655)
• 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
Description
The TC654 and TC655 are PWM mode fan speed con-
trollers with FanSense technology for use with brush-
less DC fans. These devices implement temperature
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 pro-
vided by an external thermistor or voltage output tem-
perature sensor. The PWM output (V
OUT
) is adjusted
between 30% and 100%, based on the voltage at V
IN
.
The PWM duty cycle can also be programmed via
SMBus to allow fan speed control without the need for
an external thermistor. If V
IN
is not connected, the
TC654/TC655 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, pulse trains are present at
SENSE1 (Pin 8) and SENSE2 (Pin 7). The TC654/
TC655 use these pulses to calculate the fan revolu-
tions 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 TC654/TC655 to assert a logic low alert
signal (FAULT
). The default threshold value is
500 RPM. Also, if this condition occurs, F1F (bit 0<0>)
or F2F (bit 1<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 TC654/
TC655 devices indicate this by setting OTF(bit 5<X>) in
the Status Register to a '1'. The TC655 device also
pulls the FAULT
line low during an over-temperature
condition.
The TC654/TC655 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.
10-Pin MSOP
1
2
3
4
5
10
9
8
7
6
V
IN
C
F
SCLK
SDA
GND
V
DD
V
OUT
SENSE1
SENSE2
FAULT
TC654
TC655
Dual SMBus™ PWM Fan Speed Controllers With
Fan Fault Detection