TC654_14 Datasheet, PDF (1/38 Pages) Microchip Technology – Dual SMBus™ PWM Fan Speed Controllers With Fan Fault Detection

TC654/TC655
Dual 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
• Overtemperature 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 and Servers
• LCD Projectors
• Datacom and 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
TC654
TC655
10 V_DD
9 V_OUT
8 SENSE1
7 SENSE2
6 FAULT
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 Start-up” 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 2.6V (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.
 2002-2014 Microchip Technology Inc.
DS20001734C-page 1