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LTM2985

Analog Devices

Isolated High Accuracy Digital Temperature Measurement System with EEPROM

Manufacturer: Analog Devices

Document: 90 Pages / 3Mb

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LTC2985 (Rev. 0)

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Manufacturer or author: Analog Devices Inc.
PDF pages: 90

Technical content

Rev. AFor more information www.analog.comDocument Feedback TYPICAL APPLICATION FEATURES DESCRIPTION Isolated High Accuracy Digital Temperature Measurement System with EEPROM The LT M 2985 measures a wide variety of temperature sensors and digitally outputs the result, in °C or °F , with 0.1°C accuracy and 0.001°C resolution. The LTM2985 can measure the temperature of virtually all standard (Type B, E, J, K, N, S, R, T) or custom thermocouples, automatically compensate for cold junction temperatures and linearize the results. The device can also measure temperature with standard 2-, 3- or 4-wire RTDs, thermistors and diodes. The LTM2985 includes excitation current sources and fault detection circuitry appropriate for each type of temperature sensor . The LTM2985 is an isolated 10-channel temperature mea- surement system software compatible with the LTC2986-1. It provides 5kV isolated power and SPI interface to the precision temperature-to-bits converter . The LTM2985 also includes a user-programmable EEPROM for custom sensor data. Universal Isolated Temperature Measurement System Typical Temperature Error Contribution

APPLICATIONS

All registered trademarks and trademarks are the property of their respective owners. Patents Pending n 5000VRMS Isolated Power and SPI Interface n Directly Digitizes 2-, 3- or 4-Wire RTDs, Thermocouples, Thermistors and Diodes n 10 Flexible Inputs Allow Interchanging Sensors n Automatic Thermocouple Cold Junction Compensation n Built-In Standard and User-Programmable Coefficients for Thermocouples, RTDs and Thermistors n Automatic Burn Out, Short-Circuit and Fault Detection n Buffered Inputs Allow External Protection n Simultaneous 50Hz/60Hz Rejection n Includes 15ppm/°C (Max) Reference n Includes Special Protection Modes n On-Chip EEPROM Stores Channel Configuration Data and Custom Coefficients n Direct Thermocouple Measurements n Direct RTD Measurements n Direct Thermistor Measurements n Custom Sensor Applications TEMPERATURE (°C) –200 –0.5 ERROR (°C) 0.3 0.2 0.1 –0.1 –0.2 –0.3 –0.4 0.5 200 600 800

2985 TA01b

0.4 0 400 1000 14001200 THERMISTOR THERMOCOUPLE RTD

3904 DIODE

29861 TA02

4.5V TO 5.5V L TM2985 GND2 VCC VL ON GND RP6

2985 TA01a

Rev. A For more information www.analog.com TABLE OF CONTENTS

Rev. AFor more information www.analog.com PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS Logic Inputs: Logic Outputs: Analog Input Pins (CH1 to CH10, COM) (Notes 1) ORDER INFORMATION BGA PACKAGE 66-LEAD (22mm × 15mm × 3.66mm) TJMAX = 105°C, θJA = 31.7°C/W , θJC(top) = 16°C/W , θJC(bottom) = 19.7°C/W , NOTE: 1) θ VALUES ARE DETERMINED BY SIMULATION PER JESD51 CONDITIONS; 2) θJA VALUE IS OBTAINED WITH DEMO BOARD TOP VIEW T R S A B C 21 43 5 6 7 9 10 118 SDODNC SDISCK CS SDOE ON GND VCC VL DOUT GND DNC CH4GND2 CH3 CH2 CH1 DNC GND2 VCC2GND2 CH5 COM GND2 CH10 DNC VREFGND2 INTGND2 CH6DIN CH7 CH8 CH9 DNC PART NUMBER PAD OR BALL FINISH PART MARKING PACKAGE TYPE MSL RATING TEMPERATURE RANGE DEVICE FINISH CODE LTM2985CY#PBF SAC305 (RoHS) LTM2985Y e1 BGA 4 0°C to 70°C LTM2985IY#PBF –40°C to 85°C

Device temperature grade is indicated by a label on the shipping container .
Pad or ball finish code is per IPC/JEDEC J-STD-609.
Recommended BGA PCB Assembly and Manufacturing Procedures.
BGA Package and Tray Drawings

Rev. A For more information www.analog.com COMPLETE SYSTEM ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VL = 3.3V and GND = GND2 = 0V, ON = VL unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Input Supplies VCC Input Supply Range l 4.5 5 5.5 V VL Logic Supply Range l 1.62 5.5 V ICC Input Supply Current ON = VL , No Load l 80 mA IL Logic Supply Current ON = 0V ON = VL l 10 μA μA Output Supplies VCC2 Regulated Output Voltage Output Voltage Operating Range Line Regulation Load Regulation No Load (Note 3) External ILOAD = 1mA, MIN ≤ VCC ≤ MAX External ILOAD = 100μA to 1mA l l l 4.75 5.25 5.5 100 V V mV mV ICC2 Output Short Circuit Current VCC2 = 0V 150 mA Current Limit ∆VCC2 ≤ –5% l 1 mA Logic VITH Input Threshold Voltage ON, SDOE, SCK, SDI, CS 1.62V ≤ VL < 2.35V ON, SDOE, SCK, SDI, CS 2.35V ≤ VL ≤ 5.5V DIN l l l 0.25 • VL 0.33 • VL 0.33 • VCC2 0.75 • VL 0.67 • VL 0.67 • VCC2 V V V IIN Input Current ON, SDOE, SCK, SDI, CS, DIN, VL = 5V, VIN = 0V, 5V l ±1 μA VHYS Input Hysteresis (Note 3) 150 mV VOH Output High Voltage DOUT , SDO ILOAD = –1mA, 1.62V ≤ VL < 3V ILOAD = –4mA, 3V ≤ VL ≤ 5.5V l VL – 0.4 V VOL Output Low Voltage DOUT , SDO ILOAD = 1mA, 1.62V ≤ VL < 3V ILOAD = 4mA, 3V ≤ VL ≤ 5.5V l 0.4 V ISC Short-Circuit Current 0V ≤ (DOUT , SDO) ≤ VL l ±85 mA

Rev. AFor more information www.analog.com PARAMETER CONDITIONS MIN TYP MAX UNITS Resolution (No Missing Codes) –FS ≤ VIN ≤ +FS 24 Bits Integral Nonlinearity VIN(CM) = 1.25 (Note 14) l 2 30 ppm of VREF Offset Error l 0.5 2 μV Offset Error Drift (Note 3) l 10 20 nV/ºC Positive Full-Scale Error (Notes 2, 14) l 100 ppm of VREF Positive Full-Scale Drift (Notes 2, 14) l 0.1 ppm of VREF/ºC Input Leakage I-Grade, C-Grade (Note 18) l 1 nA Negative Full-Scale Error (Notes 2, 14) l 100 ppm of VREF Negative Full-Scale Drift (Notes 2, 14) l 0.1 ppm of VREF/ºC Input Referred Noise I-Grade, C-Grade (Note 4) l 0.8 1.5 µVRMS Common Mode Input Range l –0.05 VCC2 – 0.3 V RTD Excitation Current (Note 15) l –25 Table 33 25 % RTD Excitation Current Matching Continuously Calibrated l Error within Noise Level of ADC V Thermistor Excitation Current (Note 15) l –37.5 Table 57 37.5 % Input Range All Analog Input Channels l –0.05 VCC2 – 0.3 V Output Rate T wo Conversion Cycle Mode (Notes 5, 8) l 150 164 170 ms Three Conversion Cycle Mode (Notes 5, 8) l 225 246 255 ms Input Common Mode Rejection 50Hz/60Hz (Note 3) l 120 dB Input Normal Mode Rejection 60Hz (Notes 3, 6) l 120 dB 50Hz (Notes 3, 7) l 120 dB 50Hz/60Hz (Notes 3, 5, 8) l 75 dB Analog Power-Up (Note 10) l 100 ms Digital Initialization (Note 11) l 100 ms REFERENCE ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS MIN TYP MAX UNITS Output Voltage VREF (Note 9) 2.49 2.51 V Output Voltage Temperature Coefficient I-Grade l 3 15 ppm/ºC C-Grade l 3 20 ppm/ºC Load Regulation IOUT(SOURCE) = 100µA IOUT(SINK) = 100µA l l mV/mA mV/mA Output Voltage Noise 0.1Hz ≤ f ≤ 10Hz 10Hz ≤ f ≤ 1kHz 4.5 μVP-P μVP-P Output Short Circuit Current Short VREF to GND Short VREF to VCC2 mA mA Long Term Drift of Output Voltage (Notes 3, 12) 60 ppm/√kHr Hysteresis ∆T = 0ºC to 70ºC (Note 13) ∆T = –40ºC to 85ºC (Note 13) ppm ppm ADC ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.

Rev. A For more information www.analog.com DIGITAL INPUTS AND DIGITAL OUTPUTS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS External SCK Frequency Range l 0 1.5 MHz External SCK LOW Period l 350 ns External SCK HIGH Period l 350 ns SDOE￬ to SDO Valid￬￬ RLOAD = 1kΩ, CLOAD = 15pF l 0 400 ns SDOE￬ to SDO Hi-Z (Note 3) RLOAD = 1kΩ, CLOAD = 15pF l 0 200 ns t1 CS￬ to SCK￬ l 200 ns t2 SCK￬ to SDO Valid l 425 ns t3 SDO Hold After SCK￬ l 10 ns t4 SDI Setup Before SCK￬ l 100 ns t5 SDI Hold After SCK￬ l 200 ns tR Rise Time CLOAD = 15pF l 3 12.5 ns tF Fall Time CLOAD = 15pF l 3 12.5 ns PARAMETER CONDITIONS MIN TYP MAX UNITS Rated Dielectric Insulation Voltage 1 Minute, Derived from 1 Second Test (Notes 20, 21) 5000 VRMS Rated Dielectric Insulation Voltage 1 Second (Note 3) 6000 VRMS Common Mode T ransient Immunity VL = ON = 3.3V, VCM = 1kV, ∆t = 33ns 30 50 kV/µs Maximum Continuous Working Voltage (Note 3) 1000 VPEAK Maximum Continuous Working Voltage (Note 3) 690 VRMS Partial Discharge VPD = 1300VPEAK 5 pC Comparative T racking Index IEC 60112 (Note 3) 600 VRMS Depth of Erosion IEC 60112 (Note 3) 0.017 mm Distance Through Insulation (Note 3) 0.2 mm Input to Output Resistance (Note 3) 1 5 TΩ Input to Output Capacitance (Note 3) 5 pF Creepage Distance (Note 3) 14.49 mm ISOLATION CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.

Rev. AFor more information www.analog.com Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: Full scale ADC error . Measurements do not include reference error . Note 3: Guaranteed by design, not subject to test. Note 4: The input referred noise includes the contribution of internal calibration operations. Note 5: MUX configuration delay = default 1ms. Note 6: Global configuration set to 60Hz rejection. Note 7: Global configuration set to 50Hz rejection. Note 8: Global configuration default 50Hz/60Hz rejection. Note 9: The exact value of VREF is stored in the LTM2985 and used for all measurement calculations. Temperature coefficient is measured by dividing the maximum change in output voltage by the specified temperature range. Note 10: Analog power-up. Command status register inaccessible during this time. Note 11: Digital initialization. Begins at the conclusion of analog power-up. Command status register is 0×80 at the beginning of digital initialization and 0×40 at the conclusion. Note 12: Long-term stability typically has a logarithmic characteristic and therefore, changes after 1000 hours tend to be much smaller than before that time. Total drift in the second thousand hours is normally less than one third that of the first thousand hours with a continuing trend toward reduced drift with time. Long-term stability will also be affected by differential stresses between the IC and the board material created during board assembly. Note 13: Hysteresis in output voltage is created by package stress that differs depending on whether the IC was previously at a higher or lower temperature. Output voltage is always measured at 25°C, but the IC is cycled to the hot or cold temperature limit before successive measurements. Hysteresis measures the maximum output change for the averages of three hot or cold temperature cycles. For instruments that are stored at well controlled temperatures (within 20 or 30 degrees of operational temperature), it is usually not a dominant error source. Typical hysteresis is the worst-case of 25°C to cold to 25°C or 25°C to hot to 25°C, preconditioned by one thermal cycle. Note 14: Differential Input Range is ±VREF/2. Note 15: RTD and thermistor measurements are made ratiometrically. As a result, current source excitation variation does not affect absolute accuracy. Choose an excitation current such that largest sensor or RSENSE resistance value, when driven by the nominal excitation current, will drop 1V or less. The extended ADC input range will accommodate variation in excitation current and the ratiometric calculation will negate the absolute value of the excitation current. Note 16: 10-year data retention guaranteed for up to 1000 program cycles. Note 17: Do not apply voltage or current sources to these pins. They must be connected to capacitive loads only. Otherwise, permanent damage may occur . Note 18: Input leakage measured with VIN = –10mV and VIN = 2.5V. Note 19: This Module includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125°C when overtemperature protection is active. Continuous operation above specified maximum operating junction temperature may result in device degradation or failure. Note 20: Device considered a 2-terminal device. Pin group A1 through C11 shorted together and pin group R1 through T11 shorted together . Note 21: The rated dielectric insulation voltage should not be interpreted as a continuous voltage rating. LTM2985 EEPROM CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS MIN TYP MAX UNITS Retention (Notes 3, 16) l 10 Years Endurance (Note 3) l 10000 Cycles Programming Time Complete T ransfer from RAM to EEPROM l 2600 ms Read Time Complete T ransfer from EEPROM to RAM l 20 ms

Rev. A For more information www.analog.com Type E Thermocouple Error and RMS Noise vs Temperature Type B Thermocouple Error and RMS Noise vs Temperature RTD PT-1000 Error and RMS Noise vs Temperature Type R Thermocouple Error and RMS Noise vs Temperature Type S Thermocouple Error and RMS Noise vs Temperature Type T Thermocouple Error and RMS Noise vs Temperature TYPICAL PERFORMANCE CHARACTERISTICS Type J Thermocouple Error and RMS Noise vs Temperature Type K Thermocouple Error and RMS Noise vs Temperature Type N Thermocouple Error and RMS Noise vs Temperature THERMOCOUPLE TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G01

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –400 800 1200 16004000 RMS NOISE ERROR THERMOCOUPLE TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G02

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –400 800 1200 16004000 RMS NOISE ERROR THERMOCOUPLE TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G03

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –400 800 1200 16004000 RMS NOISE ERROR THERMOCOUPLE TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G04

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –400 800 1200 1600 20004000 RMS NOISE ERROR THERMOCOUPLE TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G05

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –400 800 1200 1600 20004000 RMS NOISE ERROR THERMOCOUPLE TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G06

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –400 200 400 6000–200 RMS NOISE ERROR THERMOCOUPLE TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G07

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –400 400 800 12000 RMS NOISE ERROR THERMOCOUPLE TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G08

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 400 1200 1600 2000800 RMS NOISE ERROR RTD TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G09

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –400 400 8000 RMS NOISE ERROR T

Rev. AFor more information www.analog.com TYPICAL PERFORMANCE CHARACTERISTICS RTD PT-200 Error and RMS Noise vs Temperature RTD PT-100 Error and RMS Noise vs Temperature RTD NI-120 RTD Error and RMS Noise vs Temperature RTD TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G10

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –400 400 8000 RMS NOISE ERROR RTD TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G11

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –400 0 200 400 600 800 1000–200 RMS NOISE ERROR RTD TEMPERATURE (°C) ERROR/RMS NOISE (°C)

2985 G12

1.0 0.8 0.6 0.4 0.2 –0.2 –0.4 –0.6 –0.8 –1.0 –100 0 100 200 300 RMS NOISE ERROR 5k Thermistor Error vs Temperature 10k Thermistor Error vs Temperature 3k Thermistor Error vs Temperature 30k Thermistor Error vs Temperature YSI-400 Thermistor Error vs Temperature THERMISTOR TEMPERATURE (°C) ERROR (°C)