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19-2865; Rev 1; 12/03
Temperature Monitors and PWM Fan Controllers
General Description
The MAX6653/MAX6663/MAX6664 are ACPI-compliant local and remote-junction temperature sensors and fan controllers. These devices measure their own die temperature, as well as the temperature of a remote-PN junction and control the speed of a DC cooling fan based on the measured temperature. Remote temperature measurement accuracy is 1C from +60C to +100C. Temperature measurement resolution is 0.125C for both local and remote temperatures. Internal watchdog set points are provided for both local and remote temperatures. There are two comparison set points for local temperatures and two for remote temperatures. When a set point is crossed, the MAX6653/MAX6663/MAX6664 assert either the INT or THERM outputs. These outputs can be used as interrupts, clock throttle signals, or overtemperature shutdown signals. Two pins on the MAX6653 control the power-up values of the comparison set points, providing fail-safe protection even when the system is unable to program the trip temperatures. The MAX6653 has two additional shutdown outputs, SDR and SDL, that are triggered when the remote or local temperatures exceed the programmed shutdown set points. The INT output for the MAX6653/MAX6663 and THERM outputs for the MAX6653/MAX6663/MAX6664 can also function as inputs if either is pulled low to force the fan to full speed, unless this function is masked by the user. The MAX6653/MAX6663/MAX6664 are available in 16-pin QSOP packages and operate over the -40C to +125C temperature range.
Features
o Remote-Junction Temperature Sensor Within 1C Accuracy (+60C to +100C) o ACPI-Compatible Programmable Temperature Alarms o 0.125C Resolution Local and Remote-Junction Temperature Measurement o Programmable Temperature Offset for System Calibration o SMBus 2-Wire Serial Interface with Timeout o Automatic or Manual Fan-Speed Control o PWM Fan Control Output o Fan-Speed Monitoring and Watchdog o Fan Fault and Failure Indicators o Compatible with 2-Wire or 3-Wire Fans (Tachometer Output) o +3V to +5.5V Supply Range o Additional Shutdown Set Point (MAX6653) o Controlled PWM Rise/Fall Times
MAX6653/MAX6663/MAX6664
Ordering Information
PART MAX6653AEE MAX6663AEE MAX6664AEE TEMP RANGE -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 16 QSOP 16 QSOP 16 QSOP
Applications
Personal Computers Servers Workstations Telecom Equipment Networking Equipment Test Equipment Industrial Controls
TOP VIEW
PWM_OUT 1 TACH/AIN 2 CRT0 3 CRT1 4 GND 5 VCC 6 THERM 7 FAN_FAULT 8
Pin Configurations
16 SMBCLK 15 SMBDATA 14 INT
MAX6653
13 ADD 12 SDR 11 SDL 10 DXP 9 DXN
Typical Operating Circuits appear at end of data sheet. Functional Diagram appears at end of data sheet.
QSOP
Pin Configurations continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1
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Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
ABSOLUTE MAXIMUM RATINGS
All Voltages Are Referenced to GND TACH/AIN ..............................................................-0.3V to +5.5V VCC ...........................................................................-0.3V to +6V DXP, ADD, CRIT0, CRIT1........................-0.3V to + (VCC + 0.3V) DXN .......................................................................-0.3V to +0.8V SMBDATA, SMBCLK, INT, THERM, FAN_FAULT, SDL, SDR............................................-0.3V to +6V SMBDATA, INT, THERM, FAN_FAULT, PWM_OUT Current..............................................-1mA to +50mA DXN Current .......................................................................1mA ESD Protection (all pins, Human Body Model) ..................2000V Continuous Power Dissipation (TA = +70C) 16-Pin QSOP (derate 8.3 mW/C above +70C)..........667mW Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +165C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = +3.0V to +5.5V, TA = 0C to +125C, unless otherwise noted. Typical values are at VCC = +3.3V, TA = +25C.) (Note1)
PARAMETER Operating Supply Voltage Range Standby Current Operating Current Average Operating Current IS SYMBOL VCC SMBDAT = SMBCLK = 1, register 00h = 00h SMBDAT = SMBCLK = 1 Conversion rate = 4Hz (default) VCC = +3.3V, TA = 0C to +100C, +60C TR +100C VCC = +3.3V, 0C TR +100C VCC = +3.3V, -25C TR +125C Internal Temperature Error Temperature Resolution (Internal and External) Fan TACHOMETER Accuracy Fan TACHOMETER Full-Scale Count Divisor = 1, fan count = 153 TACHOMETER Nominal Input RPM Internal Clock Frequency TACHOMETER Conversion Cycle Time Divisor = 2, fan count = 153 Divisor = 4, fan count = 153 Divisor = 8, fan count = 153 254 (Note 2) 255 4400 2200 1100 550 270 637 286 kHz ms RPM VCC = +3.3V, 0C TA +100C VCC = +3.3V, -40C TA +125C 0.125 11 6 0.5 150 CONDITIONS MIN 3.0 TYP MAX 5.5 10 1 300 1 3 4 2 4 C C Bits % C UNITS V A mA A
External Temperature Error
2
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Temperature Monitors and PWM Fan Controllers
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3.0V to +5.5V, TA = 0C to +125C, unless otherwise noted. Typical values are at VCC = +3.3V, TA = +25C.) (Note1)
PARAMETER Temperature Conversion Time Conversion Rate Timing Error Remote-Diode Sourcing Current DXN Source Voltage TACHOMETER Input Hysteresis Output Low Voltage (Sink Current) VOL SDL, SDR, THERM, FAN_FAULT, SMBDATA, PWM_OUT, VCC = +3V, IOUT = 6mA, INT, VCC = +3V, IOUT = 4mA INT, SDL, SDR, THERM, FAN_FAULT, SMBDATA, PWM_OUT SMBDATA, SMBCLK, INT, THERM, TACH/AIN SMBDATA, SMBCLK, INT, THERM, TACH/AIN 3.0V 5.5V 2.2 2.6 1 5 (Note 2) 10% to 10% (Note 2) 90% to 90% (Note 2) (Note 2) 90% of SMBCLK to 90% of SMBDATA (Note 2) 10% of SMBDATA to 10% of SMBCLK (Note 2) 90% of SMBCLK to 10% of SMBDATA (Note 2) 10% of SMBDATA to 10% of SMBCLK (Note 2) 10% of SMBCLK to 10% of SMBDATA (Note 2) (Note 2) (Note 2) 29 37 10 4 4.7 4.7 4.7 4 4 250 300 300 1000 45 100 (Note 2) High level Low level 25 80 8 100 10 0.7 100 0.4 SYMBOL CONDITIONS MIN TYP 250 25 120 12 MAX UNITS ms % A V mV V
MAX6653/MAX6663/MAX6664
Output High Leakage Current Logic Low Input Voltage Logic High Input Voltage Input Leakage Current Input Capacitance SMBus TIMING Serial Clock Frequency Clock Low Period Clock High Period Bus Free Time Between Stop and Start Condition SMBus Start Condition Setup Time Start Condition Hold Time Stop Condition Setup Time Data Setup Time Data Hold Time SMBus Fall Time SMBus Rise Time SMBus Timeout
IOH VIL VIH ILEAK CIN fSCLK tLOW tHIGH tBUF tSU:STA tHD:STO tSU:STO tSU:DAT tHD:DAT tF tR
1 0.8
A V V A pF kHz s s s s s s ns ns ns ns ms
SMBDATA, SMBCLK, INT, THERM; VIN = VCC or GND
Note 1: Tested at Values through the temperature range are guaranteed by design. Note 2: Not production tested, guaranteed by design.
+85oC.
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Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
REMOTE TEMPERATURE ERROR vs. REMOTE-DIODE TEMPERATURE
1.5 TEMPERATURE ERROR (C) 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 0 1 2 3 4 -40 -25 -10 5 20 35 50 65 80 95 110 125 REMOTE-DIODE TEMPERATURE (C) CONVERSION RATE (Hz)
MAX6653 toc03
STANDBY SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX6653 toc01
AVERAGE OPERATING SUPPLY CURRENT vs. CONVERSION RATE
450 400 SUPPLY CURRENT (A) 350 300 250 200 150 100 50
MAX6653 toc02
5.0 STANDBY SUPPLY CURRENT (A) 4.5 4.0 3.5 3.0 2.5 2.0 3.0 3.5 4.0 4.5 5.0
500
2.0
0 5.5 SUPPLY VOLTAGE (V)
LOCAL TEMPERATURE ERROR vs. DIE TEMPERATURE
MAX6653 toc04
REMOTE TEMPERATURE ERROR vs. POWER-SUPPLY NOISE FREQUENCY
MAX6653 toc05
LOCAL TEMPERATURE ERROR vs. POWER-SUPPLY NOISE FREQUENCY
REMOTE TEMPERATURE ERROR (C) 6 5 4 3 2 1 100mVP-P 0 -1 -2 250mVP-P
MAX6653 toc06
2.0 LOCAL TEMPERATURE ERROR (C) 1.5 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0
10 REMOTE TEMPERATURE ERROR (C) 9 8 7 6 5 4 3 2 1 0 100mVP-P 250mVP-P
7
-40 -25 -10 5 20 35 50 65 80 95 110 125 DIE TEMPERATURE (C)
0.001
0.01
0.1
1
10
100
0.001
0.01
0.1
1
10
100
POWER-SUPPLY NOISE FREQUENCY (MHz)
POWER-SUPPLY NOISE FREQUENCY (MHz)
TEMPERATURE ERROR vs. COMMON-MODE NOISE FREQUENCY
MAX6653 toc07
TEMPERATURE ERROR vs. DIFFERENTIAL-MODE NOISE FREQUENCY
MAX6653 toc08
TEMPERATURE ERROR vs. DXP-DXN CAPACITANCE
MAX6653 toc09
12 10 TEMPERATURE ERROR (C) 8 6 4 2 0 -2 0.0001 0.001 20mVP-P 40mVP-P
8 7 TEMPERATURE ERROR (C) 6 5 4 3 2 1 0 20mVP-P 30mVP-P
1 0 TEMPERATURE ERROR (C) -1 -2 -3 -4 -5
0.01
0.1
1
10
100
0.01
0.1
1
10
100
1
10 DXP-DXN CAPACITANCE (nF)
100
COMMON-MODE NOISE FREQUENCY (MHz)
DIFFERENTIAL-MODE NOISE FREQUENCY (MHz)
4
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Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Pin Description
PIN MAX6653 QSOP 1 2 3 4 -- 5 6 MAX6663/ MAX6664 QSOP 1 2 -- -- 3, 4 5 6 NAME FUNCTION
PWM_OUT TACH/AIN CRIT0 CRIT1 N.C. GND VCC
Digital Output (Open Drain). Pulse-width modulated output to external power transistor. Requires a pullup resistor (10k typ). Digital/Analog Input. Fan tachometer input. May be reprogrammed as an analog input to measure speed of a 2-wire fan. See Figure 5. Input. Used in conjunction with CRIT1 to set THERM and SHUTDOWN default set points (see Table 1). Input. Used in conjunction with CRIT0 to set THERM and SHUTDOWN default set points (see Table 1). No Connection. Not internally connected. Ground Power Supply. Bypass with a 0.01F capacitor to GND. Digital I/O (Open Drain). An active-low thermal-overload output to indicate that the overtemperature set point has been exceeded. Also acts as an input to provide external fan control. When this pin is pulled low by an external signal, a status bit is set and the fan speed is forced full-on. Requires a pullup resistor (10k typ). Digital Output (Active Low, Open Drain). Signals a fan fault. Requires a pullup resistor (10k typ). Combined Current Sink and A/D Negative Input. DXN is internally biased to a diode voltage above ground. Combined Current Source and A/D Positive Input for the Remote-Diode Channel. Do not leave DXP floating; connect DXP to DXN if no remote diode is used. Place a 2200pF capacitor between DXP and DXN for noise filtering. An Active-Low Open-Drain Output. It indicates that local temperature is above the shutdown set point. Normally used to directly deactivate the CPU power supply. An Active-Low Open-Drain Output. It indicates that remote temperature is above the shutdown set point. Normally used to directly deactivate the CPU power supply. Internal Connection. Leave floating or connect to GND. Three-State Logic Input. Sets the 2 lower bits of the device SMBus address (Table 2). ADD is not an ordinary logic input pin; ADD should be connected to VCC, GND, or float. Digital Output (Open Drain). Can be programmed as an interrupt output for temperature/fan speed interrupts. Requires a pullup resistor (10k typ). For the MAX6653/MAX6663, it can be used also as an input. If pulled low, fan speed is forced to maximum unless masked. SMBus Serial-Data Input/Output (Open Drain). Requires a pullup resistor (10k typ). SMBus Serial-Clock Input. Requires a pullup resistor (10k typ). Internal Connection. Leave floating or connect to GND.
7
7
THERM
8 9
8 9
FAN_FAULT DXN
10
10
DXP
11 12 -- 13
-- -- 11, 12 13
SDL SDR N.C. ADD
14
14
INT
15 16 --
15 16 12
SMBDATA SMBCLK N.C.
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Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Table 1. MAX6653 Power-Up Set-Point Decoding
CRIT1 GND GND GND Open Open Open VCC VCC VCC CRIT0 Open GND VCC Open GND VCC Open GND VCC THERM SET POINT (C) REMOTE 85 90 95 100 105 110 115 120 125 LOCAL 55 60 65 70 75 80 85 90 95 SHUTDOWN SET POINT (C) REMOTE 110 115 120 125 125 125 125 125 125 LOCAL 80 85 90 95 95 95 95 95 95
Detailed Description
The MAX6653/MAX6663/MAX6664 are local/remote temperature monitors and fan controllers for microprocessor-based systems. These devices communicate with the system through a serial SMBus interface. The serial bus controller features a hard-wired address pin for device selection, an input line for a serial clock, and a serial line for reading and writing addresses and data (see Functional Diagram). The MAX6653/MAX6663/MAX6664 fan control section can operate in three modes. In the automatic fan-control mode, the fan's power-supply voltage is automatically adjusted based on temperature. The control algorithm parameters are programmable to allow optimization to the characteristics of the fan and the system. RPM select mode forces the fan speed to a programmed tachometer value. PWM duty cycle select mode allows user selection of the PWM duty cycle. PWM rise and fall times are limited to maximize fan reliability. To ensure overall system reliability, the MAX6653/ MAX6663/MAX6664 feature an SMBus timeout so that the MAX6653/MAX6663/MAX6664 can never "lock" the SMBus. Furthermore, the availability of hard-wired default values for critical temperature set points ensures the MAX6653 controls critical temperature events properly even if the SMBus is "locked" by some other device on the bus.
(Table 2) and, therefore, a maximum of three MAX6653/ MAX6663/MAX6664 devices can share the same bus. The MAX6653/MAX6663/MAX6664 employ four standard SMBus protocols: Write Byte, Read Byte, Send Byte, and Receive Byte (Figures 1, 2, and 3). The shorter Receive Byte protocol allows quicker transfers, provided that the correct data register was previously selected by a Read Byte instruction. Use caution with the shorter protocols in multimaster systems, since a second master could overwrite the command byte without informing the first master.
Alert Response Address
The MAX6653/MAX6663/MAX6664 respond to the SMBus alert response address, an event which typically occurs after an SMBus host master detects an INT interrupt signal going active (referred to as ALERT in SMBus nomenclature). When the host master puts the alert response address (0001 1001) on the bus, all devices with an active INT output respond by putting their own address onto the bus. The alert response can activate several different slave devices simultaneously, similar to the I2C general call. If more than one slave attempts to respond, bus arbitration rules apply, and the device with the lowest address code wins. The master then services the devices from the lowest address up.
SMBus Digital Interface
From a software perspective, the MAX6653/MAX6663/ MAX6664 appear as a set of byte-wide registers. These devices use a standard SMBus 2-wire/I2C-compatible serial interface to access the internal registers. The MAX6653/MAX6663/MAX6664 slave address can be set to three different values by the input pin ADD
6
Table 2. MAX6653/MAX6663/MAX6664 Slave Address Decoding
ADD PIN GND No connect VCC ADDRESS 0101 100 0101 110 0101 101
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Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Write Byte Format S ADDRESS 7 bits Slave Address: equivalent to chip-select line of a 3-wire interface Read Byte Format S ADDRESS 7 bits Slave Address: equivalent to chip-select line WR ACK COMMAND 8 bits Command Byte: selects which register you are reading from ACK S ADDRESS 7 bits Slave Address: repeated due to change in dataflow direction Receive Byte Format ACK COMMAND 8 bits Data Byte: writes data to the register commanded by the last read byte or write byte transmission S = Start condition P = Stop condition Shaded = Slave transmission / / / = Not acknowledged ACK P S ADDRESS 7 bits RD ACK DATA 8 bits Data Byte: reads data from the register commanded by the last read byte or write byte transmission; also used for SMBus alert response return address /// P RD ACK DATA 8 bits Data Byte: reads from the register set by the command byte /// P WR ACK COMMAND 8 bits Command Byte: selects which register you are writing to ACK DATA 8 bits Data Byte: data goes into the register set by the co mma nd byte ( to se t thresholds, configuration masks, and sampling rate) ACK P
Send Byte Format S ADDRESS 7 bits WR
Figure 1. SMBus Protocols
A
tLOW
B
tHIGH
C
D
E
F
G
H
I
J
K
L
M
SMBCLK
SMBDATA
tSU:STA
tHD:STA
tSU:DAT
tHD:DAT
tSU:STO tBUF
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 SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO SLAVE H = LSB OF DATA CLOCKED INTO SLAVE I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION, DATA EXECUTED BY SLAVE M = NEW START CONDITION
Figure 2. SMBus Write Timing Diagram
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Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
A tLOW B tHIGH C D E F G H I J K L M
SMBCLK
SMBDATA
tSU:STA
tHD:STA
tSU:DAT
tHD:DAT F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO MASTER H = LSB OF DATA CLOCKED INTO MASTER I = MASTER PULLS DATA LINE LOW
tSU:STO tBUF J = ACKNOWLEDGE CLOCKED INTO SLAVE K = ACKNOWLEDGE CLEAR PULSE L = STOP CONDITION, EXECUTED BY SLAVE M = NEW START CONDITION
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 SMBDATA LINE LOW
Figure 3. SMBus Read Timing Diagram
The MAX6663 resets its INT output and some of the status bits in the status register after responding to an alert response address; however, if the error condition that caused the interrupt is still present, INT is reasserted on the next monitoring cycle. INT is maskable to allow full control of ALERT conditions.
Temperature Measurement
The MAX6653/MAX6663/MAX6664 contain on-chip temperature sensors to sense their own die (local) temperatures. These devices can also measure remote temperatures such as the die temperature of CPUs or other ICs having on-chip temperature-sensing diodes, or discrete diode-connected transistors as shown in the Typical Operating Circuits. For best accuracy, the discrete diode-connected transistor should be a small-signal device with its collector and base connected together. The on-chip ADC converts the sensed temperature and outputs the temperature data in the format shown in Tables 3 and 4. The temperature measurement resolution is 0.125C for both local and remote temperatures. The temperature accuracy is within 1C for remote temperature measurements from +60C to +100C. The Local Temperature Offset (0Dh) and Remote Temperature Offset (0Eh) registers allow the measured temperature to be increased or decreased by a fixed value to compensate for errors due to variations in diode resistance and ideality factor (see the Remote Diode Considerations section). The reported temperature is the measured temperature plus the correction value. Both the measured temperature and the reported value are limited by the sensor's temperature range. For example, if a remote thermal diode is being measured and its temperature is 135C, the measured temperature is the maximum
value of 127.875C. If the remote offset value is set to 10C, the reported value is 117.875C, not 125C. The temperature conversion rate is programmable using bits [4:2] of the fan filter register (23h) as shown in Table 5. The DXN input is biased at 0.65V above ground by an internal diode to set up the analog-to-digital inputs for a differential measurement. The worst-case DXP-DXN differential input voltage range is from 0.25V to 0.95V. Excess resistance in series with the remote diode causes about 0.5C error per ohm. Likewise, a 200V offset voltage forced on DXP-DXN causes about 1C error. High-frequency EMI is best filtered at DXP and DXN with an external 2200pF capacitor. This value can be increased to about 3300pF, including cable capacitance. Capacitance higher than 3300pF introduces errors due to the rise time of the switched current source.
Table 3. Temperature Data High Byte Format
TEMP (C) 130.00 127.00 126.00 25.25 0.50 0.00 -1 -125 -128 Diode fault (short or open) DIGITAL OUTPUT (C) +127 +127 +126 +25 0 0 -- -- -- -- DIGITAL OUTPUT (BINARY) 0111 1111 0111 1111 0111 1110 0001 1001 0000 0000 0000 0000 1111 1111 1000 0011 1000 0000 1000 0000
8
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Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Table 4. Temperature Data Low Byte Format Structure: LLLXXRRR*
FRACTIONAL TEMPERATURE (C) 0.000 0.125 0.25 0.375 0.5 0.625 0.75 0.875 DIGITAL OUTPUT (LOCAL) 000X XXXX 001X XXXX 010X XXXX 011X XXXX 100X XXXX 101X XXXX 110X XXXX 111X XXXX DIGITAL OUTPUT (REMOTE) XXX XX 000 XXX XX 001 XXX XX 010 XXX XX 011 XXX XX 100 XXX XX 101 XXX XX 110 XXX XX 111
*Where: LLL = local fractional temperature bits, XX = don't care, RRR = remote fractional temperature bits.
Table 5. Temperature Conversion Rate Setting (Fan Filter Register (23h)--POR = 111)
BIT 4 0 0 0 0 1 1 1 1 BIT 3 0 0 1 1 0 0 1 1 BIT2 0 1 0 1 0 1 0 1 CONVERSION RATE (Hz) 0.0625 0.125 0.25 0.5 1 2 4 4 CONVERSION TIME (s) 16 8 4 2 1 0.5 0.25 0.25
Table 6. Threshold Limit Registers
NAME LTH LTL LTHER RTH RTL RTHER LTSD RTSD ADDRESS 14h 15h 16h 18h 19h 1Ah 1Bh 1Ch R/W R/W R/W R/W R/W R/W R/W R/W R/W MAX6653 POR VALUE Set by CRIT0 and CRIT1 Set by CRIT0 and CRIT1 Set by CRIT0 and CRIT1 Set by CRIT0 and CRIT1 Set by CRIT0 and CRIT1 Set by CRIT0 and CRIT1 Set by CRIT0 and CRIT1 Set by CRIT0 and CRIT1 MAX6663/MAX6664 POR STATE 0011 1100 0000 0000 0100 0110 0101 0000 0000 0000 0110 0100 N/A N/A DESCRIPTION Local temp high limit Local temp low limit Local temp THERM limit Remote temp high limit Remote temp low limit Remote temp THERM limit Local temp shutdown limit (MAX6653 only) Remote temp shutdown limit (MAX6653 only)
Temperature Comparison and Interrupt System
At the end of each conversion cycle, the converted temperature data are compared to various set-point thresholds to control the INT, THERM, SDL, and SDR outputs. All temperature threshold limits are stored in the threshold limit registers (Table 6) and can be changed through the SMBus digital interface.
THERM is an active-low thermal-overload output indicating that the THERM overtemperature set point is exceeded. With the THERM threshold set to an appropriate value, the THERM output can be used to control clock throttling. When this pin is pulled low by an external signal, a status bit (bit 7, status register 2) is set, and the fan speed is unconditionally forced to full-on speed. The only way to reset the status bit is to read status register 2. Connect a 10k pullup resistor between THERM and VCC.
9
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Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
INT is an open-drain digital output that reports the status of temperature interrupt limits and fan out-of-limit conditions. Set bit 1 of configuration register 1 (00h) to 1 to enable INT output or reset this bit to zero to disable the INT output function. Status register 1 contains status information for the conditions that cause INT to assert. Reading status register 1 resets INT, but INT is reasserted if the fault condition still exists. Connect a 10k pullup resistor between INT and VCC. SDL and SDR are open-drain digital outputs on the MAX6653 that can be used to shut the system down based on the local (die) temperature of the MAX6653 or the temperature of the remote sensor, respectively. The trip thresholds for SDL and SDR are normally set above the THERM and INT limits. Their power-up values are set by the CRIT1 and CRIT0 pins, as shown in Table 1. RPM Select Fan-Control Mode In RPM select mode, the MAX6653/MAX6663/MAX6664 adjust their PWM output duty cycle to match a selected fan speed measured by a tachometer count value. Before selecting this mode by setting bits [7:5] of configuration register 1 (00h) to 0x1, the desired tachometer count value should be written to the fan tachometer high-limit register (10h). In this mode, the MAX6653/MAX6663/ MAX6664 are not able to detect underspeed fan faults because the fan tachometer high-limit register (10h) functions as the target tachometer count. The MAX6653/MAX6663/MAX6664 detect fan stall faults by comparing the fan-speed reading to the fullscale constant of 254 (FEh). Therefore, the MAX6653/MAX6663/MAX6664 signal a fan fault when the fan-speed reading is 255 (FFh). Note that the RPM mode cannot be used for speeds below 10% of the fan's maximum speed. It is important to verify that a fan works properly at lower RPM values if a low-RPM operation in this mode is desired.
Fan-Speed Control
The MAX6653/MAX6663/MAX6664 fan-control section can operate in one of three modes depending on the setting of bit 7 to bit 5 of configuration register 1 (00h). Regardless of the mode of operation, the PWM output frequency is programmable, and the fan speed is measured with the result stored in the fan-speed register (08h). PWM Output Frequency The PWM output frequency is programmed by bit 5, bit 4, and bit 3 of the fan characteristics register (20h), regardless of the mode of operation. See Table 7. Fan-Control Mode The mode of fan-speed control operation is set by bit 7, bit 6, and bit 5 in configuration register 1 (00h), as shown in Table 8. PWM Duty-Cycle Fan-Control Mode Bits [3:0] of the fan-speed configuration register set the PWM duty cycle. See Table 9 for more details.
Table 7. Setting PWM Output Frequency
FAN CHARACTERISTICS REGISTER (20H) POR = 011 BIT 5 0 0 0 0 1 1 1 1 BIT 4 0 0 1 1 0 0 1 1 BIT 3 0 1 0 1 0 1 0 1 PWM FREQUENCY (Hz) 11.7 15.6 23.4 31.25 37.5 46.9 62.5 93.5
Table 8. Setting the Fan-Speed Control Mode (Default = 100)
Bits [7:5] 0x0 MODE OF OPERATION PWM duty-cycle mode DESCRIPTION Directly program the PWM duty cycle by writing to bits [3:0] of the fan-speed configuration register (22h). Program the desired fan speed by writing to the fan tachometer high-limit register (10h). This value should be written after selecting the RPM mode. The MAX6653/MAX6663/MAX6664 then adjust the PWM duty cycle to cause the fan to spin at the programmed speed. PWM duty cycle is automatically controlled by the remote temperature. PWM duty cycle is automatically controlled by both the remote and the local temperatures. See the Automatic Fan-Control Mode section.
0x1
RPM select mode
100 111
Automatic mode Automatic mode
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Temperature Monitors and PWM Fan Controllers
Table 9. Setting PWM Duty Cycle
BITS [3:0] OF FAN-SPEED CONFIGURATION REGISTER (22h) BIT 3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 BIT 2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 BIT 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 BIT 0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 7 14 20 27 33 40 47 53 60 67 73 80 87 93 100 % DUTY CYCLE (%)
When the temperature exceeds T MIN , the fan is enabled at a minimum duty cycle programmed in bits [3:0] of the fan-speed configuration register (22h). The duty cycle increases in proportion to the temperature difference and reaches 100% at a temperature equal to (TMIN + TRANGE). A hysteresis of 5C is built into the TMIN set point to prevent the fan from starting and stopping when the temperature is at the set point. Spin-Up To ensure proper fan startup, the MAX6653/MAX6663/ MAX6664 can be set to drive the fan to 100% duty cycle for a short period on startup, and then revert to the correct duty cycle. The spin-up time is programmed by bits [2:0] in the fan characteristics register (20h). The spin-up feature can be disabled by setting bit 7 of the fan-filter register (23h) to 1; POR value is zero. Table 12 shows programming of the spin-up time.
MAX6653/MAX6663/MAX6664
Fan-Filter Mode
When the MAX6653/MAX6663/MAX6664 are used for automatic fan-speed control, the fan-filter mode helps minimize the audible effects of varying fan speeds. The fan-filter mode limits the rate at which fan speed can change. Each time a new temperature measurement is made, the fan-filter mode allows the PWM duty cycle to increment by a selectable amount. The duty cycle can change by 1/240, 2/240, 4/240, or 8/240 (0.416%, 0.833%, 1.667%, or 3.333%) of the PWM period after each temperature-monitoring cycle. This prevents sudden changes in fan speed, even when temperature changes suddenly. The filter mode is set by bit 0 of the fan-filter register (23h). To enable the fan-filter mode, write a 1 to this bit. Bits [6:5] of the same register control the size of the PWM steps. Note that the rate of change depends on both the value selected by the fan-filter bits and on the temperature
Automatic Fan-Control Mode Automatic fan-speed control is selected by setting bits [7:5] of configuration register 1 (00h) to 100 (to control speed based on the remote temperature) or 101 (to control speed based on both remote and local temperature). Program a threshold, or starting temperature TMIN, and the desired temperature range, TRANGE, into the local temp TMIN/TRANGE register (24h) for local temperature and into the remote temp TMIN/TRANGE register (25h) for remote temperature (Tables 10 and 11). If the fan control responds to both local and remote temperatures, the higher PWM duty cycle has priority.
Table 10. TRANGE Fan-Control Temperature Range Bits [2:0] TMIN/TRANGE Registers (24h and 25h)--POR = 001
BIT 2 0 0 0 0 1 BIT 1 0 0 1 1 0 BIT 0 0 1 0 1 0 TEMPERATURE RANGE (C) 5 10 20 40 80
Table 11.TMIN Fan-Control Start Temperature; Bits [7:3] TMIN/TRANGE Registers (24h--POR = 01000 and 25h--POR = 01100
BIT 7 MSB = +64C Min threshold = 0C Max threshold = +127C LSB/step size = +4C POR = +48C or 01100b BIT 6 BIT5 BIT 4 BIT3 LSB = +4C
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11
Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Table 12. Spin-Up Time; Bits [2:0] Fan Characteristics Register (20h)--POR = 101
BIT 2 0 0 0 0 1 1 1 1 BIT 1 0 0 1 1 0 0 1 1 BIT 0 0 1 0 1 0 1 0 1 SPIN-UP TIME (s) 0.2 0.4 0.6 0.8 1 2 4 8
clock frequency into a fan-speed counter. The measurement is initialized on the starting edge of a PWM output if fan-speed measurement is enabled by setting bit 2 of configuration register 2 (01h) to 1. Counting begins on the leading edge of the second tachometer pulse and lasts for two tachometer periods or until the counter overranges (255). The measurement repeats unless monitoring is disabled by resetting bit 2 in the configuration register 2 (01h). The measured result is stored in the fan-speed reading register (08h). The fan-speed count is given by: The fan-speed count is given by:000 675, Count = RPM x N where RPM = fan speed in RPM. N determines the speed range and is programmed by bits [7:6] in the fan characteristics register (20h) as shown in Table 14. When the speed falls below the value in the speed range column, a fan failure is detected. The TACH/AIN input can be either a digital signal (from the fan's tachometer output) or an analog signal, depending on the setting of bit 2 of the configuration register 1 (00h). The default setting is zero, which sets up TACH/AIN as a digital input. For the analog input (Figure 4), the detected voltage threshold is typically at 250mV, which is appropriate for sensing the voltage of a sense resistor connected to the ground lead of a 2wire fan. The AIN input only responds to pulse widths greater than 10s.
Table 13. Fan Filter Ramp Rate; Bits [6:5] Fan Filter Register (23h)--POR = 10;
BIT 6 0 0 1 1 BIT 5 0 1 0 1 RAMP RATE (x100% / 240) 1 2 4 8 RAMP RATE (% DUTY CYCLE) 0.416 0.833 1.667 3.333
measurement rate, which is controlled by bits [4:2] of the fan-filter register (23h). Table 5 shows the effect of the temperature measurement rate control bits. As an example, assume that the temperature measurement rate is 2Hz, or 0.5s per monitoring cycle, and the fan-filter rate is 0.416% per monitoring cycle. For the fan drive to change from 50% to 100% requires 50% / 0.416% = 120 temperature monitoring cycles. Thus, for a temperature-monitoring cycle of 0.5s, the time required for the drive to change from 50% to 100% is 60s.
TACH INPUT 0.1F VREF 1 100 VREF 2 CLK MAX6653 MAX6663 MAX6664
FF
Fan-Speed Measurement
The fan speed is measured by using the relatively slow tachometer signal from the fan to gate an 11.25kHz
Figure 4. Simplified Tachometer Analog Input Structure
Table 14. N Factor for Speed-Range Adjustment (Assuming Two Tachometer Pulses per Revolution)
FAN CHARACTERISTICS REGISTER (20h) POR = 01 BIT 7 0 0 1 1 BIT 6 0 1 0 1 N 1 2 4 8 SPEED RANGE (FAIL SPEED) (RPM) 2647 1324 662 331
12
______________________________________________________________________________________
Temperature Monitors and PWM Fan Controllers
Figure 5 shows a schematic using a current-sensing resistor and a coupling capacitor to derive the tachometer information from the power-supply current of a 2-wire fan. This circuit allows the speed of a 2-wire fan to be measured even though the fan has no tachometer signal output. The sensing resistor, RSENSE, converts the fan commutation pulses into a voltage and this voltage is AC-coupled into the TACH/AIN input through coupling capacitor C1. The value of RSENSE is on the order of 1 to 5, depending on the fan, and the value of the coupling capacitor C1 is 0.01F. When using this method, set bit 2 of configuration register 1 to 1.
MAX6653/MAX6663/MAX6664
5V
3.3V 100 (TYP) PWM_OUT MAX6653 MAX6663 MAX6664 TACH/AIN 2 RSENSE 2-WIRE FAN
N NDT3055L
C1
Fan-Fault Detection
The FAN_FAULT output is used to indicate fan slow down or failure. POR disables the FAN_FAULT output on the MAX6653/MAX6663. POR enables FAN_FAULT output on the MAX6664. If FAN_FAULT is not enabled, writing a logic 1 to bit 4 of configuration register 1 (00h) enables the FAN_FAULT output pin. Either underspeed or stalled fans are detected as fan faults. FAN_FAULT is asserted low only when five consecutive interrupts are generated by the MAX6653/MAX6663/ MAX6664s' INT due to fan faults. The MAX6653/ MAX6664 apply 100% duty cycle for the duration of the spin-up time once an INT is asserted. The MAX6663 goes to 100% duty cycle for the duration of the spin-up time once INT is asserted and status register 1 is read. Fan-fault detection works by comparing the value of the fan tachometer high-limit register (10h) with the value of the fan-speed reading register (08h), which contains the value of the most recent fan-speed measurement. Note that the value of the fan-speed reading register (08h) must exceed the value of the fan tachometer high limit (10h) by 1 in order to qualify as a fault. The fault generates an interrupt signal by asserting the INT output, but does not cause the FAN_FAULT output to assert until five consecutive failures have been detected. The fan runs at 100% duty cycle when five consecutive failures have been detected, whether FAN_FAULT is enabled or not. As an example of the function of the fan-fault detection, assume a fan is stalled or under speed. The MAX6663 initially indicates the failure by generating an interrupt on the INT pin. The fan fault bit (bit 1) of interrupt status register 1 (02h) is also set to 1. Once the processor has acknowledged the INT by reading status register 1, the INT is cleared. PWM_OUT is then brought high for a 2s (fan
Figure 5. Using the MAX6653/MAX6663/MAX6664 with a 2-Wire Fan
spin-up default, Table 12) spin-up period to restart the fan. Subsequent fan failures cause INT to be reasserted and PWM_OUT to be brought high (following a status register 1 read) for a spin-up period each time to restart the fan. Once the fifth tachometer failure occurs, the FAN_FAULT is asserted to indicate a critical fan failure. A MAX6653/MAX6664 example is somewhat simpler. Again assume the fan is stalled or under speed. The MAX6653/MAX6664 initially indicate the failure by generating an interrupt on the INT pin. The fan fault bit of the interrupt status register is set to 1. PWM_OUT goes high for the programmed spin-up time (2s default) to restart the fan. Each subsequent fan failure causes another spinup. Once the fifth tachometer failure occurs, the FAN_FAULT output is asserted (if enabled) and the PWM output is driven to 100%. When the FAN_FAULT output is disabled (register 00h, bit 4), spin-ups are still attempted whenever the tach count is greater than the value in the fan tachometer high-limit register (10h). If fan faults and their associated spin-ups are not desired, the fan tachometer highlimit register (10h) to FF. This prevents the tach count from ever exceeding the limit and faults are not detected. Simply disabling the tachometer input (register 01h, bit 2) leaves the fan fault function enabled and can result in fan faults.
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13
Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Alarm Speed
For the MAX6663, the alarm speed bit, bit 0 of status register 1 (02h), indicates that the PWM duty cycle is 100%, excluding the case of fan spin-up. For the MAX6653/MAX6664, this bit indicates that the THERM output is low. Once this bit is set, the only way to clear it is by reading status register 1. However, the bit does not reassert on the next monitoring cycle if the condition still exists. It does assert if the condition is discontinued and then returns. Power-On Default Conditions At power-up, the MAX6653/MAX6663/MAX6664 are monitoring temperature to protect the system against thermal damage. The PWM outputs are in known states. Note that although the "Monitoring" bit (Configuration register 1, Bit 0) is enabled, automatic fan speed control does not begin until a 1 is rewritten to Bit 0. Other default conditions as listed in the Register Summary section. After applying power to the MAX6653/MAX6663/ MAX6664, set the desired operating characteristics (fan configuration, alarm thresholds, etc.). Write to Configuration register 1 last. When a 1 is first written to Bit 0 of this register, fan control will commence as determined by the register contents. memory buses, and ISA/PCI buses. 2) Do not route the DXP-DXN lines next to the deflection coils of a CRT. Also, do not route the traces across fast digital signals, which can easily introduce 30C error, even with good filtering. 3) Route the DXP and DXN traces in parallel and in close proximity to each other, away from any higher voltage traces, such as 12VDC. Leakage currents from PC board contamination must be dealt with carefully since a 20M leakage path from DXP to ground causes about 1C error. If high-voltage traces are unavoidable, connect guard traces to GND on either side of the DXP-DXN traces (Figure 6). 4) The 10-mil widths and spacing recommended in Figure 6 are not absolutely necessary, as they offer only a minor improvement in leakage and noise over narrow traces. Use wider traces when practical. 5) Add a 200 resistor in series with VCC for best noise filtering (see Typical Operating Circuits).
GND 10 MILS 10 MILS DXP MINIMUM 10 MILS DXN 10 MILS GND
PC Board Layout
Follow these guidelines to reduce the measurement error of the temperature sensors: 1) Place the MAX6653/MAX6663/MAX6664 as close as is practical to the remote diode. In noisy environments, such as a computer motherboard, this distance can be 4in to 8in (typ). This length can be increased if the worst noise sources are avoided. Noise sources include CRTs, clock generators,
Figure 6. Recommended DXP/DXN PC Traces
Table 15. Power-On Default Conditions
MAX6653 Temperature Monitoring PWM Output PWM Mode Duty cycle setting (not enabled until a 1 is written to Bit 0 of Register 00h) PWM Polarity Monitoring at 4Hz Low PWM duty cycle control mode 33% Inverted (100% duty cycle = output high) High PWM duty cycle control mode 100% Not Inverted (100% duty cycle = output low) MAX6663 Monitoring at 4Hz High Automatic fan speed control mode Automatic Not Inverted (100% duty cycle = output low) MAX6664 Monitoring at 4Hz
14
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Temperature Monitors and PWM Fan Controllers
Register Summary
Addr(H) READ/WRITE POR STATE DESCRIPTION Configuration register 1: Bits [7:5]: Setting the fan-speed control mode: Bit 7 = 1: Enables automatic fan-speed control mode. Bits [6:5] = 00: Remote temperature controls the fan speed. Bits [6:5] =11: Both remote and local temperature control the fan speed. Bit 7 = 0, Enables PWM control mode or RPM control mode. Bits [6:5] = X0: PWM duty cycle control mode. Bits [6:5] = X1: RPM control mode. Bit 4: FAN_FAULT output enable: 1: FAN_FAULT output enabled; 0: (default) FAN_FAULT output disabled. Bit 3: Invert the PWM output: 0: (default) PWM active low; 1: (inverted) PWM active high. Bit 2: TACHOMETER digital/analog input selection: 0: (default) TACHOMETER is a logic input; 1: TACHOMETER is an analog input. Bit 1: INT output enable: 0: INT output disabled; 1: INT output enabled. Bit 0: Monitoring: 0: sleep mode; 1: (default) active temperature monitoring and fan-speed control. (Keep this bit set to 1 for MAX6663.) Although the default value of this bit is 1, fan speed control for the MAX6653 and MAX6664 is inactive until a 1 is written to this bit. Configuration register 2: Bit 7: Reset: Setting this bit to 1 restores all registers to POR default states; self-clears to zero after reset. Bit 6: Unused. Bit 5: Remote temperature enable: 0: interrupts disabled for remote channel; 1: interrupts enabled for remote channel; defaults to 1 unless a diode fault is detected on power-up. Bit 4: Local temperature enable: 0: interrupts disabled for local channel; 1: (default) interrupts enabled for local channel. Bit 3: INT input function mask: 0: enable INT input function; 1: (default) disable INT input function. Bit 2: TACHOMETER input enable: 0: disable TACHOMETER input; 1: (default) enable the TACHOMETER input. (Keep this bit set to 1 for MAX6663.) Bit 1: SMBus timeout enable: 0: SMBus timeout disabled; 1: (default) SMBus timeout enabled. Bit 0: PWM out enable: 0: PWM output disabled; 1: (default) PWM output enabled.
MAX6653/MAX6663/MAX6664
MAX6653 0000 1001 00 R/W MAX6663 00000001 MAX6664 10010001
01
R/W
0111 1111
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15
Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Register Summary (continued)
Addr(H) READ/WRITE POR STATE DESCRIPTION Status register 1: Bit 7: Local temp low: 1: Local temp low interrupt limit has been exceeded. This bit is cleared by reading status register 1 for the MAX6653/MAX6663/MAX6664 or completing an alert response protocol for the MAX6664. This bit is asserted on the next cycle if the local temperature is still less than the limit. Bit 6: Local temp high: 1: Local temp high interrupt limit has been exceeded. This bit is cleared by reading status register 1 for the MAX6653/MAX6663/MAX6664 or completing an alert response protocol for the MAX6664. This bit is asserted on the next cycle if the local temperature is still greater than the limit. Bit 5: Remote-diode error: 1: remote-diode short circuit or open circuit detected. Bit 4: Remote temp THERM: 1: Remote temp THERM limit has been exceeded. This bit is cleared by reading status register 1. Bit 3: Remote temp low: 1: Remote temp low interrupt limit has been exceeded. This bit is cleared by reading status register 1 for the MAX6653/MAX6663/MAX6664 or completing an alert response protocol for the MAX6664. This bit is asserted on the next cycle if the remote temperature is still less than the limit. Bit 2: Remote temp high: 1: Remote temp high interrupt limit has been exceeded. This bit is cleared by reading status register 1 for the MAX6653/MAX6663/ MAX6664 or completing an alert response protocol for the MAX6664. This bit is asserted on the next cycle if the remote temperature is still greater than the limit. Bit 1: Fan fault: 1: The fan is running under speed. This bit is cleared by reading status register 1 or completing an alert response protocol. This bit is asserted again on the next cycle if the fan fault still exists. Bit 0: Alarm speed: For MAX6663, this bit is set to 1 when the PWM duty cycle = 100%. Once read, this bit does not reassert on the next monitoring cycle, even if the condition still exists. It is asserted again if the condition is discontinued and then returns. For the MAX6653/MAX6664, this bit is set to 1 when the THERM output goes to low. Status register 2: Bit 7: THERM: 1: THERM has been pulled low externally. This bit clears on a read of status register 2. Bit 6: Local temp THERM: 1: Local temp THERM limit has been exceeded. This bit is cleared by reading status register 2. Bits [5:0]: Unused. Extended bits of temperature data: Bits [7:5]: Extended bits for local temperature data. Bits [4:3]: Unused. Bits [2:0]: Extended bits for remote temperature data. Fan-speed reading register: This register contains the fan-speed tachometer measurement.
02
R
0000 0000
03
R
0000 0000
06
R
0000 0000
08
R
1111 1111
16
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Temperature Monitors and PWM Fan Controllers
Register Summary (continued)
Addr(H) 0A 0B READ/WRITE POR STATE R R 0001 1110 (30C) 0001 1110 (30C) DESCRIPTION Local temperature data: This register contains the 8 MSBs of the local temperature measurement. Remote temperature data: This register contains the 8 MSBs of the local temperature measurement. Local temperature offset: Bit 7: Sign bit; when zero, the offset value in bits [3:0] is added to the measured local temperature reading. When this bit is 1, the offset value in bits [3:0] is subtracted from the local temperature reading. Bits [6:4] Unused. This bits normally reads back zeros. Bits [3:0] Offset value. This is added to or subtracted from the measured local temperature reading. Remote temperature offset: Bit 7: Sign bit: When 0, the offset value in bits [3:0] is added to the measured remote temperature reading. When this bit is 1, the offset value in bits [3:0] is subtracted from the remote temperature reading. Bits [6:4] Unused: These bits normally read back zeros. Bits [3:0] Offset value: This is added to or subtracted from the measured remote temperature reading. Fan tachometer high-limit register: Contains the limit of the fan-speed measurement. It detects a stalled fan if the measured fan-speed data (reg_08h; proportional to fan period) is larger than the limit. Local temp high limit: Contains the local high-temperature interrupt limit. Local temp low limit: Contains the local low-temperature interrupt limit. Local temp THERM limit: Contains the local high-temperature limit for the THERM output. Default is +70C for the MAX6663/MAX6664; CRIT0 and CRIT1 determine the default value for the MAX6653 (see Table 1). Remote temp high limit: Contains the remote high-temperature interrupt limit. Remote temp low limit: Contains the remote low-temperature interrupt limit. Remote temp THERM limit: Contains the remote high-temperature limit for the THERM output. Default is +100C for the MAX6663/MAX6664; CRIT0 and CRIT1 determine the default value for the MAX6653 (see Table 1). Local temp shutdown limit: Contains the local high-temperature limit for the SDL output. CRIT0 and CRIT1 determine the default value for the MAX6653 (see Table 1). Remote temp shutdown limit: Contains the remote high-temperature limit for the SDR output. CRIT0 and CRIT1 determine the default value for the MAX6653 (see Table 1).
MAX6653/MAX6663/MAX6664
0D
R/W
0000 0000
0E
R/W
0000 0000
10
R/W
1111 1111 0011 1100 (60C) 0000 0000 (0C) 0100 0110 (70C) 0101 0000 (80C) 0000 0000 (0C) 0110 0100 (100C)
14 15
R/W R/W
16
R/W
18 19
R/W R/W
1A
R/W
1B
R/W
0101 1111 (95C)
1C
R/W
0111 1101 (125C)
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17
Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Register Summary (continued)
Addr(H) READ/WRITE POR STATE DESCRIPTION Fan characteristics register: Bits [7:6]: N factor: These bits contain the N factor for the fan-speed range: 00 = 1 (fail speed =2647RPM) 01 = 2 (fail speed =1324RPM) (default) 10 = 4 (fail speed = 662RPM) 11 = 8 (fail speed = 331RPM) Bits [5:3]: PWM frequency: These bits contain the nominal PWM output frequency: 000 = 11.7Hz 001 = 15.6Hz 010 = 23.4Hz 011 = 31.25Hz (default) 100 = 37.5Hz 101 = 46.9Hz 110 = 62.5Hz 111 = 93.5Hz Bits [2:0]: Spin-up: These bits contain the fan spin-up time: 000 = 200ms 001 = 400ms 010 = 600ms 011 = 800ms 100 = 1s 101 = 2s (default) 110 = 4s 111 = 8s Fan-speed configuration register: Bits [7:4]: Unused. Bits [3:0]: PWM duty cycle: These bits contain the PWM duty cycle for the PWM duty cycle fan-control mode. They also contain the minimum duty cycle that is applied to the fan: 0000 = 0% output 0001 = 7% output 0010 = 14% output 0011 = 20% output 0100 = 27% output 0101 = 33% output (default) 0110 = 40% output 0111 = 47% output 1000 = 53% output 1001 = 60% output 1010 = 67% output 1011 = 73% output 1100 = 80% output 1101 = 87% output 1110 = 93% output 1111 =100% output
20
R/W
0101 1101
MAX6653/ MAX6664 22 R/W 01010101
MAX6663 01011111
18
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Temperature Monitors and PWM Fan Controllers
Register Summary (continued)
Addr(H) READ/WRITE POR STATE DESCRIPTION Fan filter register: Bit 7: Fan spin-up disable: 0: Spin-up enabled; 1: spin-up disabled. Bits [6:5]: Fan ramp rate: These bits set the amount the PWM duty cycle can change on each monitoring cycle: 00 = 1 (0.416%) 01 = 2 (0.833%) 10 = 4 (1.667%) (default) 11 = 8 (3.333%) Bits [4:2]: Temperature measurement rate (see Table 5). Bit 1: Unused. Bit 0: Fan filter enable. Setting the bit to 1 enables the fan filter function. Local temp TMIN/ TRANGE register: Bits [7:3]: Local TMIN: Contains the temp threshold for the automatic fan-speed control mode. When the local temperature exceeds this value, the PWM output becomes active: 00000 = 00C 00001 = +40C | 01000 = +320C (default) | 11110 = +1200C 11111 = +1240C Bits [2:0]: Local TRANGE: Contains the local temperature range for automatic fanspeed control mode. When the temperature reaches TMIN + TRANGE, the PWM duty cycle reaches 100%: 000 = +50C 001 = +100C (default) 010 = +200C 011 = +400C 100 = +800C Remote temp TMIN/TRANGE register: Bits [7:3]: Remote TMIN. Contains the temp threshold for the automatic fan-speed control mode. When the remote temperature exceeds this value, the PWM output becomes active.: 00000 = 00C 00001 = +40C | 01100 = +480C (default) | 11110 = +1200C 1111 = +1240C Bits [2:0]: Remote TRANGE: Contains the remote temperature range for automatic fanspeed control mode. When the temperature reaches TMIN + TRANGE, the PWM duty cycle reaches 100%: 000 = +50C 001 = +100C (default) 010 = +200C 011 = +400C 100 = +800C
MAX6653/MAX6663/MAX6664
23
R/W
0101 1101
24
R/W
0100 0001
25
R/W
0110 0001
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19
Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Register Summary (continued)
Addr(H) 3D 3E READ/WRITE POR STATE R R 0011 1000 0100 1101 Device ID Manufacturer ID THERM behavior/revision: Bit [7]: THERM behavior: 1: enable THERM as an output. 0: disable THERM as an output. Bits [3:0] revision number. *For MAX6663 bit 7 has to be 1 all the time. DESCRIPTION
3F
R/W
1000 0000
Twisted-Pair and Shielded Cables
Use a twisted-pair cable to connect the remote sensor for remote-sensor distances longer than 8in, or in very noisy environments. Twisted-pair cable lengths can be between 6ft and 12ft before noise introduces excessive errors. For longer distances, the best solution is a shielded twisted pair like that used for audio microphones. For example, Belden 8451 works well for distances up to 100ft in a noisy environment. At the device, connect the twisted pair to DXP and DXN and the shield to GND. Leave the shield unconnected at the remote sensor. For very long cable runs, the cable's parasitic capacitance often provides noise filtering, so the 2200pF capacitor can often be removed or reduced in value. Cable resistance also affects remote-sensor accuracy. For every 1 of series resistance, the error is approximately 0.5C.
Table 16. Remote-Sensor Transistor Manufacturers
MANUFACTURER Central Semiconductor (USA) Rohm Semiconductor (USA) Samsung (Korea) Siemens (Germany) Zetex (England) MODEL NO. CMPT3904 SST3904 KST3904-TF SMBT3904 FMMT3904CT-ND
Note: Discrete transistors must be diode connected (base shorted to collector).
Remote Diode Considerations
The accuracy of the remote temperature measurements depends on the ideality factor (n) of the remote "diode" (actually a transistor). The MAX6653/MAX6663/ MAX6664 are optimized for n = 1.008, which is the typical value for the Intel Pentium III. A thermal diode on the substrate of an IC is normally a PNP with its collector grounded. DXP should be connected to the anode (emitter) and DXN should be connected to the cathode (base) of this PNP. When the remote-sensing diode is a discrete transistor, its collector and base should be connected together. Table 16 lists examples of discrete transistors that are appropriate for use with the MAX6653/MAX6663/ MAX6664. The transistor must be a small-signal type with a relatively high forward voltage; otherwise, the A/D input voltage range can be violated. The forward voltage at
PC Board Layout Checklist
* * * * * * * Place the MAX6653/MAX6663/MAX6664 close to the remote-sense junction. Keep traces away from high voltages (+12V bus). Keep traces away from fast data buses and CRTs. Use recommended trace widths and spacings. Place a ground plane under the traces. Use guard traces flanking DXP and DXN and connecting to GND. Place the noise filter and the 0.1F VCC bypass capacitors close to the MAX6653/MAX6663/ MAX6664.
20
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Temperature Monitors and PWM Fan Controllers
the highest expected temperature must be greater than 0.25V at 10A, and at the lowest expected temperature, the forward voltage must be less than 0.95V at 100A. Large power transistors must not be used. Also, ensure that the base resistance is less than 100. Tight specifications for forward current gain (50 < <150, for example) indicate that the manufacturer has good process controls and that the devices have consistent VBE characteristics. Manufacturers of discrete transistors do not normally specify or guarantee ideality factor. This is normally not a problem since good-quality discrete transistors tend to have ideality factors that fall within a relatively narrow range. We have observed variations in remote temperature readings of less than 2C with a variety of discrete transistors. Still, it is sound design practice to verify good consistency of temperature readings with several discrete transistors from any manufacturer under consideration.
MAX6653/MAX6663/MAX6664
Typical Operating Circuits
+3.3V +5V 3-WIRE FAN +3.3V +3.3V
10k
+3.3V
2.2k
2.2k
10k 1 NDT3055L 2 TACH/AIN SMBDATA 15 10k 3 +3.3V 4 5 +3.3V 6 10k THERM SIGNAL TO THROTTLE CPU CLOCK 7 +3.3V 2.2nF 10k FAN _FAULT TO SIGNAL FAN-FAILURE CONDITION 8 FAN_FAULT DXN 9 THERM DXP 10 CPU VCC SDL 11 CRIT0 INT 14 +3.3V CRIT1 GND 13 10k SDR 12 PWM_OUT SMBCLK 16 +3.3V
CLOCK DATA
INTERRUPT TO C
MAX6653
ADD
SYSTEM SHUTDOWN
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21
Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Typical Operating Circuits (continued)
+3.3V +5V 3-WIRE FAN +3.3V +3.3V
10k
+3.3V
2.2k
2.2k
10k 1 NDT3055L 2 TACH/AIN SMBDATA 15 10k 3 N.C. INT 14 +3.3V 4 +3.3V +3.3V 6 10k THERM SIGNAL TO THROTTLE CPU CLOCK 7 +3.3V 2.2nF 10k FAN _FAULT TO SIGNAL FAN-FAILURE CONDITION 8 FAN_FAULT DXN 9 THERM DXP 10 CPU VCC N.C. 11 5 N.C. GND 13 PWM_OUT SMBCLK 16 +3.3V
CLOCK DATA
INTERRUPT TO C
MAX6663 MAX6664
ADD
N.C.
12
22
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Temperature Monitors and PWM Fan Controllers
Functional Diagram
VCC
MAX6653/MAX6663/MAX6664
ADD
SLAVE ADDRESS DECODER
SMBus INTERFACE
SMBCLK SMBDATA
TACH/AIN
TACH SIGNAL CONDITIONING
TACHOMETER
DXP DXN
REGISTER BANK ANALOG MUX ADC TEMPERATURE MEASUREMENT
INTERNAL TEMPERATURE SENSOR
BANDGAP REFRENCE
MUX
SHUTDOWN AND THERM LIMIT DECODER
(CRIT1) (CRIT0)
PWM_OUT
PWM OUTPUT CONTROLLER ALU
INT THERM FAN_FAULT (SDL) (SDR)
( ) ARE FOR MAX6653 ONLY
GND
Pin Configurations (continued)
TOP VIEW
PWM_OUT 1 TACH/AIN 2 N.C. 3 N.C. 4 GND 5 VCC 6 THERM 7 FAN_FAULT 8 16 SMBCLK 15 SMBDATA 14 INT
Chip Information
TRANSISTOR COUNT: 27,074 PROCESS: BiCMOS
MAX6663 MAX6664
13 ADD 12 N.C. 11 N.C. 10 DXP 9 DXN
QSOP
______________________________________________________________________________________
23
Temperature Monitors and PWM Fan Controllers MAX6653/MAX6663/MAX6664
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH
21-0055
E
1 1
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
QSOP.EPS

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