ADT7473 Analog Devices, Inc., ADT7473 Datasheet
ADT7473
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ADT7473 Summary of contents
Page 1
... PWM fan controller for noise sensitive or power sensitive applications requiring active system cooling. The ADT7473 can drive a fan using either a low or high frequency drive signal, monitor the temperature two remote sensor diodes plus its own internal temperature, and measure and control the speed four fans so they operate at the lowest possible speed for minimum acoustic noise ...
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... Maximum Ratings............................................................ 6 Thermal Resistance ...................................................................... 6 ESD Caution.................................................................................. Configuration and Function Descriptions............................. 7 Ty pical Performance Characteristics ............................................. 8 Product Description....................................................................... 10 Comparison Between ADT7467 and ADT7473 .................... 10 How to Set the Functionality of Pin 9...................................... 10 Recommended Implementation............................................... 10 Serial Bus Interface..................................................................... 11 Write Operations ........................................................................ 12 Read Operations ......................................................................... 13 SMBus Timeout .......................................................................... 13 Voltage Measurement I nput ...
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... Between the ADT7467 and ADT7476 sec tion .....................................................................10 anges to SMBAL ERT Ch Interrupt Behavior Section Changes to Interrupt Mask Register 1 (0x74) Section ...............22 Changes to Fan Drive Using PWM Control................................26 Changes to Reading Fan Speed from the ADT7473...................28 C hange rderin 6/05—Revisi ................. 21 Rev Page ...
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... ADT7473 SPECIFICATIONS unless other A MIN MAX CC MIN MAX Table 1. Pa rameter POWER SUPPLY Supply Voltage Supply Current MP-TO-DIGITAL CONV ERTER Local Sensor Accuracy Resolution Remote Diode Sensor Accuracy Resolution Remote Sensor Source Current AN ALOG-TO-DIGITAL CONVERTER ...
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... V V Maximum input voltage V V Minimum input voltage V p µ µ See Figur µs µs µs ns µ Can be optionally disabled = 0.8 V for a falling edge and HD; STA t t SU; STA SU; STO S ADT7473 = 2.0 V for ...
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... ADT7473 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Positive Supply Voltage ( Voltage on Any Input or Output Pin Input Current at Any Pin Package Input Current Maximum Junction Temperature (T max) J Storage Temperature Range Lead Temperature, Soldering IR Reflow Peak Temperature Lead Temperature (Soldering, 10 sec) ESD Rating ...
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... Bidirectional THERM pin. Can be used to time and monitor assertions on the THERM input as well as to assert when an ADT7473 THERM overtemperature limit is exceeded. For example, the pin can be connected to the PROCHOT output of an Intel Pentium 4 processor or to the output of a trip point temperature sensor. Can be used as an output to signal overtemperature conditions ...
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... ADT7473 TYPICAL PERFORMANCE CHARACTERISTICS GND –20 –40 – LEAKAGE RESISTANCE (MΩ) Figure 4. Remote Tempera re Error vs. PCB Resistance tu 0 –10 –20 –30 –40 –50 – CAPACITANCE (nF) Figure 5. Temperature Error vs. Capacitance Between D+ and D− ...
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... OIL BATH TE MPERATURE (°C) Figure 11. Internal Temperature Error vs. Temperature 3.0 2.5 2.0 1.5 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 500M 600M 85 105 125 Rev Page ADT7473 –40 – 105 OIL BA TH TEMPERATURE (°C) Figure 12. Remote Temperature Error vs. Tempe 125 rature ...
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... The following list shows some comparisons between the ADT7467 and the ADT7473: • The ADT7473 can be powered via a 3.3 V supply only, and does not support 5 V operation, while the AD Violating this specification results in irreversible damage to the ADT7473. See the ADT7473 Specifications sectio for more information. • ...
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... SERIAL BUS INTERFACE On PCs and servers, control of the ADT7473 is carri using the SMBus. The ADT7473 is connected to this bus as a slave device, under the control of a master controller, which is usually (but not necessarily) the ICH. The ADT7473 has a fixed 7 -bit serial bus address of 0101110 or 0x2E ...
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... In addition to supporting t he send byte and receive byte protocols, the ADT7473 also supports the read byte protocol. (See System Management Bus Specifications Rev. 2 for more information; this document is available from In l.) If several read or write operations must be performed in succes- ...
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... SMBALERT is cleared only if the error condition is gone. SMBus TIMEOUT eading a single The ADT7473 includes an SMBus timeout feature. If there is n viously set up. SMBus activity for 35 ms, the ADT7473 ass single byte from a locked and releases the bus. This prev locking or holding the SMBus expecting data ...
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... ADC without the a Single-Chann S etting Bit 6 of Configuration R ADT7473 in d output m ode, the ADT7473 can hannel only. If the internal AD nd converts a vol tage read every 711 µs. The ns to reduce noise ...
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... The t echnique used in the ADT7473 when the device is operated at three different currents. BE Previous devices have used only two operating currents, but the use of a third current allows automatic cancellation of resis- tances in series with the external temperature sensor ...
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... Bold numbers denote 2 LSBs of measurement in Extended Resolution Register 2 (0x77) with 0.25°C resolution. Remote Temperature Measurement The ADT7473 can measure the temperature of two remote diode sensors or diode-connected transistors connected to Pin 10 and Pin 11, or Pin 12 and Pin 13. The forward voltage of a diode or diode-connected transistor ...
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... This filtering reduces both common-mod differential noise. SERIES RESISTANCE CANCELLATION Parasitic resistance to the ADT7473 D+ and D− inputs (seen in series with the remote diode) is caused by a variety of factors including PCB track resistance and track length. This series resistance appears as a temperature offset in the remote sensor’s temperature measurement. This error typically causes a 0.5° ...
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... Reading Temperature from the ADT7473 It is important to note that the temperature can be read from the ADT7473 as an 8-bit value (with 1°C resolution 10-bit value (with 0.25°C resolution). If only 1°C resolution is required, the temperature readings can be read back at any time and in no particular order ...
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... Single-Channel ADC Conversions Setting Bit 6 of Configuration Register 2 (0x73) places the ADT7473 into single-channel ADC conversion mode. In mode, the ADT7473 can be made to read a single tempera channel only. The appropriate ADC channel is selected by writing to Bits [7:5] of the TACH1 minimum high byte register (0x55). ...
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... Rev Page Low Byte = 0xFF default inimum High Byte = 0xFF default ave been programmed, the ADT7473 can be toring. The ADT7473 measures all voltage and d-robin format and sets the owers up with this bit set. The ADC measures put in turn and, as each measuremen ...
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... The total monitoring cycle time for averaged voltage and temperature monitoring is 146 ms. The total monitoring cycle time for voltage and temperature monitoring with averaging disa led is 19 ms. The ADT7473 is a deriva esu lt, the total conversion time in th ...
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... Once Pin 9 is configured as THERM , it must be enabled by setting Bit 1 of Configuration Register 3 (0x78). THERM as an Input When THERM is configured as an input, the ADT7473 can time assertions on the THERM pin. This can be useful for connecting to the PROCHOT output of a CPU to gauge system performance ...
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... The user can also set up the ADT7473 so that, when the THERM pin is driven low externally, the fans run at 100%. The fans run at 100% for the duration of the time the THERM pin is pulled low. This is done by setting the BOOST bit (Bit 2) in Configuration Register 3 (0x78 ...
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... THERM bidirectional. This means that if th appropriate temperature channel exceeds the temperature limit, the THERM output asserts. If the ADT7473 is not pulling THERM low, but THERM is pulled low by an external device (such as a CPU overtemperature signal), the THERM timer also times THERM assertions ...
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... Figure 30. Functional Block Diag Configuring the THERM Pin as Bidirectional In addition to monitoring THERM as an input, the ADT7473 can optionally drive THERM low as an output. When PROCHOT is bidirectional, THERM can be used to throttle th processor by asserting PROCHOT . The user can preprogram system-critical thermal limits. If the temperature exceeds a thermal limit by 0.25° ...
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... For 4-wire fans, the PWM drive might need only a pull-up resistor. In many cases, the 4-wire fan PWM input has a built-in pull-up resistor. The ADT7473 PWM frequency can be set to a selection of low fre quencies or a single high PWM frequency. The low frequency options ar e usually used for 3-wir high frequency option is usually used with 4-wire fans ...
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... Pin 4, Pin 6, Pin 7, and Pin 9 (when configured as TACH inputs) are open-drain TACH inputs intended for fan speed measurement. Signal conditioning in the ADT7473 accommodates the slow rise and fall times typical of fan tachometer outputs. The maximum input signal range 3 ...
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... TACH limit by 1 sets the appropriate status bit and can counted. used to generate an SMBALERT . Measuring Fan TACH When the ADT7473 starts up, TACH measurements are locked. In effect, an internal read of the low byte has been ma each TACH input. The net result of th read ...
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... Fan Spin-Up WM channel but associated dc bit in The ADT7473 has a unique fan spin-up function. It spins allows TACH the fan at 100% PWM duty cycle until two TACH pulses are or fans connected detected on the TACH input. Once two TACH pulses are ...
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... Programming the Automatic Fan Speed MIN Co trol Loop section manual fan speed control mode, the ADT7473 allows the duty cycle of any PWM output to be manually adjusted. Thi can be useful if the user wants to change fan speed in softwa or adjust th e PWM duty cycle output for test purposes ...
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... XNOR TREE TEST MODE The ADT7473 includes an XNOR tree test mode. This mode is useful for in-circuit test equipment at board-level testing. By applying stimulus to the pins included in the XNOR tree possible to detect opens or shorts on the system board. ...
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... ADT7473 If V goes high (the system processor power rail is powered CC up), a fail-safe timer begins to count down. If the ADT7473 is not addressed by any valid SMBus transactions before the fail- safe timeout (4.6 seconds) lapses, the ADT7473 drives the fans to full speed. If the ADT7473 is addressed transaction after this point, the fans stop, and the ADT7473 assumes its default settings and begins normal operation ...
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... PWM outputs. The three PWM outputs c used to control up to four fans. The ADT7473 allows the speed of four fans to be monitored. Each temperature channel has a thermal calibration block, allowing the designer to individually configure the thermal characteristics of each temperature channel ...
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... This influences the choice of whether to us TACH4 pin or to reconfigure it for the THERM function the CPU fan to be controlled using the ADT7473 or will it run at full speed 100% of the time? If run at full speed, 100% of the time, this frees up a PWM output, but the system is louder ...
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... Recommended Implementation 1 Configuring the ADT7473 Figure 46, provides the system designer with the following features: • Two PWM outputs for fan control three fans. ( front and rear chassis fans are connected in parallel. • Three TACH fan speed measurement inputs. • ...
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... ADT7473 STEP 2: CONFIGURING TH E MUX After the system hardware configuration is determined, the f can be assigned to particular temperature channels. Not only can fans be assigned to individual channels, but the behavio the fans is also configurable. For example, fans can be run under automatic fan control, manually (under software control the fastest speed calculated by multiple tem erature channels ...
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... Mux Configuration Example This is an example of how to conf igure the mux in a system using the ADT7473 to control three fans. The CPU fan sink is controlled by PWM1, the front chassis fan is controlled by PWM2, and the rear chassis fan is controlled by PWM3. The mux is configured for the following fan control behaviors: • ...
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... ADT7473 STEP 3: T SETTINGS FOR THERMAL MIN CALIBRATION CHANNELS T is the temperature at which the fans start to turn on und MIN automatic fan control. The speed at which the fan runs at T programmed later. The T values chosen are temperature MIN channel specific, for example, 25°C for ambient channel, 30°C for VRM temperature, and 40° ...
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... ADT7473 100 MIN THERMAL CALIBRATION T MIN THERMAL CALIBRATION REMOTE 2 = CPU TEMP T MIN LOCAL = THERMAL CALIBRATION VRM TEMP T MIN REMOTE 1 = AMBIENT TEMP PWM 100% MIN RAMP CONTROL (ACOUSTIC ENHANCEMENT TACHOMETER 1 RAN GE MEASUREMENT PWM MIN 100% RAMP CONTRO MUX (ACOU ENHANCEMENT) ...
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... ADT7473 STEP 4: PWM FOR EACH PWM (FAN) OUTPUT MIN PWM is the minimum PWM duty cycle at which each fan MIN the system runs also the start speed for each fan under automatic fan control once the temperature rises above T (see Figure 50). For maximum system acoustic benefit, PWM should be set as low a s possible ...
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... PWM duty cycle). 3. Determine the slope of the required control loop to meet these requirements. 4. Gra phically ADT7473 evaluation software. Ask your local Analog Devices representative for details. Figure 54 shows how adjusting PWM 100% Rev Page FOR TEMPERATURE CHANNELS RANGE temperature is ...
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... ADT7473 T is implemented slope, which means that as PWM RANGE is changed, T changes, but the actual slope remains the RANGE same. The higher the PWM value, the smaller the effective MIN T , that is, the fan rea ches full speed (100 lower RANGE temperature ...
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... T RANGE T RANGE This example uses the mux configuration described in the Step 2: Configuring the Mux section, with the ADT7473 connected as shown in Figure 58. Both CPU temperature and VRM temperature drive the CPU fan connected to PWM1. Ambient temperature drives the fro P WM2 and PWM3. The front chassis fan is configured to run ...
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... ADT7473 Note on 4-Wire Fans The control range for 4-wire fans is much wider than that of 3 -wire fans. In many cases, 4-wire fans can start with a PWM drive of as little as 20%. 100 TEMPERATURE ABOVE T 100 ...
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... CONTROL PWM PWM1 GENERATOR TACH1 PWM CPU F CONFIG RAMP CONTROL PWM PWM2 GENERATOR TACH2 PWM CO NFIG FRONT CHASSIS RAMP CONTROL PWM PWM3 GENERATOR TACH3 AND 4 REAR CHASSIS . Bits [7:5] of the Enhance MIN . If the fans are always on, the T MIN . MIN ADT7473 AN SINK HYST ...
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... ADT7473 100 MIN THERMAL CALIBRATION T MIN THERMAL CALIBRATION REMOTE 2 = CPU TEMP T MIN LOCAL = THERMAL CALIBRATION VRM TEMP T MIN REMOTE 1 = AMBIENT TEMP Figure 60. The T Enhance Acoustics Register 1 (0x62) Bit 7 (MIN3 PWM3 is off (0% PWM duty cycle) w temperature is below T − MIN HYST Bit 7 (MIN3 PWM3 runs at PWM3 minimum duty cy below T − ...
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... DYNAMIC T CONTROL MODE MIN In addition automatic fan speed control mode described in the Automatic Fan Control Overview section, the ADT7473 has a mode that extends the basic automatic fan speed contr loop. Dynamic T control allows the ADT7473 to intelligentl MIN adapt the system’s cooling solution for best system performance or lowest possible system acoustics, depending on user or design requirements ...
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... MIN performance and measured temperature. This is important because instead of designing for the worst case, the system thermals can be defined as operating zones. The ADT7473 can self-adjust its fan control loop to maintain either an operating zone temperature or a system target temperature. For example, it can be specified that the ambient temperature in a system should be maintained at 50° ...
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... The hotter each zone is allowed to be, the quieter the system, because the fans are not required to run as fast. The ADT7473 in eases or decreas speeds as necessary to maintain the operating point temp tur , allowing for system-to-system variation and removing the ...
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... A number of conditions govern the situations in which T can increase or decrease. MIN Short Cycle and Long Cycle The ADT7473 implements t cycle. The short cycle takes place every n monitoring cycles. value MIN The long cycle takes place every 2n monitoring cycles. The value programmable for each temperature channel. The ...
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... The temperature is above T . The dynamic T MIN is turned off below T . MIN ADT7473 emperature minus s MIN en is reduced by MIN d, e oring cycle, then ...
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... PROCHOT output pulls the THERM control is MIN input low on the ADT7473. This gives the maximum temperature at which the Pentium 4 can run before clock modulation occurs. Rev Page CHANGE IN T ...
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... PWM duty cycle responds immediately to temperature change. Any impulses in temperature can cause an impulse in fan noise. For psycho- acoustic reasons, the ADT7473 can prevent the PWM output from reacting instantaneously to temperature changes. Enhanced acoustic mode controls the maximum change in PWM duty cycle at a given time ...
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... CPU cooling fan, even though both fans are controlled by Remote 1 temperature. The fan-centric approach is how acoustic enhancement works on the ADT7473. Enabling Acoustic Enhancement for Each PWM Output Enhance Acoustics Register 1 (0x62) Bit enables acoustic enhancement on PWM1 output ...
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... PWM output to ramp up from 0% to 100% duty cycle for an instantaneous change in temperature. This can be tested by putting the ADT7473 into manual mode and changing the PWM output from 0% to 100% PWM duty cycle. The PWM output takes 35 seconds to reach 100% when a ramp rate of 1 time slot is selected. ...
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... ADT7473 Figure 74 shows remote temper ature plotted against PWM duty c ycle for enhanced acoustics m ode. The ramp rate is set to 48, which corresponds to the fastest ra mp rate. Assume that a new temperat e read g is available ur in every 115 m it takes approximately 0.76 seconds to go from 33% duty cycle to ...
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... Figure 78 . How Fa n Reacts to T empera in Enhanced A coust ics Mo Slower Ramp Ra tes The ADT7473 programm ed for much longer ramp times by slo wing rates. Each ram p rate factor of 4. PWM1 Configu ation Register (0x5C) r Bit [3] SLOW ows the ramp rate for PWM1 by 4 ...
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... ADT7473 REGISTER TABLES Table 17 Registers 74 Addre ss R/W Description Bit 7 0x21 R V Readin g 9 CCP 0x22 R V Reading 9 CC 0x25 R Remote 1 9 Temperatu re 0x26 R Local 9 Temperature 0x27 R Remote 2 9 Temperature 0x28 R TACH1 Low Byte 7 0x29 R TACH1 High Byte 15 0x2A R TACH2 Low Byte ...
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... ACOU2 EN3 Rev Page ADT7473 Bit 2 Bit 1 Bit 0 Default 0x01 0xFF 0x01 0xFF 0xFF 0xFF 0xFF ...
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... MSB reading registers are frozen until read. Both the extended resolution registers and the MSB registers are frozen (Bit 1 of the Dynamic T Control Register 1, 0x36) is set, V CCP MIN 3 V (Pin 3) is the supply voltage for the ADT7473. CC Bit 6 Bit 5 Bit 4 Bit ...
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... ADT7473 reports the PWM duty cycles tic fan speed control mo de. During fan start up, these registers by writing to these register s. control feature is enabled. MIN ADT7473 ...
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... ADT7473 Table 23. Register 0x36—Dynamic T MIN Bit N ame R/W Descrip tion [0] C YR2 R /W MSB of 3-bit remote 2 cycle value. The other two bits of the code reside in Dynamic T (Reg. 0x 37). These three bits define the delay time between making subsequent T in terms of the number of monitoring cycles. The system has associated thermal time constants that need to be ...
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... ADT7473 adjustments in MIN ycles. The and the gister 1 ents i n the control ermal time ...
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... Power-o n default = 0. This bit is not locked at any time. this bit when the ADT7473 is configured to measure current from an ADI ADOPT measure the C PU’s core voltage. This bit allows monitoring software to display CPU watts ckable bit.) an spin-up for t wo TACH pulses ...
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... TACH3 minimum low byte. TACH3 minimum high byte. TACH4 minimum low byte. TACH4 minimum high byte. R/W 1 Description R/W PWM1 configuration. R/W PWM2 configuration. R/W PWM3 configuration. Rev Page ADT7473 Power-On Default 0x00 0xFF 0x00 0xFF Power-On Default 0x01 0xFF 0x01 0xFF 0x01 0xFF Power-On Default ...
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... ADT7473 Table 34. Register 0x5C, Register 0x5D, and Register 0x5E—Configuration Register Bit R/W [2: R/W [3] SLOW R/W [4] INV R/W [7:5] BHVR R/W Table 35. TEM P T /PWM Frequency Registers RANGE 1 R egister Address R/W 0x5F R/W 0x60 R/W 0x61 R/W 1 These registers become read-only when the Configuration Register 1 lock bit is set. Any further attempts to write to these registers have no effect. ...
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... Freq RANGE bles high frequen cy PWM output for 4-wire fans. Once enabled, 3-wire fan-specific settings have 1 enables high fre quency mode for Fan 1. equency mode for Fan 2. Rev Page ADT7473 uency Registers (Power-On Default = 0xCC) ...
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... SYNC = 0 synchronizes only TACH3 and TACH4 to PWM3 output. [5] MIN R/W When the ADT7473 is in automatic fan control mode, this bit defines whether PWM1 is off (0% duty cycle PWM1 minimum duty cycle when the controlling temperature is below its duty cycle below PWM1 minimum duty cycle below T ...
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... Remote 1 temperature T . MIN Local temperature T . MIN Remote 2 temperature T . MIN , the appropriate fan runs at minimum speed and increases MIN Rev Page ADT7473 Power-On Default 0x80 (50% duty cycle) 0x80 (50% duty cycle) 0x80 (50% duty cycle) Power-On Default 0x9A (90°C) 0x9A (90°C) 0x9A (90°C) ...
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... ADT7473 1 Table 42. THERM Limit Registers 2 Register Address R/W 0x6A R/W 0x6B R/W 0x6C R/W If any temperature measured exceeds its THERM limit, all PWM outputs drive their fans at 100% duty cycle. This is a fail-safe mechanism incorporated to cool the 1 system in the event of a critical over temperature. It also ensures some level of cooling in the event that software or hardware locks up. If set to 0x80, this feature is disabled. The PWM output remains at 100% until the temperature drops below THERM Limit − ...
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... ATTN = 1, the ADT7473 removes the attenuators from the V input can be used for other functions such as connecting up external sensors. CONV = 1, the ADT7473 is put into a single-channel ADC conversion mode. In this mode, the ADT7473 can be made to read continuously from one input only, for example, Remote 1 temperature. The appropriate ADC channel is selected by writing to Bits [7:5] of TACH1 minimum high byte register (0x55) ...
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... ADT7473 Table 50. Register 0x75—Interrupt Mask Register 2 (Power-On Default <7:0> = 0x00) Bit Name R/W [1] OVT Read only [2] FAN1 R/W [3] FAN2 R/W [4] FAN3 R/W [5] F4P R/W [6] D1 R/W [7] D2 R/W Table 51. Register 0x76—Extended Resolution 1 Bit Name R/W [3:2] V Read-only CCP [5:4] V Read-only this register is read, this register and the registers holding the MSB of each reading are frozen until read. ...
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... Pulses Counted (default [7:6] FAN4 R/W Sets number of pulses to be counted when measuring Fan 4 speed. Can be used to determine fan pulses per revolution for unknown fan type. Pulses Counted (default Rev Page ADT7473 ...
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... Twos complement = 1, sets the temperature range to twos complement temperature range. COMPL Twos complement = 0, changes the temperature range to Offset 64. When this bit is changed, the ADT7473 interprets all relevant temperature register values as defined by this bit. [1] TempOffset TempOffset = 0 sets offset range to ±64°C at 0.5°C resolution. ...
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... Table 60. Register 0x7F—Manufacturer’s Test Register 2 (Power-On Default = 0x00) Bit Name R/W Description [7:0] Reserved Read-only Manufacturer’s test register. These bits are reserved for manufacturer’s test purposes and should not be written to under normal operation. Rev Page ADT7473 ...
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... ADT7473ARQZ-REEL –40°C to +125°C 1 ADT7473ARQZ-REEL7 –40°C to +125°C EVAL-ADT7473EB Pb-free part © 2006 Analog Devices, Inc. All rights reserved. Trademarks and T registered trademarks are the property of their respective owners. 0.197 ...