View ADT7401_749118.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

SMBus/I2C(R) Compatible, 0.5C Accurate 12-Bit Digital Temperature Sensor with Daisy Chain
Preliminary Technical Data
FEATURES
12-Bit Temperature-to-Digital Converter 0.5C Accuracy at 25C 1C Accuracy from 0C to +70C Operation from -40C to 150C Operation from 2.7V to 5.5V Power Consumption TBD mW Max at 5.5 V Power Saving One Shot Mode Pin Selectable Addressing via AS pin Sub-SMBus/I2C Bus via DC pin Small Low Cost 6-Pin SOT-23 Package and 8-Pin MSOP
ADT7401
The ADT7401 is specified for operation at supply voltages from 2.7 V to 5.5 V. Operating at 3.3 V the supply current is typically 230 A. The ADT7401 is rated for operation over the -40C to +150C temperature range. It is packaged in a low cost, low area SOT-23 package and mini-SOIC package. The SMBus ALERT pin is an open-drain output that is used as an out of limit temperature indicator. It can be wired-AND with other SMBus ALERT pins and is used in conjunction with the SMBus General Call Address. The DC (Daisy Chain) pin creates a sub-SMBus/I2C bus where a multiple of ADT7401's can be used. The DC pin has the advantage of freeing up the address options on the root bus as only one ADT7401 root address needs to be used by the SMBus/I2C controller but still being able to address a number of ADT7401 temperature sensors.
APPLICATIONS
Isolated Sensors Environmental Control Systems Refrigeration Systems Thermal Protection Industrial Process Control Power System Monitors Automotive Medical
PRODUCT HIGHLIGHTS
1. The ADT7401 has an on-chip temperature sensor that allows an accurate measurement of the ambient temperature. The measurable temperature range is -40C to +150C. Supply voltage of 2.7 V to 5.5 V. Space-saving 6-lead SOT-23 package and 8-lead MSOP. Temperature accuracy of 0.5C. 0.0625C temperature resolution. The ADT7401 features a one shot mode that reduces the power consumption to 2.57 W at one sample per second.
GENERAL DESCRIPTION
The ADT7401 is a complete temperature monitoring system that outputs a 12-bit digital word corresponding to the temperature of the ADT7401's silicon. The device offers a high temperature accuracy of 1C from 0C to +70C, with excellent transducer linearity. The digital output of the ADT7401 is SMBus/I2C compatible.
2. 3. 4. 5. 6.
FUNCTIONAL BLOCK DIAGRAM
Figure 1. SOT-23 Functional Block Diagram Rev. PrE
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 (c) 2004 Analog Devices, Inc. All rights reserved.
ADT7401 TABLE OF CONTENTS
Specifications..................................................................................... 3 Timing Characteristics..................................................................... 4 Absolute Maximum Ratings............................................................ 5 ESD Caution.................................................................................. 5 Pin Configuration and Function Descriptions............................. 6 Typical Performance Curves ........................................................... 7 Circuit Information...................................................................... 9 Converter Details.......................................................................... 9
Preliminary Technical Data
Application Hints ........................................................................... 10 Thermal Response Time ........................................................... 10 Self-Heating Effects.................................................................... 10 Supply Decoupling ..................................................................... 10 Temperature Monitoring........................................................... 10 Outline Dimensions ....................................................................... 11 Ordering Guide .......................................................................... 12
Rev. PrE | Page 2 of 12
Preliminary Technical Data SPECIFICATIONS
ADT7401
All specifications apply for -40C to +150C unless otherwise stated. TA = TMIN to TMAX, VDD = +2.7 V to +5.5 V, unless otherwise noted Table 1.
Parameter TEMPERATURE SENSOR AND ADC Accuracy @ VDD= +3.3 V (10%) Min Typ Max 0.5 1 2 3 41 0.5 1 2 3 41 0.0625 200 1 0.25 0.3 Units C C C C C C C C C C C ms s C C/V A V V pF ns V V mA pF V A A A A A A A W W W Serial Bus Inactive. Device Converting. Device Converting. Device not converting. Device not converting. Average Current @ VDD= 2.7 V to 3.6 V. Average Current @ VDD= 4.5 V to 5.5 V. VDD= +3.3 V, Continuously Converting Average Power Dissipated for VDD= +3.3 V. One Shot Mode. Average Power Dissipated for VDD= +5 V. One Shot Mode. Test Conditions/Comments TA= 25C. TA= 0C to 70C. TA= -40C to +85C. TA= -40C to +125C. TA= -40C to +150C. TA= 25C. TA= 0C to 70C. TA= -40C to +85C. TA= -40C to +125C. TA= -40C to +150C. Equivalent to 12 Bits Sigma Delta ADC Time between each conversion Drift over 10 years if part is operated at +55C. TA= +25C VIN= 0 V to VDD
Accuracy @ VDD= +5 V (10%)
Temperature Resolution Temperature Conversion Time Temperature Update Rtae Long Term Drift Power Supply Rejection Ratio DIGITAL INPUTS2 Input Current VIL, Input Low Voltage VIH, Input High Voltage Pin Capacitance SCL, SDA Glitch Rejection DIGITAL OUTPUTS2 VOH, Ouput High Voltage VOL, Output Low Voltage IOH, Output High Current COUT, Output Capacitance SUPPLIES Supply Voltage Supply Current Normal Mode6@ 3.3 V Normal Mode6@ 5 V Quiescent6@ 3.3 V Quiescent6@ 5.5 V One Shot Mode @ 1 sps One Shot Mode @ 1 sps Shutdown Current Power Dissipation Power Dissipation 1 sps 1 sps
0.6 1 0.3xVDD
0.7xVDD 3 10 50
All digital inputs Input filtering suppresses noise spikes of less than 50 ns. ISOURCE= ISINK= 200 A IOL= 3 mA VOH= 5 V
2.4 0.4 1 50 2.7 230 300 3 5 21.16 28.6 0.3 759 69.83 143 5.5 450 500 8 10
1
1
2
It is not recommended to operate the device at temperatures above +125C for greater than a total of 5% of the lifetime of the device. Any exposure beyond this limit will affect device reliability. Guaranteed by design and characterization, not production tested.
Rev. PrE | Page 3 of 12
ADT7401 TIMING CHARACTERISTICS
Preliminary Technical Data
Guaranteed by design and characterization, not production tested. The SDA & SCL timing is measured with the input filters turned on so as to meet the Fast-Mode I2C specification. Switching off the input filters improves the transfer rate but has a negative affect on the EMC behaviour of the part. TA = TMIN to TMAX, VDD = +2.7 V to +5.5 V, unless otherwise noted. Table 2.
Parameter Serial Clock Period, t1 Data In Setup Time to SCL High, t2 Data Out Stable after SCL Low, t3 SDA Low Setup Time to SCL Low (Start Condition), t4 SDA High Hold Time after SCL High (Stop Condition), t5 SDA and SCL Fall Time, t6 Limit 2.5 50 0 50 50 90 Units s ns ns ns ns ns Comments Fast Mode I2C. See Figure 2 See Figure 2 See Figure 2 See Figure 2 See Figure 2
Figure 2. SMBus/I2C Timing Diagram
Figure 3. Load Circuit for Access Time and Bus Relinquish Time
Rev. PrE | Page 4 of 12
Preliminary Technical Data ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter VDD to GND Digital Input Voltage to GND Maximum Output Current (OUT) Operating Temperature Range3 Storage Temperature Range Max Junction Temperature, TJMAX 6-Lead SOT-23 Power Dissipation4 Thermal Impedance6 JA, Junction-to-Ambient (still air) JC, Junction-to-Case 8-Lead MSOP (RM-8) Power Dissipation2 Thermal Impedance4 JA, Junction-to-Ambient (still air) JC, Junction-to-Case IR Reflow Soldering Peak Temperature Time at Peak Temperature Ramp-up Rate Ramp-down Rate Rating -0.3 V to +7 V -0.3 V to VDD + 0.3 V 10 mA -40C to +150C -65C to +160C +150C WMAX = (TJMAX - TA5)/JA 229.6C/W 91.99C/W WMAX = (TJMAX - TA3)/JA 205.9C/W 43.74C/W +220C (-0/+5C) 10 to 20 secs 2-3C/sec -6C/sec
ADT7401
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Figure 4. Plot of Maximum Power Dissipation vs. Temperature
3
It is not recommended to operate the device at temperatures above +125C for greater than a total of 5% of the lifetime of the device. Any exposure beyond this limit will affect device reliability. 4 Values relate to the package being used on a 2-layer PCB. See Figure 4. for a plot of max power dissipation vs. ambient temperature (TA). 5 TA = Ambient Temperature. 6 Junction-to-Case resistance is applicable to components featuring a preferential flow direction, e.g. components mounted on a heat sink. Junction-to-Ambient resistance is more useful for air-cooled PCB mounted components.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. PrE | Page 5 of 12
ADT7401 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Preliminary Technical Data
Figure 5. Pin Configurations
Table 4. Pin Function Description
Mnemonic SDA SCL ALERT GND DC VDD A0 A1 SOT-23 Pin No. 6 5 4 3 2 1 MSOP Pin No. 1 2 3 4 7 8 5 6 Description SMBus/I2C Serial Data Input/Output. Open-drain configuration needs a pullup resistor. Serial clock input. Open-drain configuration. Digital open-drain output. Out of limit temperature indicator. This output becomes active when temperature exceeds THIGH or TLOW limits. Can be programmed to be active low or active high Analog and Digital Ground. Daisy Chain Digital Input/Output. This pin acts as the input/output conduit for the sub-SMBus/I2C bus. Push-Pull configuration. Positive Supply Voltage, 2.7 V to 5.5 V. Digital Input. User set programmable bit of the serial bus address. Digital Input. User set programmable bit of the serial bus address.
Rev. PrE | Page 6 of 12
Preliminary Technical Data TYPICAL PERFORMANCE CURVES
ADT7401
Figure 6. Supply Current vs. Supply Voltage @ +25C
Figure 8. PSRR vs. Supply Ripple Frequency
Figure 7. Shutdown Current vs. Supply Voltage @ +25C
Figure 9. Temperature Error at 3.3 V and 5 V
Rev. PrE | Page 7 of 12
ADT7401
Preliminary Technical Data
Figure 10. Temperature Error vs. Power Supply Noise Frequency
Figure 12. Supply Current vs. Temperature
Figure 11. Temperature Sensor Response to Thermal Shock
Figure 13. Power Supply Rejection vs. Temperature
Rev. PrE | Page 8 of 12
Preliminary Technical Data
CIRCUIT INFORMATION
The ADT7401 is a standalone temperature sensor that generates a 12-bit digital output in two's complement that varies in direct proportion with the temperature of the device. An onboard sensor generates a voltage precisely proportional to absolute temperature which is compared to an internal voltage reference and input to a precision digital modulator. The serial digital output is converted into a 12-bit digital word and stored in the Temperature Value Register. Overall accuracy is 5C from 0C to +70C, with excellent transducer linearity. The digital output of the ADT7401 is SMBus/I2C compatible, and is easily interfaced to most popular microcontrollers. The onboard temperature sensor has excellent accuracy and linearity over the entire rated temperature range without correction or calibration by the user. The sensor output is digitized by a first-order sigma-delta modulator, also known as the "charge balance" type analog-todigital converter. This type of converter utilizes time-domain oversampling and a high accuracy comparator to deliver 12 bits of effective accuracy in an extremely compact circuit.
ADT7401
cycle of the comparator output in response to input voltage changes. The comparator samples the output of the integrator at a much higher rate than the input sampling frequency, this is called oversampling. This spreads the quantization noise over a much wider band than that of the input signal, improving overall noise performance and increasing accuracy.
Figure 14. First-Order Sigma-Delta Modulator
CONVERTER DETAILS
The sigma-delta modulator consists of an input sampler, a summing network, an integrator, a comparator, and a 1-bit DAC. Similar to the voltage-to-frequency converter, this architecture creates in effect a negative feedback loop whose intent is to minimize the integrator output by changing the duty
The modulated output of the comparator is encoded using a circuit technique, which results in a serial digital signal. This signal is then converted into a 12-bit digital word for storage into a register. The final output format is two's complement.
Rev. PrE | Page 9 of 12
ADT7401 APPLICATION HINTS
THERMAL RESPONSE TIME
The time required for a temperature sensor to settle to a specified accuracy is a function of the thermal mass of, and the thermal conductivity between, the sensor and the object being sensed. Thermal mass is often considered equivalent to capacitance. Thermal conductivity is commonly specified using the symbol , and can be thought of as thermal resistance. It is commonly specified in units of degrees per watt of power transferred across the thermal joint. Thus, the time required for the ADT7401 to settle to the desired accuracy is dependent on the package, the thermal contact established in that particular application, and the equivalent power of the heat source. In most applications, the settling time is probably best determined empirically. inductance.
Preliminary Technical Data
If possible, the ADT7401 should be powered directly from the system power supply. This arrangement, shown in Figure 15, will isolate the analog section from the logic switching transients. Even if a separate power supply trace is not available, however, generous supply bypassing will reduce supply-line induced errors. Local supply bypassing consisting of a 0.1 F ceramic capacitor is recommended.
SELF-HEATING EFFECTS
The temperature measurement accuracy of the ADT7401 may be degraded in some applications due to self-heating. Errors introduced are from the quiescent dissipation and power dissipated when converting. The magnitude of these temperature errors is dependent on the thermal conductivity of the ADT7401 package, the mounting technique, and effects of airflow. Static dissipation in the ADT7401 is typically 10 W operating at 3.3 V with no load. In the 6 lead SOT-23 package mounted in free air, this accounts for a temperature increase due to self-heating of:
Figure 15. Use Separate Traces to Reduce Power Supply Noise
TEMPERATURE MONITORING
The ADT7401 is ideal for monitoring the thermal environment within electronic equipment. For example, the surface mounted package will accurately reflect the exact thermal conditions which affect nearby integrated circuits. The ADT7401 measures and converts the temperature at the surface of their own semiconductor chip. When the ADT7401 is used to measure the temperature of a nearby heat source, the thermal impedance between the heat source and the ADT7401 must be considered. Often, a thermocouple or other temperature sensor is used to measure the temperature of the source while the ADT7401's temperature is monitored. Once the thermal impedance is determined, the temperature of the heat source can be inferred from the ADT7401 output. One example of using the ADT7401's unique properties is in monitoring a high power dissipation microprocessor. The ADT7401, in a surface mount package, is mounted directly beneath the microprocessor's pin grid array (PGA) package.
T = PDISS x JA = 143W x 229.6C / W = 0.0328C
It is recommended that current dissipated through the device is kept to a minimum as it has a proportional affect on the temperature error.
SUPPLY DECOUPLING
The ADT7401 should be decoupled with a 0.1 F ceramic capacitor between VDD and GND. This is particularly important if the ADT7401 is mounted remote from the power supply. Precision analog products, such as the ADT7401, require a well filtered power source. Since the ADT7401 operates from a single supply, it seems convenient to simply tap into the digital logic power supply. Unfortunately, the logic supply is often a switch-mode design, which generates noise in the 20 kHz to 1 MHz range. In addition, fast logic gates can generate glitches hundred of millivolts in amplitude due to wiring resistance and
Rev. PrE | Page 10 of 12
Preliminary Technical Data OUTLINE DIMENSIONS
ADT7401
Figure 16. 6-Lead Plastic Surface Mount SOT-23 RT-6) Dimensions shown in Millimeters
Figure 17. 8-Lead Plastic Surface Mount Mini/Micro SOIC (MSOP) (RM-8) Dimensions shown in Millimeters
Rev. PrE | Page 11 of 12
ADT7401
ORDERING GUIDE
Model ADT7401RT500REEL7 ADT7401RT-REEL ADT7401RTREEL7 ADT7401RM500REEL7 ADT7401RMREEL ADT7401RMREEL7 Temperature Range1 -40C to +150C -40C to +150C -40C to +150C -40C to +150C -40C to +150C -40C to +150C Temperature Accuracy2 1C 1C 1C 1C 1C 1C Package Description 6-Lead SOT-23 6-Lead SOT-23 6-Lead SOT-23 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP Branding Information
Preliminary Technical Data
Package Option RJ-6 RJ-6 RJ-6 RM-8 RM-8 RM-8
Minimum Quantities/Reel 500 10000 3000 500 10000 3000
Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips.
1
It is not recommended to operate the device at temperatures above +125C for greater than a total of 5% of the lifetime of the device. Any exposure beyond this limit will affect device reliability. 2 Temperature accuracy is over 0C to +70C temperature range.
(c) 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective companies. PR04792-0-3/04(PrE)
Rev. PrE | Page 12 of 12

▲Up To Search▲

Price & Availability of ADT7401

	To Download ADT7401 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .