|
|
PDF ADT70GR Data sheet ( Hoja de datos )
| Número de pieza | ADT70GR | |
| Descripción | PRTD Conditioning Circuit and Temperature Controller | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de ADT70GR (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
|
No Preview Available !
a
PRTD Conditioning Circuit
and Temperature Controller
ADT70*
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
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 preci-
sion rail-to-rail output instrumentation amplifier, a 2.5 V refer-
ence 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.
FUNCTIONAL BLOCK DIAGRAM
NULLA NULLB BIAS 2.5VREFOUT
IOUTA
IOUTB
MATCHED
CURRENT
SOURCES
2.5V
REF
ADT70
+VS
OUTOA
+INOA
؊INOA
+INIA
؊INIA
INST
AMP
SHUT-
DOWN
RGA RGB GND
SENSE
OUTIA AGND ؊VS DGND
PIN CONFIGURATIONS
20-Lead P-DIP
(N Suffix)
–VS 1
20 +VS
AGND 2
19 VOUT OA
VREFOUT 3
18 –INOA
BIAS 4
17 +INOA
NULLA 5 ADT70 16 SHUTDOWN
TOP VIEW
NULLB 6 (Not to Scale) 15 DGND
IOUTA 7
14 VOUT IA
IOUTB 8
13 GND SENSE
–INIA 9
12 RGB
+INIA 10
11 RGA
a
20-Lead SOIC
(R Suffix)
–VS 1
AGND 2
20 +VS
19 VOUT OA
VREFOUT 3
BIAS 4
18 –INOA
17 +INOA
NULLA 5 ADT70 16 SHUTDOWN
TOP VIEW
NULLB 6 (Not to Scale) 15 DGND
IOUTA 7
IOUTB 8
؊ INIA 9
؉ INIA 10
14 VOUT IA
13 GND SENSE
12 RGB
11 RGA
a
SHUTDOWN
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
1 page  
500
400
VS = +5V, NO LOAD
300
200
100
0
؊100
؊200
؊300
؊400
؊500
؊25 25
75 125
TEMPERATURE – ؇C
Figure 7. Instrumentation Amplifier Input Offset Current
vs. Temperature
ADT70
0
؊10 VS = +5V, NO LOAD
؊20
؊30
؊40
؊50
؊60
؊70
؊25
25 75
TEMPERATURE – ؇C
125
Figure 10. Op Amp Input Bias Current vs. Temperature
1.6
VS = +5V, NO LOAD
1.55
1.5
1.45
500
VS = +5V, NO LOAD
400
300
200
100
1.4
؊25
25
75 125
TEMPERATURE – ؇C
Figure 8. Instrumentation Amplifier Gain vs. Temperature
0
؊25
25
75 125
TEMPERATURE – ؇C
Figure 11. Op Amp Input Offset Current vs. Temperature
100
80
VS = +5V, NO LOAD
60
40
20
0
؊20
؊40
؊60
؊80
؊100
؊25
25 75
TEMPERATURE – ؇C
125
Figure 9. Op Amp Input Offset Voltage vs. Temperature
2.51
2.505
VS = +5V, NO LOAD
2.5
2.495
2.49
؊25
25 75
TEMPERATURE – ؇C
125
Figure 12. Reference Voltage vs. Temperature
REV. 0
–5–
5 Page 
ADT70
achieve in a single supply application where the negative rail is
ground or 0 V. Therefore, to achieve full scale operation the
output of ADT70 should be shifted by 1 V to allow for opera-
tion in the 0 V to 5 V region.
The most straightforward method to shift the output voltage
incorporates the use of the GND SENSE as shown in Figure 29.
To shift output voltage range apply a potential equal to the neces-
sary shift on the GND SENSE pin. For example, to shift the out-
put voltage, OUTIA, up to 1 V to GND SENSE, apply 1 V to
GND SENSE. When applying a potential to GND SENSE, care
should be taken to ensure that the voltage source is capable of driv-
ing 2 kΩ and does not introduce excessive noise. Figure 29 uses the
on-board 2.5 V voltage reference for a low noise source. This refer-
ence is then divided to 1 V and buffered by the on-board op amp
to drive GND SENSE at a low impedance. A small 500 Ω potenti-
ometer can be used to calibrate the initial offset error to zero.
However, a voltage applied to GND SENSE is not the only
method to shift the voltage range. Placing a 768 Ω resistor in the
PRTD sensor path also shifts the output voltage by 1 V. This
second method, as shown in Figure 30, is usually not recom-
mended for the following reasons; the input voltage range of the
op amps is limited to around 1 V from the negative and positive
rails and this could cause problems at high temperature, limiting
the upper range to 600°C; the physical location of this resistor
(if placed at a distance from the ADT70) may have an impact
on the noise performance. The method frees up the on-board op
amp for another function and achieves the lowest impedance
ground point for GND SENSE.
This brief section on ADT70 single supply operation has focused
on simple techniques to bias the ADT70 such that all output volt-
ages are within operational range. However, these techniques may
not be useful in all single supply applications. For example, in Fig-
ure 3 the additional on-board op amp is operating at near ground
potential which will create problems in a single supply application
NULLA NULLB BIAS
2.5VREFOUT
IOUTA
IOUTB
1k⍀
REF
RESISTOR
1k⍀
PRTD
SENSOR
؊INIA
RG
49.9k⍀
RG
+INIA
MATCHED
CURRENT
SOURCES
2.5V
REF
INST
AMP
GND
SENSE
OUTIA
ADT70
+VS
OUTOA
+INOA
؊INOA
15k⍀
9.76k⍀
500⍀
POT
SHUT-
DOWN
TO CONTROLLER
SHUTDOWN
DGND
Figure 29. A Single Supply Application with Shifted Ground Sense Pin
+5V
NULLA NULLB BIAS
2.5VREFOUT
ADT70
IOUTA
IOUTB
MATCHED
CURRENT
SOURCES
768⍀
RESISTOR
؊INIA
RG
49.9k⍀
RG
1K⍀
PRTD
1K⍀
+INIA
REF
RESISTOR
INST
AMP
GND
SENSE
2.5V
REF
+VS
OUTOA
+INOA
؊INOA
VREF
SHUT-
DOWN
TO CONTROLLER
SHUTDOWN
؊VS DGND
TO A/D CONVERTER
Figure 30. A Basic Single Supply Operational Diagram with Bias Resistor in Sensor Path
REV. 0
–11–
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet ADT70GR.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| ADT70GN | PRTD Conditioning Circuit and Temperature Controller | Analog Devices |
| ADT70GR | PRTD Conditioning Circuit and Temperature Controller | Analog Devices |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |