ADT7484A/ADT7486A Digital Temperature Sensor with SST Interface The ADT7484A/ADT7486A are simple digital temperature sensors for use in PC applications with a Simple Serial Transport (SST) interface. These devices can monitor their own temperature as well as the temperature of one (ADT7484A) or two (ADT7486A) remote sensor diodes. The ADT7484A/ADT7486A are controlled by a single SST bidirectional data line. The devices are fixed-address SST clients where the target address is chosen by the state of the two address pins, ADD0 and ADD1. http://onsemi.com MARKING DIAGRAMS 8 Features • • • • 1 1 On-Chip Temperature Sensor 1 or 2 Remote Temperature Sensors Simple Serial Transportt (SSTt) Interface Rev 1 Compliant These are Pb−Free Devices T7484A ALYWG G SOIC−8 CASE 751 1 A L Y W G = Assembly Location = Wafer Lot = Year = Work Week = Pb−Free Package Applications 8 • Personal Computers • Portable Personal Devices • Industrial Sensor Nets 1 T20 AYWG G MSOP−8 CASE 846AB 1 10 1 T2x A Y W G T22 AYWG G MSOP−10 CASE 846AC 1 = Specific Device Code = Assembly Location = Year = Work Week = Pb−Free Package (Note: Microdot may be in either location) PIN ASSIGNMENTS VCC 1 8 SST GND 2 7 ADD0 6 RESERVED 5 ADD1 VCC 1 10 SST GND 2 9 ADD0 8 RESERVED D1– 4 7 ADD1 D2+ 5 6 D2– D1+ 3 ADT7484A D1– 4 (Top View) D1+ 3 ADT7486A (Top View) ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page 11 of this data sheet. © Semiconductor Components Industries, LLC, 2009 December, 2009 − Rev. 4 1 Publication Order Number: ADT7484A−86A/D ADT7484A/ADT7486A ON−CHIP TEMPERATURE SENSOR A/D CONVERTER D1+ D1– (ADT7486A ONLY) D2+ DIGITAL MUX LOCAL TEMPERATURE VALUE REGISTER ANALOG MUX SST INTERFACE SST REMOTE TEMPERATURE VALUE REGISTER D2– ADT7484A/ ADT7486A VDD OFFSET REGISTERS GND ADD1 ADDRESS SELECTION ADD0 RESERVED Figure 1. Functional Block Diagram ABSOLUTE MAXIMUM RATINGS Parameter Rating Unit Supply Voltage (VCC) 3.6 V Voltage on Any Other Pin (Including SST Pin) 3.6 V Input Current at Any Pin ±5.0 mA Package Input Current ±20 mA Maximum Junction Temperature (TJ max) 150 °C −65 to +150 °C Storage Temperature Range Lead Temperature, Soldering IR Reflow Peak Temperature Lead Temperature, Soldering (10 sec) °C 260 300 ESD Rating 1500 V Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. NOTE: This device is ESD sensitive. Use standard ESD precautions when handling. THERMAL CHARACTERISTICS Package Type 8−Lead MSOP and 8−Lead SOIC NB Packages (ADT7484A) 10−Lead MSOP (ADT7486A) NOTE: qJA qJC Unit 206 44 °C/W qJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. http://onsemi.com 2 ADT7484A/ADT7486A ADT7484A PIN ASSIGNMENT Pin No. Mnemonic Type Description 1 VCC Power supply 3.3 V ± 10%. 2 GND Ground Ground Pin. 3 D1+ Analog input Positive Connection to Remote Temperature Sensor. 4 D1− Analog input Negative Connection to Remote Temperature Sensor. 5 ADD1 Digital input SST Address Select. 6 RESERVED Reserved Connect to Ground. 7 ADD0 Digital input SST Address Select. 8 SST Digital input/output SST Bidirectional Data Line. ADT7486A PIN ASSIGNMENT Pin No. Mnemonic Type Description 1 VCC Power supply 3.3 V ± 10%. 2 GND Ground Ground Pin. 3 D1+ Analog input Positive Connection to Remote 1 Temperature Sensor. 4 D1− Analog input Negative Connection to Remote 1 Temperature Sensor. 5 D2+ Analog input Positive Connection to Remote 2 Temperature Sensor. 6 D2− Analog input Negative Connection to Remote 2 Temperature Sensor. 7 ADD1 Analog input SST Address Select. 8 RESERVED Analog input Connect to Ground. 9 ADD0 Digital input SST Address Select. 10 SST Digital input/output SST Bidirectional Data Line. ELECTRICAL CHARACTERISTICS (TA = TMIN to TMAX, = VCC = VMIN to VMAX, unless otherwise noted) Parameter Conditions Min Typ Max Unit 3.0 3.3 3.6 V Power Supply Supply Voltage, VCC Undervoltage Lockout Threshold Average Operating Supply Current, IDD 2.8 V Continuous conversions 3.8 5.0 mA 40°C ≤ TA ≤ 70°C, VCC = 3.3 V ±5% +1.0 ±1.75 °C −40°C ≤ TA ≤ +100°C ±4.0 °C −40°C ≤ TD ≤ +125°C; TA = 25°C; VCC = 3.3 V ±1.0 °C ±1.75 °C ±4.0 °C Temperature-to-Digital Converter Local Sensor Accuracy Remote Sensor Accuracy −40°C ≤ TD ≤ +125°C; −40 ≤ TA ≤ 70°C, VCC = 3.3 V ±5% +1.0 −40°C ≤ TD ≤ +125°C; −40 ≤ TA ≤ +100°C Remote Sensor Source Current Low level Mid level High level Resolution Series Resistance Cancellation The ADT7484A and ADT7486A cancel 1.5 kW in series with the remote thermal diode 1. Guaranteed by design, not production tested. 2. Minimum and maximum bit times are relative to tBIT defined in the timing negotiation pulse. 3. Devices compatible with hold time specification as driven by SST originator. http://onsemi.com 3 12 80 204 mA 0.016 °C 1.5 kW ADT7484A/ADT7486A ELECTRICAL CHARACTERISTICS (TA = TMIN to TMAX, = VCC = VMIN to VMAX, unless otherwise noted) Parameter Conditions Min Typ Max Unit 12 12 ms Temperature-to-Digital Converter Conversion Time (Local Temperature) (Note 1) Averaging enabled Conversion Time (Remote Temperature) (Note 1) Averaging enabled 38 ms Total Monitoring Cycle Time (Note 1) Averaging enabled 50 ms Digital Inputs (ADD0, ADD1) Input High Voltage, VIH 2.3 V Input Low Voltage, VIL 0.8 Input High Current, IIH VIN = VCC Input Low Current, IIL VIN = 0 −1.0 mA 1.0 Pin Capacitance V 5.0 mA pF Digital I/O (SST Pin) 1.1 Input High Voltage, VIH V Input Low Voltage, VIL 0.4 150 V Hysteresis (Note 1) Between input switching levels Output High Voltage, VOH ISOURCE = 6 mA (maximum) 1.9 V High Impedance State Leakage, ILEAK Device powered on SST bus; VSST = 1.1 V, VCC = 3.3 V ±1.0 mA High Impedance State Leakage, ILEAK Device unpowered on SST bus; VSST = 1.1 V, VCC = 0 V ±10 mA Signal Noise Immunity, VNOISE Noise glitches from 10 MHz to 100 MHz; width up to 50 ns 1.1 mV 300 mV p-p SST Timing 0.495 Bitwise Period, tBIT High Level Time for Logic 1, tH1 (Note 2) tBIT defined in speed negotiation High Level Time for Logic 0, tH0 (Note 2) 500 ms 0.6 x tBIT 0.75 x tBIT 0.8 x tBIT ms 0.2 x tBIT 0.25 x tBIT 0.4 x tBIT ms 0.2 x tBIT ms 0.5 x tBIT−M ms 2 x tBIT ms 0.4 ms Time to Assert SST High for Logic 1, tSU, HIGH Hold Time, tHOLD (Note 3) See SST Specification Rev 1.0 Stop Time, tSTOP Device responding to a constant low level driven by originator 1.25 x tBIT 2 x tBIT Time to Respond After a Reset, tRESET Response Time to Speed Negotiation After Powerup Time after powerup when device can participate in speed negotiation 1. Guaranteed by design, not production tested. 2. Minimum and maximum bit times are relative to tBIT defined in the timing negotiation pulse. 3. Devices compatible with hold time specification as driven by SST originator. http://onsemi.com 4 500 ms ADT7484A/ADT7486A TYPICAL CHARACTERISTICS 1.55 3.56 3.55 1.50 3.53 1.45 DEV2 3.52 1.40 IDD (mA) SST O/P (V) DEV3 3.54 750Ω (~2mA) 270Ω (~5.2mA) 1.35 3.51 3.50 3.49 1.30 3.48 120Ω (~10.6mA) DEV1 3.47 1.25 3.46 1.20 2.6 2.8 3.0 3.2 3.4 3.45 –45 3.6 –25 –5 15 VCC (V) Figure 2. SST O/P Level vs. Supply Voltage 55 75 95 115 Figure 3. Supply Current vs. Temperature 7 1.55 6 1.50 5 750Ω (~2mA) 1.45 4 SST O/P (V) TEMPERATURE ERROR (5C) 35 TEMPERATURE (5C) HI SPEC (VCC = 3V) 3 2 MEAN (VCC = 3.3V) 270Ω (~5.2mA) 1.40 1.35 1.30 1 1.25 0 –1 –60 LO SPEC (VCC = 3.6V) –40 –20 0 20 40 60 80 100 120 120Ω (~10.6mA) 1.20 –50 140 0 50 100 150 TEMPERATURE (5C) TEMPERATURE (5C) Figure 4. Local Temperature Error Figure 5. SST O/P Level vs. Temperature 3.9 7 6 TEMPERATURE ERROR (5C) 3.7 IDD (mA) DEV2 DEV3 3.5 DEV1 3.3 3.1 2.9 2.65 5 4 3 2 HI SPEC (VCC = 3V) 1 MEAN (VCC = 3.3V) LO SPEC (VCC = 3.6V) 2.85 3.05 3.25 3.45 –2 –60 3.65 VCC (V) –40 –20 0 20 40 60 80 100 120 TEMPERATURE (5C) Figure 6. Supply Current vs. Voltage Figure 7. Remote Temperature Error http://onsemi.com 5 140 ADT7484A/ADT7486A TYPICAL CHARACTERISTICS 15 30 D+ TO GND ERROR (°C) 5 ć10 D+ TO VCC ć15 ć20 DEV1_EXT1 DEV1_EXT2 DEV2_EXT1 DEV1_EXT1 DEV1_EXT2 DEV2_EXT1 DEV2_EXT2 DEV3_EXT1 DEV3_EXT2 25 TEMPERATURE ERROR (5C) 10 DEV2_EXT2 DEV3_EXT1 DEV3_EXT2 ć25 –30 20 100mV 15 60mV 10 5 40mV 0 –35 –40 0 20 40 60 –5 10k 100 80 100k RESISTANCE (MΩ) 1M 10M 1G 100M NOISE FREQUENCY (5C) Figure 8. Remote Temperature Error vs. PCB Resistance Figure 9. Temperature Error vs. Common-Mode Noise Frequency 20 0 –10 –20 10 –30 ERROR (5C) TEMPERATURE ERROR (5C) 15 5 125mV EXT2 ć40 EXT1 ć50 –60 0 50mV ć70 −5 ć80 –10 10k 100k 1M 10M 100M –90 1G 0 10 POWER SUPPLY NOISE FREQUENCY (Hz) Figure 10. Local Temperature Error vs. Power Supply Noise 40 50 5 40mV 4 TEMPERATURE ERROR (5C) 6 TEMPERATURE ERROR (5C) 30 Figure 11. Remote Temperature Error vs. Capacitance Between D1+ and D1− 7 5 4 3 20mV 2 1 3 2 1 125mV 0 50mV –1 –2 10mV 0 10k 20 CAPACITANCE (nF) 100k 1M 10M 100M –3 10k 1G 100k 1M 10M 100M 1G POWER SUPPLY NOISE FREQUENCY (Hz) NOISE FREQUENCY (5C) Figure 12. Temperature Error vs. Differential-Mode Noise Frequency Figure 13. Remote Temperature Error vs. Power Supply Noise http://onsemi.com 6 ADT7484A/ADT7486A Product Description ADT7486A to distinguish between three input states: high, low (GND), and floating. The address range for fixed address, discoverable devices is 0x48 to 0x50. The ADT7484A is a single remote temperature sensor, and the ADT7486A is a dual temperature sensor for use in PC applications. The ADT7484A/ADT7486A accurately measure local and remote temperature and communicate over a one-wire Simple Serial Transport (SST) bus interface. Table 1. ADT7484A/ADT7486A Selectable Addresses SST Interface Simple Serial Transport (SST) is a one-wire serial bus and a communications protocol between components intended for use in personal computers, personal handheld devices, or other industrial sensor nets. The ADT7484A/ADT7486A support SST specification Rev 1. SST is a licensable bus technology from Analog Devices, Inc., and Intel Corporation. To inquire about obtaining a copy of the Simple Serial Transport Specification or an SST technology license, please email Analog Devices, at [email protected] or write to Analog Devices, 3550 North First Street, San Jose, CA 95134, Attention: SST Licensing, M/S B7-24. ADD1 ADD0 Address Selected Low (GND) Low (GND) 0x48 Low (GND) Float 0x49 Low (GND) High 0x4A Float Low (GND) 0x4B Float Float 0x4C Float High 0x4D High Low (GND) 0x4E High Float 0x4F High High 0x50 Command Summary Table 7 summarizes the commands supported by the ADT7484A/ADT7486A devices when directed at the target address selected by the fixed address pins. It contains the command name, command code (CC), write data length (WL), read data length (RL), and a brief description. ADT7484A/ADT7486A Client Address The client address for the ADT7484A/ADT7486A is selected using the address pin. The address pin is connected to a float detection circuit, which allows the ADT7484A/ Table 2. Command Code Summary Command Command Code, CC Write Length, WL Read Length, RL Description Ping() 0x00 0x00 0x00 Shows a nonzero FCS over the header if present. GetIntTemp() 0x00 0x01 0x02 Shows the temperature of the device’s internal thermal diode. GetExt1Temp() 0x01 0x01 0x02 Shows the temperature of External Thermal Diode 1. GetExt2Temp() 0x02 0x01 0x02 Shows the temperature of External Thermal Diode 2 (ADT7486A only). GetAllTemps() 0x00 0x01 0x04 (ADT7484A) 0x06 (ADT7486A) Shows a 4- or 6-byte block of data (ADT7484A: GetIntTemp, GetExt1Temp; ADT7486A: GetIntTemp, GetExt1Temp, GetExt2Temp). SetExt1Offset() 0xe0 0x03 0x00 Sets the offset used to correct errors in External Diode 1. GetExt1Offset() 0xe0 0x01 0x02 Shows the offset that the device is using to correct errors in External Diode 1. SetExt2Offset() 0xe1 0x03 0x00 Sets the offset used to correct errors in External Diode 2 (ADT7486A only). GetExt2Offset() 0xe1 0x01 0x02 Shows the offset that the device is using to correct errors in External Diode 2 (ADT7486A only). ResetDevice() 0xf6 0x01 0x00 Functional reset. The ADT7484A/ADT7486A also respond to this command when directed to the Target Address 0x00. GetDIB() 0xf7 0xf7 0x01 0x01 0x08 0x10 Shows information used by SW to identify the device’s capabilities. Can be in 8- or 16-byte format. http://onsemi.com 7 ADT7484A/ADT7486A Command Code Details Table 5. Reset Device() Command ADT7484A/ADT7486A Device Identifier Block The GetDIB() command retrieves the device identifier block (DIB), which provides information to identify the capabilities of the ADP7484A/ADT7486A. The data returned can be in 8− or 16−byte format. The full 16−bytes of DIB is detailed in Table 3. The 8-byte format involves the first eight bytes described in this table. Byte-sized data is returned in the respective fields as it appears in Table 3. Word-sized data, including vendor ID, device ID, and data values use little endian format, that is, the LSB is returned first, followed by the MSB. Name Value Device Capabilities 0xc0 Fixed address device 1 Version/ Revision 0x10 Meets Version 1 of the SST specification 2, 3 Vendor ID 00x11d4 Contains company ID number in little endian format 4, 5 Device ID 0x7484 or 0x7486 Contains device ID number in little endian format 6 Device Interface 0x01 SST device 7 Function Interface 0x00 Reserved 8 Reserved 0x00 Reserved Read Length Reset Command Device Address 0x01 0x00 0xf6 FCS The ADT7484A/ADT7486A show the local temperature of the device in response to the GetIntTemp() command. The data has a little endian, 16-bit, twos complement format. GetExtTemp() Prompted by the GetExtTemp() command, the ADT7484A/ADT7486A show the temperature of the remote diode in little endian, 16-bit, twos complement format. The ADT7484A/ADT7486A show 0x8000 in response to this command if the external diode is an open or short circuit. Description 0 Write Length GetIntTemp() Table 3. DIB Byte Details Byte Target Address GetAllTemps() The ADT7484A shows the local and remote temperatures in a 4-byte block of data (internal temperature first, followed by External Temperature 1) in response to a GetAllTemps() command. The ADT7486A shows the local and remote temperatures in a 6-byte block of data (internal temperature first, followed by External Temperature 1 and External Temperature 2) in response to this command. SetExtOffset() 9 Reserved 0x00 Reserved 10 Reserved 0x00 Reserved This command sets the offset that the ADT7484A/ ADT7486A will use to correct errors in the external diode. The offset is set in little endian, 16-bit, twos complement format. The maximum offset is ±128°C with +0.25°C resolution. 11 Reserved 0x00 Reserved GetExtOffset() 12 Reserved 0x00 Reserved 13 Reserved 0x00 Reserved 14 Revision ID 0x05 Contains revision ID 15 Client Device Address This command causes the ADT7484A/ADT7486A to show the offset that they are using to correct errors in the external diode. The offset value is returned in little endian format, that is, LSB before MSB. 0x48 to 0x50 Dependent on the state of the address pins ADT7484A/ADT7486A Response to Unsupported Commands Ping() A full list of command codes supported by the ADT7484A/ADT7486A is given in Table 7. The offset registers (Command Codes 0xe0 and 0xe1) are the only registers that the user can write to. The other defined registers are read only. Writing to Register Addresses 0x03 to 0xdf shows a valid FSC, but no action is taken by the ADT7484A/ADT7486A. The ADT7484A/ADT7486A show an invalid FSC if the user attempts to write to the devices between Command Codes 0xe2 to 0xee and no data is written to the device. These registers are reserved for the manufacturer’s use only, and no data can be written to the device via these addresses. The Ping() command verifies if a device is responding at a particular address. The ADT7484A/ADT7486A show a valid nonzero FCS in response to the Ping() command when correctly addressed. Table 4. Ping() Command Target Address Write Length Read Length Device Address 0x00 0x00 FCS ResetDevice() This command resets the register map and conversion controller. The reset command can be global or directed at the client address of the ADT7484A/ADT7486A. http://onsemi.com 8 ADT7484A/ADT7486A Temperature Measurement calculated using the two DVBE measurements. This method can also cancel the effect of series resistance on the temperature measurement. The resulting DVBE waveforms are passed through a 65 kHz low-pass filter to remove noise and then through a chopper-stabilized amplifier to amplify and rectify the waveform, producing a dc voltage proportional to DVBE. The ADC digitizes this voltage, and a temperature measurement is produced. To reduce the effects of noise, digital filtering is performed by averaging the results of 16 measurement cycles for low conversion rates. Signal conditioning and measurement of the internal temperature sensor is performed in the same manner. The ADT7484A/ADT7486A each have two dedicated temperature measurement channels: one for measuring the temperature of an on-chip band gap temperature sensor, and one for measuring the temperature of a remote diode, usually located in the CPU or GPU. The ADT7484A monitors one local and one remote temperature channel, whereas the ADT7486A monitors one local and two remote temperature channels. Monitoring of each of the channels is done in a round-robin sequence. The monitoring sequence is in the order shown in Table 11. Table 6. Temperature Monitoring Sequence Channel Number VDD Measurement Conversion Time (ms) 0 Local Temperature 12 1 Remote Temperature 1 38 2 Remote Temperature 2 (ADT7486A only) 38 I REMOTE SENSING TRANSISTOR N1 x I N2 x I IBIAS D+ VOUT+ C1* TO ADC D– BIAS DIODE LOW−PASS FILTER fC = 65kHz VOUT– *CAPACITOR C1 IS OPTIONAL. IT SHOULD ONLY BE USED IN NOISY ENVIRONMENTS. Temperature Measurement Method A simple method for measuring temperature is to exploit the negative temperature coefficient of a diode by measuring the base-emitter voltage (VBE) of a transistor operated at constant current. Unfortunately, this technique requires calibration to null the effect of the absolute value of VBE, which varies from device to device. The technique used in the ADT7484A/ADT7486A measures the change in VBE when the device is operated at three different currents. Figure 16 shows the input signal conditioning used to measure the output of a remote temperature sensor. This figure shows the remote sensor as a substrate transistor, which is provided for temperature monitoring on some microprocessors, but it could also be a discrete transistor. If a discrete transistor is used, the collector is not grounded and should be linked to the base. 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 D1− input. If the sensor is operating in an extremely noisy environment, C1 can be added as a noise filter. Its value should not exceed 1000 pF. To measure DVBE, the operating current through the sensor is switched between three related currents. Figure 16 shows N1 x I and N2 x I as different multiples of the current I. The currents through the temperature diode are switched between I and N1 x I, giving DVBE1, and then between I and N2 x I, giving DVBE2. The temperature can then be Figure 14. Signal Conditioning for Remote Diode Temperature Sensors Reading Temperature Measurements The temperature measurement command codes are detailed in Table 12. The temperature data returned is two bytes in little endian format, that is, LSB before MSB. All temperatures can be read together by using Command Code 0x00 with a read length of 0x04. The command codes and returned data are described in Table 12. Table 7. Temperature Channel Command Codes Temp Channel Returned Data Internal 0x00 LSB, MSB External 1 0x01 LSB, MSB External 2 0x02 LSB, MSB All Temps 0x00 Internal LSB, Internal MSB; External 1 LSB, External 1 MSB; External 2 LSB, External 2 MSB http://onsemi.com 9 Command Code ADT7484A/ADT7486A SST Temperature Sensor Data Format The data for temperature is structured to allow values in the range of ±512°C to be reported. Thus, the temperature sensor format uses a twos complement, 16-bit binary value to represent values in this range. This format allows temperatures to be represented with approximately a 0.016°C resolution. • • Table 8. SST Temperature Data Format Temperature (5C) Twos Complement MSB −125 −80 −40 −20 −5 −1 0 +1 +5 +20 +40 +80 +125 1110 0000 1110 1100 1111 0110 1111 1011 1111 1110 1111 1111 0000 0000 0000 0000 0000 0001 0000 0100 0000 1010 0001 0100 0001 1111 GND D+ 1100 0000 0000 0000 0000 0000 0011 1110 1100 0000 1100 0000 0000 0000 0100 0000 0100 0000 1100 0010 0000 0000 0000 0000 0100 0000 ADT7484A/ ADT7486A D– D+ 2N3906 PNP 5MIL 5MIL D– 5MIL 5MIL GND 5MIL Figure 16. Arrangements of Signal Tracks • Try to minimize the number of copper/solder joints, which can cause thermocouple effects. Where copper/solder joints are used, make sure that they are in both the D1+ and D1− paths and are at the same temperature. • Thermocouple effects should not be a major problem because 1°C corresponds to about 240 mV, and thermocouple voltages are about 3 mV/°C of the temperature difference. Unless there are two thermocouples with a big temperature differential between them, thermocouple voltages should be much less than 200 mV. • Place a 0.1 mF bypass capacitor close to the device. • If the distance to the remote sensor is more than eight inches, the use of a twisted-pair cable is recommended. This works for distances of about 6 to 12 feet. • For very long distances (up to 100 feet), use shielded twisted-pair cables, such as Belden #8451 microphone cables. Connect the twisted-pair cable to D1+ and D1− and the shield to GND, close to the device. Leave the remote end of the shield unconnected to avoid ground loops. Because the measurement technique uses switched current sources, excessive cable and/or filter capacitance can affect the measurement. When using long cables, the filter capacitor can be reduced or removed. Cable resistance can also introduce errors. A 1 W series resistance introduces about 0.5°C error. If a discrete transistor is used, the collector is not grounded and should be linked to the base. If a PNP transistor is used, the base is connected to the D1− input and the emitter is connected to the D1+ input. If an NPN transistor is used, the emitter is connected to the D1− input and the base is connected to the D1+ input. Figure 17 shows how to connect the ADT7484A/ADT7486A 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 D1− input. D+ 5MIL 5MIL LSB Using Discrete Transistors 2N3904 NPN such as clock generators, data/address buses, and CRTs, are avoided, this distance can be four to eight inches. Route the D1+ and D1− tracks close together in parallel with grounded guard tracks on each side. Provide a ground plane under the tracks if possible. Use wide tracks to minimize inductance and reduce noise pickup. A 5 mil track minimum width and spacing is recommended. ADT7484A/ ADT7486A D– Figure 15. Connections for NPN and PNP Transistors The ADT7484A/ADT7486A show an external temperature value of 0x8000 if the external diode is an open or short circuit. Layout Considerations Digital boards can be electrically noisy environments. Take the following precautions to protect the analog inputs from noise, particularly when measuring the very small voltages from a remote diode sensor: • Place the device as close as possible to the remote sensing diode. Provided that the worst noise sources, http://onsemi.com 10 ADT7484A/ADT7486A Temperature Offset Application Schematics As CPUs run faster, it is more difficult to avoid high frequency clocks when running the D1+ and D1− tracks around a system board. Even when the recommended layout guidelines are followed, there may still be temperature errors, attributed to noise being coupled on to the D1+ and D1− lines. High frequency noise generally has the effect of producing temperature measurements that are consistently too high by a specific amount. The ADT7484A/ ADT87486A have a temperature offset command code of 0xe0 through which a desired offset can be set. By doing a one−time calibration of the system, the offset caused by system board noise can be calculated and nulled by specifying it in the ADT7484A/ADT7486A. The offset is automatically added to every temperature measurement. The maximum offset is ±128°C with 0.25°C resolution. The offset format is the same as the temperature data format; 16−bit, twos complement notation, as shown in Table 8. The offset should be programmed in little endian format, that is, LSB before MSB. The offset value is also returned in little endian format when read. VCC 2N3904 OR CPU THERMAL DIODE ADT7484A 1 VCC SST 8 2 GND ADD0 7 3 D1+ RESERVED 6 4 D1– 5 ADD1 SST Figure 17. ADT7484A Typical Application Schematic VCC 2N3904 NPN ADT7486A 1 VCC 2 GND 3 D1+ RESERVED 8 4 D1– ADD1 7 5 D2+ D2– 6 SST 10 ADD0 9 SST CPU THERMAL DIODE Figure 18. ADT7486A Typical Application Schematic ORDERING INFORMATION Device Order Number* ADT7484AARZ-REEL Branding Package Option Package Type Shipping† − R−8 SOIC−8 NB 2500 Tape & Reel ADT7484AARZ-RL7 − R−8 SOIC−8 NB 1000 Tape & Reel ADT7484AARMZ-RL T20 RM−8 8-Lead MSOP 3000 Tape & Reel ADT7484AARMZ-R7 T20 RM−8 8-Lead MSOP 1000 Tape & Reel ADT7486AARMZ-RL T22 RM−10 10-Lead MSOP 3000 Tape & Reel ADT7486AARMZ-R7 T22 RM−10 10-Lead MSOP 1000 Tape & Reel †For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D. *These are Pb−Free packages. http://onsemi.com 11 ADT7484A/ADT7486A PACKAGE DIMENSIONS SOIC−8 NB CASE 751−07 ISSUE AJ −X− NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION A AND B DO NOT INCLUDE MOLD PROTRUSION. 4. MAXIMUM MOLD PROTRUSION 0.15 (0.006) PER SIDE. 5. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.127 (0.005) TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM MATERIAL CONDITION. 6. 751−01 THRU 751−06 ARE OBSOLETE. NEW STANDARD IS 751−07. A 8 5 S B 0.25 (0.010) M Y M 1 4 −Y− K G C N DIM A B C D G H J K M N S X 45 _ SEATING PLANE −Z− 0.10 (0.004) H D 0.25 (0.010) M Z Y S X M J S SOLDERING FOOTPRINT* 1.52 0.060 7.0 0.275 4.0 0.155 0.6 0.024 1.270 0.050 SCALE 6:1 mm Ǔ ǒinches *For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. http://onsemi.com 12 MILLIMETERS MIN MAX 4.80 5.00 3.80 4.00 1.35 1.75 0.33 0.51 1.27 BSC 0.10 0.25 0.19 0.25 0.40 1.27 0_ 8_ 0.25 0.50 5.80 6.20 INCHES MIN MAX 0.189 0.197 0.150 0.157 0.053 0.069 0.013 0.020 0.050 BSC 0.004 0.010 0.007 0.010 0.016 0.050 0 _ 8 _ 0.010 0.020 0.228 0.244 ADT7484A/ADT7486A PACKAGE DIMENSIONS MSOP8 CASE 846AB−01 ISSUE O D HE PIN 1 ID NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION A DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.15 (0.006) PER SIDE. 4. DIMENSION B DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. INTERLEAD FLASH OR PROTRUSION SHALL NOT EXCEED 0.25 (0.010) PER SIDE. 5. 846A-01 OBSOLETE, NEW STANDARD 846A-02. E e b 8 PL 0.08 (0.003) M T B S A S SEATING −T− PLANE 0.038 (0.0015) A A1 MILLIMETERS NOM MAX −− 1.10 0.08 0.15 0.33 0.40 0.18 0.23 3.00 3.10 3.00 3.10 0.65 BSC 0.40 0.55 0.70 4.75 4.90 5.05 DIM A A1 b c D E e L HE MIN −− 0.05 0.25 0.13 2.90 2.90 L c SOLDERING FOOTPRINT* 8X 1.04 0.041 0.38 0.015 3.20 0.126 6X 8X 4.24 0.167 0.65 0.0256 5.28 0.208 SCALE 8:1 mm Ǔ ǒinches *For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. http://onsemi.com 13 INCHES NOM −− 0.003 0.013 0.007 0.118 0.118 0.026 BSC 0.021 0.016 0.187 0.193 MIN −− 0.002 0.010 0.005 0.114 0.114 MAX 0.043 0.006 0.016 0.009 0.122 0.122 0.028 0.199 ADT7484A/ADT7486A PACKAGE DIMENSIONS MSOP10 CASE 846AC−01 ISSUE O NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSION “A” DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.15 (0.006) PER SIDE. 4. DIMENSION “B” DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. INTERLEAD FLASH OR PROTRUSION SHALL NOT EXCEED 0.25 (0.010) PER SIDE. 5. 846B−01 OBSOLETE. NEW STANDARD 846B−02 −A− −B− K D 8 PL 0.08 (0.003) PIN 1 ID G 0.038 (0.0015) −T− SEATING PLANE M T B S A S C H L J MILLIMETERS MIN MAX 2.90 3.10 2.90 3.10 0.95 1.10 0.20 0.30 0.50 BSC 0.05 0.15 0.10 0.21 4.75 5.05 0.40 0.70 DIM A B C D G H J K L INCHES MIN MAX 0.114 0.122 0.114 0.122 0.037 0.043 0.008 0.012 0.020 BSC 0.002 0.006 0.004 0.008 0.187 0.199 0.016 0.028 SOLDERING FOOTPRINT* 10X 1.04 0.041 0.32 0.0126 3.20 0.126 8X 10X 4.24 0.167 0.50 0.0196 SCALE 8:1 5.28 0.208 mm Ǔ ǒinches *For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. 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