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FEATURES PRTD Temperature Measurement Range Typical IC Measurement Error ؎ 1؇C Includes Two Matched Current Sources Rail-to-Rail Output Instrumentation Amp Uncommitted, Rail-to-Rail Output Op Amp On-Board ؉ 2.5 V Reference Temperature Coefficient ؎ 25 ppm/؇C ؉ 5 V or ؎ 5 V Operation Supply Current 4 mA Max 10 A Max in Shutdown APPLICATIONS Temperature Controllers Portable Instrumentation Temperature Acquisition Cards GENERAL DESCRIPTION
PRTD Conditioning Circuit and Temperature Controller ADT70*
FUNCTIONAL BLOCK DIAGRAM
NULLA NULLB BIAS 2.5VREFOUT
ADT70
+VS OUTOA
IOUTA IOUTB
MATCHED CURRENT SOURCES 2.5V REF
+INOA ؊INOA
+INIA ؊INIA
INST AMP
SHUTDOWN
SHUTDOWN
RGA RGB GND SENSE
OUTIA AGND ؊VS
DGND
The ADT70 provides excitation and signal conditioning for resistance-temperature devices (RTDs). It is ideally suited for 1 kΩ Platinum RTDs (PRTDs), allowing a very wide range of temperature measurement. It can also easily interface to 100 Ω PRTDs. Using a remote, low cost thin-film PRTD, the ADT70 can measure temperature in the range of –50°C to +500°C. With high performance platinum elements, the temperature change can be extended to 1000°C. Accuracy of the ADT70 and PRTD system over a –200°C to +1000°C temperature range heavily depends on the quality of the PRTD. Typically the ADT70 will introduce an error of only ± 1°C over the transducer's temperature range, and the error may be trimmed to zero at a single calibration point. The ADT70 consists of two matched 1 mA (nominal) current sources for transducer and reference resistor excitation, a precision rail-to-rail output instrumentation amplifier, a 2.5 V reference and an uncommitted rail-to-rail output op amp. The ADT70 includes a shutdown function for battery powered equipment, which reduces the quiescent current from 4 mA to less than 10␣ µA. The ADT70 operates from either single +5 V or ± 5 V supplies. Gain or full-scale range for the PRTD and ADT70 system is set by a precision external resistor connected to the instrumentation amplifier. The uncommitted op amp may be used for scaling the internal voltage reference, providing a “PRTD open” signal or “over-temperature” warning, a heater switching signal, or other external conditioning determined by the user. The ADT70 is specified for operation from ؊40°C to ؉125°C and is available in 20-lead DIP and SO packages. *Patent pending. REV. 0
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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
PIN CONFIGURATIONS 20-Lead P-DIP (N Suffix)
–VS 1 AGND 2 VREFOUT 3 BIAS 4 NULLA 5 20 +VS 19 VOUT OA 18 –INOA 17 +INOA
ADT70
TOP VIEW NULLB 6 (Not to Scale) 15 DGND IOUTA 7 IOUTB 8 –INIA 9 +INIA 10
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16 SHUTDOWN
14 VOUT IA 13 GND SENSE 12 RGB 11 RGA
20-Lead SOIC (R Suffix)
–VS 1 AGND 2 VREFOUT 3 BIAS 4 NULLA 5 20 +VS 19 VOUT OA 18 –INOA 17 +INOA
ADT70
16 SHUTDOWN
TOP VIEW NULLB 6 (Not to Scale) 15 DGND IOUTA 7 IOUTB 8 ؊ INIA 9 ؉ INIA 10
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14 VOUT IA 13 GND SENSE 12 RGB 11 RGA
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 1998
ADT70–SPECIFICATIONS (V = ؉5 V, ؊40؇C ≤ T ≤ ؉125؇C unless otherwise noted)
S
A
Parameter
SYSTEM CONFIGURATION Gain Line Regulation CURRENT SOURCES Output Current Output Current Mismatch Voltage Compliance INSTRUMENTATION AMP Input Offset Voltage Output Offset Voltage Input Bias Current Input Offset Current Common-Mode Rejection Output Voltage Swing Power Supply Rejection Ratio VOLTAGE REFERENCE Output Voltage Load Regulation Temperature Coefficient Line Regulation OPERATIONAL AMPLIFIER Input Offset Voltage Input Offset Voltage Drift Input Bias Current Input Offset Current Open-Loop Voltage Gain Output Voltage Swing Common-Mode Rejection Ratio Power Supply Rejection Ratio Slew Rate SHUTDOWN INPUT Input Low Voltage Input High Voltage POWER SUPPLY Supply Current Shutdown Supply Current Supply Voltage Dual Supply Voltage
Specifications subject to change without notice.
Symbol
Conditions
RL = 1 kΩ
Min
1.234 –2.25
Typ
1.295 Ϯ0.35 0.9 Ϯ0.5 –V S to +VS – 1.5 Ϯ150 Ϯ100 Ϯ5 Ϯ3 Ϯ40 Ϯ30 Ϯ1 85 Ϯ0.5 2.5 2.5 250 Ϯ10 Ϯ75 Ϯ400 Ϯ200 1 Ϯ40 Ϯ30 Ϯ1 2 105 110 150 0.17
Max
1.364 2.25
Units
mV/ Ω %/V mA µA V µV µV mV mV nA nA nA dB mV mV/V V V ppm/mA ppm/ °C ppm/V µV µV µV/°C nA nA nA V/µV mV dB dB dB V/µs
I Q1, IQ2 I Q1 – IQ2
RL = 1 kΩ RL = 1 kΩ
–2
2
VIOS VOOS IB I OS CMR VOUT PSRR
TA = +25°C TA = +25°C TA = +25°C VCM = 0.5 V to 3 V RL = ∞ , VS = Ϯ5 V + 4.5 V ≤ VS ≤ Ϯ 5.5 V
–700 –500 –12 –7 –75 –60 –3 65 –V S + 25 –2.5 2.485 2.49
700 500 12 7 75 60 3 +V S – 25 2.5 2.515 2.51
TA = +25°C I L = 0 mA to 1 mA + 4.5 V ≤ VS ≤ +5.5 V VIOA TCVIOA IB I OS AVOL VOUTA CMRR PSRR .