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 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

(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

The PWM duty cycle can also be programmed via

SMBus to allow fan speed control without the need for

an external thermistor. If V

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

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

SCLK

SDA

GND

OUT

SENSE1

SENSE2

FAULT

TC654

TC655

Dual SMBus™ PWM Fan Speed Controllers With

Fan Fault Detection

Summary of content (36 pages)

PAGE 1
TC654/TC655 Dual SMBus™ PWM Fan Speed Controllers With Fan Fault Detection Features Description • 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 • Spac
PAGE 2
TC654/TC655 Functional Block Diagram TC654/TC655 – VIN – VOTF + Note OTF VDD + + Control Logic VOUT Start-up Timer FAULT – CF VMIN Clock Generator Missing Pulse Detect  SCLK SDA SENSE1 – Serial Port Interface 100 mV (typ.)  GND 50 k 50 k SENSE2 – 100 mV (typ.) Note: OTF condition applies for the TC655 device only. DS21734B-page 2  2002-2013 Microchip Technology Inc.
PAGE 3
TC654/TC655 1.0 ELECTRICAL CHARACTERISTICS PIN FUNCTION TABLE Name Function Absolute Maximum Ratings * VIN Analog Input VDD..................................................................................6.5 V CF Analog Output Input Voltages .................................... -0.3 V to (VDD + 0.3 V) SCLK Serial Clock Input Output Voltages .................................. -0.3 V to (VDD + 0.3 V) SDA Serial Data In/Out (Open Drain) Storage temperature .....................................
PAGE 4
TC654/TC655 ELECTRICAL SPECIFICATIONS (CONTINUED) Electrical Characteristics: Unless otherwise noted, all limits are specified for VDD = 3.0 V to 5.5 V, -40°C
PAGE 5
TC654/TC655 SMBus Write Timing Diagram A B tLOW tHIGH C D E F G H I J K M L SCLK SDA tSU(START) tH(START) tSU-DATA tH-DATA tSU(STOP)tIDLE F = Acknowledge Bit Clocked into Master G = MSB of Data Clocked into Slave H = LSB of Data Clocked into Slave I = Slave Pulls SDA Line Low A = Start Condition B = MSB of Address Clocked into Slave C = LSB of Address Clocked into Slave D = R/W Bit Clocked into Slave E = Slave Pulls SDA Line Low J = Acknowledge Clocked into Master K = Acknowledge Clock Pu
PAGE 6
TC654/TC655 TYPICAL PERFORMANCE CURVES Note: The graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. The performance characteristics listed herein are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified operating range (e.g., outside specified power supply range) and therefore outside the warranted range. 180 14 Pins 7,8, and 9 Open 175 VOL = 0.
PAGE 7
TC654/TC655 10 50 VOL = 0.4 V 8 40 VDD = 5.5 V VDD = 5.0 V 35 30 RPM Error (%) SDA IOL (mA) CF = 1.0 µF 9 45 6 5 VDD = 3.0 V 4 3 2 VDD = 4.0 V 25 7 VDD = 5.0 V 1 VDD = 3.0 V 20 VDD = 5.5 V 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 Temperature (ºC) FIGURE 2-7: SDA IOL vs. Temperature. 65 80 95 110 125 FIGURE 2-10: Temperature. 95 110 125 RPM %error vs. 2.610 2.605 2.600 VDD = 5.0 V 2.595 2.590 VDD = 4.0 V 2.585 2.580 VDD = 3.
PAGE 8
TC654/TC655 3.0 PIN FUNCTIONS The descriptions of the pins are listed in Table 3-1. TABLE 3-1: PIN FUNCTION TABLE Name Function VIN Analog Input CF Analog Output SCLK Serial Clock Input SDA Serial Data In/Out (Open Drain) GND Ground FAULT Digital (Open Drain) Output SENSE2 Analog Input SENSE1 Analog Input VOUT Digital Output VDD Power Supply Input 3.1 Analog Input (VIN) 3.6 Analog Input (SENSE2) A voltage range of 1.62 V to 2.
PAGE 9
TC654/TC655 4.0 DEVICE OPERATION can be set to provide a predictive fan failure feature. This feature can be used to give a system warning and, in many cases, help to avoid a system thermal shutdown condition. The fan RPM data and threshold registers are available over the SMBus interface which allows for complete system control. The TC654 and TC655 devices allow you to control, monitor and communicate (via SMBus) fan speed for 2wire and 3-wire DC brushless fans.
PAGE 10
TC654/TC655 4.1 Fan Speed Control Methods T The speed of a DC brushless fan is proportional to the voltage across it. For example, if a fan’s rating is 5000 RPM at 12 V, it’s speed would be 2500 RPM at 6 V. This, of course, will not be exact, but should be close. There are two main methods for fan speed control. The first is pulse width modulation (PWM) and the second is linear. Using either method the total system power requirement to run the fan is equal.
PAGE 11
TC654/TC655 4.3 Fan Startup Often overlooked in fan speed control is the actual startup control period. When starting a fan from a nonoperating condition (fan speed is zero RPM), the desired PWM duty cycle or average fan voltage can not be applied immediately. Since the fan is at a rest position, the fan’s inertia must be overcome to get it started. The best way to accomplish this is to apply the full rated voltage to the fan for one second.
PAGE 12
TC654/TC655 This method of control allows for more sophisticated algorithms to be implemented by utilizing microcontrollers or microprocessors in the system. In this way, multiple system temperatures can be taken into account for determining the necessary fan speed. +5 V NTC Thermistor 100 k @ 25°C R1 34.8 k VIN C1 0.01 µF R2 14.7 k GND FIGURE 4-6: Network. TC654/ TC655 NTC Thermistor Sensor The second method for controlling the duty cycle of the PWM output (VOUT) is via the SMBus interface.
PAGE 13
TC654/TC655 See Section 7.4 for more details on selecting the appropriate current sense resistor and coupling capacitor values. FAN 1 FAN 2 RISO1 RISO2 VOUT SENSE1 TC654/ TC655 CSENSE1 RSENSE1 SENSE2 CSENSE2 GND FIGURE 4-7: RSENSE2 Fan Current Sensing. By selecting F1PPR (bits 2-1<01>) and F2PPR (bits 43<01>) in the Configuration Register, the TC654 and TC655 can be programmed to calculate RPM data for fans with 1, 2, 4 or 8 current pulses per rotation.
PAGE 14
TC654/TC655 When the TC654/TC655 devices are brought out of a shutdown mode by resetting SDM (bit 0<0>) in the Configuration Register, all of the registers (except for the Configuration and FAN_FAULT1 & 2 registers) assume their default power up states. The Configuration Register and the FAN_FAULT1 & 2 Registers maintain the states they were in prior to the device being put into the shutdown mode.
PAGE 15
TC654/TC655 5.0 SERIAL COMMUNICATION 5.1 SMBus 2-Wire Interface 5.1.1 DATA TRANSFER • Data transfer may be initiated only when the bus is not busy. • During data transfer, the data line must remain stable whenever the clock line is HIGH. Changes in the data line while the clock line is HIGH will be interpreted as a START or STOP condition. The TC654/TC655 support a bi-directional 2-Wire bus and data transmission protocol. The serial protocol sequencing is illustrated in Figure 1-1.
PAGE 16
TC654/TC655 The data on the line must be changed during the LOW period of the clock signal. There is one clock pulse per bit of data. Each data transfer is initiated with a START condition and terminated with a STOP condition. The number of the data bytes transferred between the START and STOP conditions is determined by the master device and is unlimited. 5.1.7 period of the acknowledge related clock pulse. Setup and hold times must be taken into account.
PAGE 17
TC654/TC655 6.0 REGISTER SET The TC654/TC655 devices contain 9 registers that provide a variety of data and functionality control to the outside system. These registers are listed below in TABLE 6-1: Table 6-1. Of key importance is the command byte information, which is needed in the read and write protocols in order to select the individual registers.
PAGE 18
TC654/TC655 6.2 FAN_FAULT1 & FAN_FAULT2 Threshold Registers (FAN_FAULT1 & FAN_ FAULT2) in RPM1 and RPM2 Registers) drops below the value that is set in the Fan Fault Registers for more than 2.4sec, a fan fault indication will be given. F1F (bit 0<0>) and F2F (bit 1<0>) in the Status Register indicate fan fault conditions for fan 1 and fan 2, respectively. The FAULT output will also be pulled low in a fan fault condition.
PAGE 19
TC654/TC655 6.3 CONFIGURATION REGISTER (CONFIG) The Configuration Register is an 8-bit read/writable multi-function control register. This register allows the user to clear fan faults, select RPM resolution, select REGISTER 6-3: VOUT duty cycle (fan speed) control method, select the fan current pulses per rotation for fans 1 & 2 (for fan RPM calculation) and put the TC654/TC655 device into a shutdown mode to save power consumption. See Register 6-3 below for the Configuration Register bit descriptions.
PAGE 20
TC654/TC655 6.4 STATUS REGISTER (STATUS) The Status Register provides all the information about what is going on within the TC654/TC655 devices. Fan fault information, VIN status, RPM counter overflow, REGISTER 6-4: and over temperature indication are all available in the Status Register. The Status Register is an 8-bit Read only register with bits 6 and 7 unused. See Register 64 below for the bit descriptions.
PAGE 21
TC654/TC655 6.5 DUTY-CYCLE Register (DUTY_CYCLE) The DUTY_CYCLE register is a 4-bit read/writable register used to control the duty cycle of the VOUT output. The controllable duty cycle range via this register is 30% to 100%, with programming steps of 4.67%.This method of duty cycle control is mainly used with the SMBus interface.
PAGE 22
TC654/TC655 7.0 APPLICATIONS INFORMATION 7.1 Connecting to the SMBus SDA SCLK PIC16F876 Microcontroller The SMBus is an open collector bus, requiring pull-up resistors connected to the SDA and SCLK lines. This configuration is shown in Figure 7-1. 24LC01 EEPROM TC654/TC655 Fan Speed Controller PIC® Microcontroller VDD R R SDA SCLK FIGURE 7-2: Range for R: 13.2 kto 46 k for VDD = 5.0 V FIGURE 7-1: SMBus.
PAGE 23
TC654/TC655 Temperature Sensor Design As discussed in previous sections, the VIN analog input has a range of 1.62 V to 2.6 V (typical), which represents a duty cycle range on the VOUT output of 30% to 100%, respectively. The VIN voltages can be thought of as representing temperatures. The 1.62 V level is the low temperature at which the system only requires 30% fan speed for proper cooling. The 2.6 V level is the high temperature, for which the system needs maximum cooling capability.
PAGE 24
TC654/TC655 7.4 FanSense Network (RSENSE & CSENSE) The network comprised of RSENSE and CSENSE allows the TC654/TC655 devices to detect commutation of the fan motor. RSENSE converts the fan current into a voltage. CSENSE AC couples this voltage signal to the SENSE pins (SENSE1 & SENSE2). The goal of the SENSE network is to provide a voltage pulse to the SENSE pin that has a minimum amplitude of 120 mV.
PAGE 25
TC654/TC655 MOSFETs are very low, the TC654/TC655 can charge and discharge them very quickly, leading to very fast edges. Of key concern is the turn-off edge of the MOSFET. Since the fan motor winding is essentially an inductor, once the MOSFET is turned off, the current that was flowing through the motor wants to continue to flow.
PAGE 26
TC654/TC655 The first piece of information required is the fan's full speed RPM rating. The fan RPM rating can then be converted to give the time for one revolution using the following equation: FAN EQUATION 60  1000 Time for one revolution (msec.) = -----------------------Fan RPM Q1 The fan current can now be monitored over this time period. The number of pulses occurring in this time period is the fan's "Current Pulses per Rotation" rating which is needed in order to accurately read fan RPM.
PAGE 27
TC654/TC655 Figure 7-10 shows the voltage pulse at the Sense pin, which is caused by the fan's "extra" current pulse during PWM output turn-on. FAN 1 FAN 2 RISO1 CSLOW1 (0.1uF typical) RISO2 VOUT Sense Pin Voltage "Extra Pulse" CSLOW2 SENSE1 TC654/ TC655 CSENSE (0.1 µF typical) (0.1 µF typical) RSENSE1 SENSE2 VOUT PWM FIGURE 7-10: Extra Pulse at Sense Pin. This problem occurs mainly with fans that have a current waveshape like the one shown in Figure 7-9.
PAGE 28
TC654/TC655 8.0 PACKAGING INFORMATION 8.1 Package Marking Information 10-Pin MSOP Device 1 2 3 Legend: XX...X Y YY WW NNN e3 * Note: DS21734B-page 28 10 TC654E TC655E YWWNNN 9 8 4 7 5 6 Customer-specific information Year code (last digit of calendar year) Year code (last 2 digits of calendar year) Week code (week of January 1 is week ‘01’) Alphanumeric traceability code Pb-free JEDEC designator for Matte Tin (Sn) This package is Pb-free.
PAGE 29
TC654/TC655 8.2 Taping Form Component Taping Orientation for 10-Pin MSOP Devices User Direction of Feed PIN 1 W P Standard Reel Component Orientation for TR Suffix Device Carrier Tape, Number of Components Per Reel and Reel Size: Package Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size 12 mm 8 mm 2500 13 in. 10-Pin MSOP 8.3 Package Information Note: For the most current package drawings, please see the Microchip Packaging Specification located at http://www.microchip.
PAGE 30
TC654/TC655 9.0 REVISON HISTORY Revision B (January 2013) Added a note to the package outline drawing. DS21734B-page 30  2002-2013 Microchip Technology Inc.
PAGE 31
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PAGE 32
READER RESPONSE It is our intention to provide you with the best documentation possible to ensure successful use of your Microchip product. If you wish to provide your comments on organization, clarity, subject matter, and ways in which our documentation can better serve you, please FAX your comments to the Technical Publications Manager at (480) 792-4150. Please list the following information, and use this outline to provide us with your comments about this document.
PAGE 33
TC654/TC655 PRODUCT IDENTIFICATION SYSTEM To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office. PART NO.
PAGE 34
TC654/TC655 NOTES: DS21734B-page 34  2002-2013 Microchip Technology Inc.
PAGE 35
Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature.
PAGE 36
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