ADT7468 Analog Devices, Inc., ADT7468 Datasheet
ADT7468
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ADT7468 Summary of contents
Page 1
... PWM fan controller for noise sensitive or power sensitive applications requiring active system cooling. The ADT7468 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 that they operate at the lowest possible speed for minimum acoustic noise ...
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... Step 10: High and Low Limits for Temperature Channels ... 53 Step 11: Monitoring THERM ................................................... 56 Step 12: Ramp Rate for Acoustic Enhancement..................... 57 Enhancing System Acoustics ........................................................ 60 Acoustic Enhancement Mode Overview ................................ 60 Register Tables ................................................................................ 62 ADT7468 Programming Block Diagram .................................... 81 Outline Dimensions ....................................................................... 82 Ordering Guide .......................................................................... 82 Changes to Ordering Guide ...................................................... 80 4/04—Revision 0: Initial Version Rev Page ...
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... RPM 85.5 90 94.5 kHz 83.7 90 96.3 kHz kHz Rev Page ADT7468 = 25°C and represent most likely parametric A . Timing specifications are tested at MIN Test Conditions/Comments Interface inactive, ADC active Standby mode 0°C ≤ T ≤ 70°C A −40°C ≤ T ≤ +100°C A −40°C ≤ T ≤ ...
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... ADT7468 Parameter OPEN-DRAIN DIGITAL OUTPUTS, PWM1 TO PWM3, XTO Current Sink Output Low Voltage High Level Output Current OPEN-DRAIN SERIAL DATA BUS OUTPUT (SDA) Output Low Voltage High Level Output Current SMBUS DIGITAL INPUTS (SCL, SDA) Input High Voltage, V ...
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... Exposure to absolute ±5 mA maximum rating conditions for extended periods may affect ±20 mA device reliability. 150°C Thermal Characteristics −65°C to +150°C 24-lead QSOP package: 220°C θ = 150°C/W JA 260°C θ = 39°C/W JC 300°C 1000 V Rev Page ADT7468 ...
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... V Power Supply. Can be powered by 3.3 V standby, if monitoring in low power states is required through this pin. The ADT7468 can also be powered from supply. Setting Bit 7 of Configuration Register 1 (Reg. 0x40) rescales the V 5 VID0 Digital Input (Open Drain). Voltage supply readouts from CPU. This value is read into the VID register (Reg. 0x43). ...
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... Analog Input. Monitors processor core voltage ( V). CCP 24 PWM1 Digital Output (Open Drain). Pulse width modulated output to control Fan 1 speed. Requires 10 kΩ typical pull-up. XTO Also functions as the output from the XOR tree in XOR test mode. Rev Page ADT7468 ...
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... ADT7468 TYPICAL PERFORMANCE CHARACTERISTICS 0 –10 –20 –30 –40 –50 – 2.2 3.3 CAPACITANCE (nF) Figure 4. Temperature Error vs. Capacitance between D+ and D− 0 –10 –20 –30 –40 –50 –60 –70 –80 –90 –100 CAPACITANCE (nF) Figure 5. External Temperature Error vs. D+/D− Capacitance GND 40 20 ...
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... POWER SUPPLY NOISE FREQUENCY (kHz) Figure 12. Remote Temperature Error vs. Power Supply Noise Frequency 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 –2.5 –3.0 –3.5 –4.0 5.0 5.2 5.4 –40 Figure 13. Internal Temperature Error vs. ADT7468 Temperature 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 –2.5 –3.0 –3.5 –4.0 –40 100M 1G Figure 14. Remote Temperature Error vs. ADT7468 Temperature 100M 1G Rev ...
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... Due to the inclusion of extra functionality, the register map has changed, including an additional configuration register: Configuration Register 5 at Address 0x7C. Configuration Register 5 Bit 0: If Bit 0 is set terms of temperature the ADT7468 is is disabled, writing to backward-compatible with the ADT7463. Measurements including the T the range of − ...
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... CHASSIS FAN AMBIENT TEMPERATURE CONTROLLER RECOMMENDED IMPLEMENTATION Configuring the ADT7468 as in Figure 15 allows the system designer to use the following features: • Two PWM outputs for fan control three fans (the front and rear chassis fans are connected in parallel). • Three TACH fan speed measurement inputs. ...
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... ADT7468 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 ADT7468 has a fixed 7-bit serial bus address of 0101110 or 0x2E. The read/write bit must be added to get the 8-bit address (01011100 or 0x5C). Data is sent over the serial bus in sequences of nine clock pulses: eight bits of data followed by an acknowledge bit from the slave device ...
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... The master asserts a stop condition on SDA and the transaction ends. For the ADT7468, the send byte protocol is used to write a register address to RAM for a subsequent single byte read from the same address. This operation is illustrated in Figure 19. Figure 19. Setting a Register Address for a Subsequent Read ...
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... SMBALERT is cleared only if the error condition is absent. SMBUS TIMEOUT The ADT7468 includes an SMBus timeout feature. If there is no SMBus activity for 35 ms, the ADT7468 assumes that the bus is locked and releases the bus. This prevents the device from locking or holding the SMBus expecting data. Some SMBus controllers cannot handle the SMBus timeout feature can be disabled ...
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... The ADT7468 has a VID code change detect function. When Pin 21 is configured as the VID5 input, VID code changes can be detected and reported back by the ADT7468. Bit 0 of Status Register 2 (Reg. 0x42) is the 12 V/VC bit and denotes a VID change when set. The VID code change bit is set when the logic states on the VID inputs are different than they were 11 μ ...
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... ADDITIONAL ADC FUNCTIONS FOR VOLTAGE MEASUREMENTS A number of other functions are available on the ADT7468 to offer the system designer increased flexibility. Turn-Off Averaging MUX For each voltage measurement read from a value register, 16 readings have actually been made internally and the results averaged before being placed into the value register ...
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... Setting Bit 6 of Configuration Register 2 (Reg. 0x73) places the ADT7468 into single-channel ADC conversion mode. In this mode, the ADT7468 can be made to read a single voltage channel only. If the internal ADT7468 clock is used, the selected input is read every 0.7 ms. The appropriate ADC channel is selected by writing to Bits <7:5> of the TACH1 minimum high byte register (0x55) ...
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... D+ input NPN transistor is used, the emitter is connected to the D– input and the base to the D+ input. Figure 25 and Figure 26 show how to connect the ADT7468 to an NPN or PNP transistor for temperature measurement. To prevent ground noise from interfering with the measurement, the more negative terminal of the sensor is not referenced to ground, but is biased above ground by an internal diode at the D– ...
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... The high current level of 1nF the ADT7468, I D– μA. If the ADT7468 current levels do not match LOW the current levels specified by the CPU manufacturer, it might be necessary to remove an offset. The CPU’s data sheet should advise whether this offset needs to be removed and how to calculate it ...
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... D+/D– lines. Constant high frequency noise usually attenuates or increases temperature measurements by a linear, constant value. The ADT7468 has temperature offset registers at Addresses 0x70 and 0x72 for the Remote 1 and Remote 2 temperature channels. By doing a one-time calibration of the system, the user can determine the offset caused by system board noise and null it using the offset registers ...
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... Reg. 0x53, Remote 2 temperature high limit = 0x7F default Reading Temperature from the ADT7468 It is important to note that temperature can be read from the ADT7468 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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... Alternatively, SMBALERT interrupts can be generated to flag a processor or micro- controller of out-of-limit conditions. 8-Bit Limits The following is a list of 8-bit limits on the ADT7468. Voltage Limit Registers Reg. 0x44, 2.5 V low limit = 0x00 default, Register 0x44 2.5 V low limit = 0x00 default Reg ...
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... VID code on the VID0 to VID5 inputs. INTERRUPTS SMBALERT Interrupt Behavior The ADT7468 can be polled for status SMBALERT interrupt can be generated for out-of-limit conditions important to note how the SMBALERT output and status bits behave when writing interrupt handler software. ...
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... ADT7468 HIGH LIMIT TEMPERATURE “STICKY” STATUS BIT TEMP BACK IN LIMIT (STATUS BIT STAYS SET) SMBALERT Figure 28. SMBALERT and Status Bit Behavior Figure 28 shows how the SMBALERT output and sticky status bits behave. Once a limit is exceeded, the corresponding status bit is set to 1. The status bit remains set until the error condition subsides and the status register is read ...
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... THERM pin. This can be useful for connecting to the PROCHOT output of a CPU to gauge system performance. The user can also set up the ADT7468 to run the fans at 100% whenever the THERM pin is driven low externally by setting the boost bit (Bit 2) in Configuration Register 3 (Address 0x78 ...
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... F4P bit is set. Generating SMBALERT Interrupts from THERM Timer Events The ADT7468 can generate SMBALERT s when a programma- ble THERM timer limit has been exceeded. This allows the system designer to ignore brief, infrequent THERM assertions while capturing longer THERM timer events. Register 0x7A is the THERM timer limit register ...
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... Configuring the THERM Pin as an Output In addition to monitoring THERM as an input, the ADT7468 can optionally drive THERM low as an output. In cases where PROCHOT is bidirectional, THERM can be used to throttle the 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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... In many cases, the 4-wire fan PWM input has a built-in pull-up resistor. The ADT7468 PWM frequency can be set to a selection of low frequencies or a single high PWM frequency. The low fre- quency options are usually used for 2-wire and 3-wire fans, while the high frequency option is usually used with 4-wire fans ...
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... Driving Two Fans from PWM3 The ADT7468 has four TACH inputs available for fan speed measurement, but only three PWM drive outputs fourth fan is being used in the system, it should be driven from the PWM3 output in parallel with the third fan. Figure 37 shows how to drive two fans in parallel using low cost NPN transistors ...
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... Driving 2-Wire Fans The ADT7468 can support 2-wire fans only when the low frequency PWM mode is selected in Configuration Register 5, Bit 2. If this bit is not set to 1, the ADT7468 cannot measure the speed of 2-wire fans. Figure 39 shows how a 2-wire fan can be connected to the ADT7468 ...
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... Reg. 0x2D, TACH3 high byte = 0x00 default V CC Reg. 0x2E, TACH4 low byte = 0x00 default Reg. 0x2F, TACH4 high byte = 0x00 default Reading Fan Speed from the ADT7468 FAN SPEED COUNTER The measurement of fan speeds involves a 2-register read for ADT7468 each measurement. The low byte should be read first. This causes the high byte to be frozen until both high and low byte registers have been read, preventing erroneous TACH readings ...
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... ADT7468 The fan tachometer reading registers report back the number of 11.11 μs period clocks (90 kHz oscillator) gated to the fan speed counter, from the rising edge of the first fan TACH pulse to the rising edge of the third fan TACH pulse (assuming two pulses per revolution are being counted). Because the device is essen- tially measuring the fan TACH period, the higher the count value, the slower the fan is actually running ...
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... Fan Speed Measurements (Low Frequency Mode Only) The ADT7468 is capable of measuring the speed of 2-wire fans, that is, fans without TACH outputs this, the fan must be interfaced as shown in the Driving 2-Wire Fans section. In this case, the TACH inputs should be reprogrammed as analog inputs, AIN ...
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... See the Programming the Automatic Fan Speed Control Loop section. In manual fan speed control mode, the ADT7468 allows the duty cycle of any PWM output to be manually adjusted. This can be useful if the user wants to change fan speed in the software or adjust PWM duty cycle output for test purposes. Bits < ...
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... ADT7468 is not addressed by any valid SMBus transaction before the fail-safe timeout (4.6 s) lapses, then the ADT7468 drives the fans to full speed. If the ADT7468 is addressed by a valid SMBus transaction after this point, the fans stop, and the ADT7468 assumes its default settings and begins normal operation ...
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... FAIL-SAFE TIMER ELAPSES AFTER THE FAIL-SAFE TIMEOUT HAS THE ADT7468 BEEN ACCESSED BY A VALID RUN THE FANS TO FULL SPEED N SMBUS TRANSACTION? Y HAS THE ADT7468 BEEN ACCESSED BY A VALID SMBUS TRANSACTION? START UP THE SWITCH OFF FANS ADT7468 NORMALLY Figure 48. Power-On Flow Chart CHECK V ...
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... PWM outputs. The three PWM outputs can be used to control up to four fans. The ADT7468 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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... ADT7468 DYNAMIC T CONTROL MODE MIN In addition to the automatic fan speed control mode described in the Automatic Fan Control Overview section, the ADT7468 has a mode that extends the basic automatic fan speed control loop. Dynamic T control allows the ADT7468 to intelligently 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. ADT7468 can self- adjust its fan control loop to maintain either an operating zone temperature or a system target temperature. For example, one can specify that the ambient temperature in a system should be maintained at 50° ...
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... This influences the choice of whether to use the TACH4 pin or to reconfigure it for the THERM function the CPU fan to be controlled using the ADT7468 or will it run at full speed 100% of the time runs at 100%, this frees up a PWM output, but the system is louder ...
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... Recommended Implementation 1 Configuring the ADT7468 as shown in Figure 54 provides the system designer with the following features: 1. Six VID inputs (VID0 to VID5) for VRM10 support. 2. Two PWM outputs for fan control three fans. (The front and rear chassis fans are connected in parallel.) 3 ...
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... ADT7468 Recommended Implementation 2 Configuring the ADT7468 as in Figure 55 provides the system designer with the following features: 1. Six VID inputs (VID0 to VID5) for VRM10 support. 2. Three PWM outputs for fan control three fans. (All three fans can be individually controlled.) 3. Three TACH fan speed measurement inputs. ...
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... RANGE PWM MIN 100% RAMP CONTROL (ACOUSTIC ENHANCEMENT) TACHOMETER 3 AND MEASUREMENT RANGE Figure 56. Assigning Temperature Channels to Fan Channels Rev Page ADT7468 PWM CONFIG PWM PWM1 GENERATOR TACH1 PWM CPU FAN SINK CONFIG PWM PWM2 GENERATOR TACH2 PWM CONFIG FRONT CHASSIS ...
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... ADT7468 Mux Configuration Example This is an example of how to configure the mux in a system using the ADT7468 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 behavior: • ...
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... MEASUREMENT RANGE PWM MIN 100% RAMP CONTROL (ACOUSTIC ENHANCEMENT) TACHOMETER 3 AND MEASUREMENT RANGE Figure 58. Understanding the T Parameter MIN Rev Page ADT7468 = 0x9A (90°C) MIN = 0x9A (90°C) MIN = 0x9A (90°C) MIN – MIN HYST . HYST – MIN HYST . HYST – T ...
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... ADT7468 STEP 4: PWM FOR EACH PWM (FAN) OUTPUT MIN PWM is the minimum PWM duty cycle at which each fan in MIN the system runs also the start speed for each fan under automatic fan control once the temperature rises above T For maximum system acoustic benefit, PWM low as possible ...
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... PWM duty cycle.) Determine the slope of the required control loop to meet these requirements. Using the ADT7468 evaluation software, you can graphically program and visualize this functionality. Ask your local Analog Devices representative for details. 100% ...
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... ADT7468 100% 50% 33% 25% 10% 0% 30°C 40°C 45°C 54°C T MIN Figure 64. Increasing PWM Changes Effective T MIN For a given T value, the temperature at which the fan runs RANGE at full speed for different PWM values can be easily MIN calculated (Max DC − Min DC) × T ...
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... T 16°C RANGE 20°C This example uses the MUX configuration described in Step 2, 26.6°C 32°C with the ADT7468 connected as shown in Figure 57. Both CPU 40°C temperature and VRM temperature drive the CPU fan 53.3°C connected to PWM1. Ambient temperature drives the front 80°C 100 ...
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... ADT7468 100 TEMPERATURE ABOVE T 100 TEMPERATURE ABOVE T Figure 67. T and % Fan Speed Slopes for VRM, Ambient, and RANGE CPU Temperature Channels STEP 7: T FOR TEMPERATURE CHANNELS ...
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... CPU FAN SINK CONFIG RAMP PWM PWM2 GENERATOR TACH2 PWM CONFIG FRONT CHASSIS RAMP PWM PWM3 GENERATOR TACH3 AND 4 REAR CHASSIS . Bits <7:5> of Enhanced MIN . If the fans are always on, the MIN value has no effect on the fan when the temperature drops . MIN ADT7468 ...
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... In response, the ADT7468 increases T fans off longer and to allow the temperature zone to get closer to the operating point. Likewise, too high a T the operating point to be exceeded, and in turn, the ADT7468 reduces T Programming Operating Point Registers There are three operating point registers, one for each temperature channel. These 8-bit registers allow the operating point temperatures to be programmed with 1° ...
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... T MIN Short Cycle and Long Cycle The ADT7468 implements two loops: a short cycle and a long cycle. The short cycle takes place every n monitoring cycles. The long cycle takes place every 2n monitoring cycles. The value programmable for each temperature channel. The bits are located at the following register locations: Remote 1 = CYR1 = Bits < ...
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... ADT7468 Local = CYL = Bits <5:3> of Calibration Control Register 2 (Address = 0x37). Remote 2 = CYR2 = Bits <7:6> of Calibration Control Register 2 and Bit 0 of Calibration Control Register 1 (Address = 0x36). Table 16. Cycle Bit Assignments Duration Code Short Cycle (sec) Long Cycle 000 8 cycles 1 16 cycles 001 16 cycles 2 32 cycles ...
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... T can go. MIN is below the operating point temperature The dynamic T MIN . MIN NO CHANGE IN T HERE MIN DUE TO ANY CYCLE, BECAUSE T1(n) – – 1) ≤ 0.25°C AND T1(n) < > T MIN STAYS THE SAME MIN ADT7468 is never MIN should MIN control MIN ...
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... The operating point for the processor can be determined by allowing the current temperature to be copied to the operating point register when the PROCHOT output pulls the THERM input low on the ADT7468. This gives the maximum temperature at which the Pentium 4 can run before clock modulation occurs. ...
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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 ADT7468 into manual mode and changing the PWM output from 0% to 100% PWM duty cycle. The PWM output takes 35 secs to reach 100%, when a ramp rate of one ...
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... Slower Ramp Rates 60 The ADT7468 can be programmed for much longer ramp times 40 by slowing the ramp rates. Each ramp rate can be slowed by a factor PWM1 Configuration Register (Reg. 0x5C) 0 17.6 <3> slow, 1 slows the ramp rate for PWM1 by 4. ...
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... ACOU2, selects the ramp rate for PWM2. 000 = 140 sec 001 = 70.4 sec 010 = 47.2 sec 011 = 28 sec 100 = 17.6 sec 101 = 12 sec 110 = 6.4 sec 111 = 3.2 sec Rev Page ADT7468 ...
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... Figure 82. Acoustic Enhancement Smoothes Fan Speed Variations under Automatic Fan Speed Control ACOUSTIC ENHANCEMENT MODE OVERVIEW Figure 82 gives a top-level overview of the automatic fan control circuitry on the ADT7468 and shows where acoustic enhance- ment fits in. Acoustic enhancement is intended as a postdesign tweak made by a system or mechanical engineer evaluating best settings for the system ...
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... Approaches to System Acoustic Enhancement There are two different approaches to implementing system acoustic enhancement: temperature-centric and fan-centric. The ADT7468 uses the fan-centric approach. The temperature-centric approach involves smoothing transient temperatures as they are measured by a temperature source (for example, Remote 1 temperature). The temperature values used to calculate the PWM duty cycle values are smoothed, reducing fan speed variation ...
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... ADT7468 REGISTER TABLES Table 17. Register Map Address R/W Description Bit 7 0x20 R 2 measurement 0x21 R V measurement 9 CCP 0x22 R V measurement 9 CC 0x23 measurement 9 0x24 measurement 9 0x25 R Remote 1 9 Temperature 0x26 R Local Temperature 9 0x27 R Remote 2 9 Temperature 0x28 R TACH1 Low Byte ...
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... EN1 ACOU2 ACOU2 ACOU2 EN3 Rev Page ADT7468 Bit 2 Bit 1 Bit 0 Default 0xFF 0x00 0xFF 0x01 0x7F 0x01 0x7F 2 ...
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... MSB reading registers are frozen until read. Both the extended resolution registers and the MSB registers are frozen Low (Bit 1 of the Dynamic T Control Register 1, 0x36) is set, V CCP MIN 3 V (Pin 4) is the supply voltage for the ADT7468. CC Bit 6 Bit 5 Bit 4 Bit ...
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... Failed (internal circuitry destroyed). • Not populated. (The ADT7468 expects to see a fan connected to each TACH fan is not connected to that TACH, its TACH minimum high and low bytes should be set to 0xFFFF.) • Alternate function, for example, TACH4 reconfigured as THERM pin. ...
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... ADT7468 Table 23. Register 0x36—Dynamic T MIN Bit Name R/W Description <0> CYR2 Read/write MSB of 3-bit remote 2 cycle value. The other two bits of the code reside in Dynamic T (Reg. 0x37). These three bits define the delay time between making subsequent T control loop, in terms of the number of monitoring cycles. The system has associated thermal time constants that need to be found to optimize the response of fans and the control loop. < ...
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... Description Maximum duty cycle for PWM1 output, default = 100% (0xFF). Maximum duty cycle for PWM2 output, default = 100% (0xFF). Maximum duty cycle for PWM3 output, default = 100% (0xFF). Rev Page ADT7468 1 Increase Cycle 16 cycles (2 sec) 32 cycles (4 sec) 64 cycles (8 sec) ...
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... Logic 1 disables fan spin-up for two TACH pulses. Instead, the PWM outputs go high for the entire fan spin-up timeout selected. <6> TODIS Read/write When this bit is set to 1, the SMBus timeout feature is enabled. This allows the ADT7468 to be used with SMBus controllers that cannot handle SMBus timeouts. (lockable.) <7> V Read/write ...
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... Description Power-On Default 2.5 V 0x00 2.5 V 0xFF V low limit 0x00 CCP V high limit 0xFF CCP V low limit 0x00 CC V high limit 0xFF low limit 0x00 5 V high limit 0xFF 12 V low limit 0x00 12 V high limit 0xFF Rev Page ADT7468 . HYST ...
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... ADT7468 Table 31. Temperature Limit Registers Register Address R/W 0x4E Read/write 0x4F Read/write 0x50 Read/write 0x51 Read/write 0x52 Read/write 0x53 Read/write 1 Exceeding any of these temperature limits by 1°C causes the appropriate status bit to be set in the interrupt status register. Setting the Configuration Register 1 lock bit has no effect on these registers ...
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... Remote 2 temperature controls PWMx. 110 = fastest speed calculated by all three temperature channel controls PWMx. 111 = manual mode. PWM duty cycle registers (Reg. 0x30 to Reg. 0x32) become writable. Rev Page ADT7468 Power-On Default 0x82 0x82 0x82 ...
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... ADT7468 Table 35. TEMP T /PWM Frequency Registers RANGE 1 Register Address R/W 0x5F Read/write 0x60 Read/write 0x61 Read/write Bit Name R/W <2:0> FREQ Read/write <3> THRM Read/write <7:4> RANGE Read/write 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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... SYNC = 0 synchronizes only TACH3 and TACH4 to PWM3 output. <5> MIN1 Read/write When the ADT7468 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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... Register Address R/W 0x64 Read/write 0x65 Read/write 0x66 Read/write 1 Bit Name R/W <7:0> PWM duty cycle Read/write 1 These registers become read-only when the ADT7468 is in automatic fan control mode. 1 Table 39. T Registers MIN 2 Register Address R/W 0x67 Read/write 0x68 Read/write 0x69 Read/write 1 These are the T registers for each temperature channel ...
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... Remote 1 temperature reading. This is to compensate for any inherent system offsets such as PCB trace resistance. LSB value = 0.5°C. Rev Page ADT7468 Power-On Default 0x64 (100°C) 0x64 (100°C) 0x64 (100°C) Power-On Default 0x44 control loops ...
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... It is possible to remove attenuators from individual channels using Bits <7:4> of Configuration Register 4 (0x7D). CONV = 1, the ADT7468 is put into a single-channel ADC conversion mode. In this mode, the ADT7468 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 < ...
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... Remote 1 temperature LSBs. Holds the 2 LSBs of the 10-bit Remote 1 temperature measurement. Local temperature LSBs. Holds the 2 LSBs of the 10-bit local temperature measurement. Remote 2 temperature LSBs. Holds the 2 LSBs of the 10-bit Remote 2 temperature measurement. Rev Page channel. CCP channel. CC measurement. CCP measurement. CC ADT7468 ...
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... ADT7468 Table 51. Register 0x78—Configuration Register 3 (Power-On Default = 0x00) 1 Bit Name R/W <0> ALERT Read/write <1> THERM Read/write <2> BOOST Read/write <3> FAST Read/write <4> DC1 Read/write <5> DC2 Read/write <6> DC3 Read/write <7> DC4 Read/write 1 This register becomes read-only when the Configuration Register 1 lock bit is set to 1. Any further attempts to write to this register have no effect. ...
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... Read/write 2sC = 1, sets the temperature range to twos complement temperature range. 2sC = 0, changes the temperature range to Offset 64. When this bit is changed, the ADT7468 interprets all relevant temperature register values as defined by this bit. <1> HF/LF Sets the PWM drive frequency to high frequency mode (0) or low frequency mode (1). ...
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... ADT7468 Table 56. Register 0x7D—Configuration Register 4 (Power-On Default = 0x00) 1 Bit Name R/W Description <1:0> PIN14FUNC Read/write These bits set the functionality of Pin 14: <3:2> AINL Read/write These two bits define the input threshold for 2-wire fan speed measurements (low frequency mode only): <4> BpAtt2.5V Bypass 2.5 V attenuator. When set, the measurement scale for this channel changes from 0 V (0x00) to 2.2965 V (0xFF). < ...
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... PROGRAMMING BLOCK DIAGRAM SPEED Figure 85. Rev Page ADT7468 FAN CYCLE/RELATIVE DUTY PWM ...
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... Model Temperature Range ADT7468ARQ –40°C to +120°C ADT7468ARQ-REEL –40°C to +120°C ADT7468ARQ-REEL7 –40°C to +120°C ADT7468ARQZ 1 –40°C to +120°C ADT7468ARQZ-REEL –40°C to +120°C ADT7468ARQZ-REEL7 –40°C to +120°C EVAL-ADT7468EB Pb-free part. 0.341 BSC 24 13 0.154 BSC 0 ...
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... NOTES Rev Page ADT7468 ...
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... ADT7468 NOTES © 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04499–0–7/05(A) Rev Page ...