AD22100A [ADI]
Voltage Output Temperature Sensor with Signal Conditioning; 电压输出温度传感器与信号调理
| 型号： | AD22100A |
| 厂家： | 
ADI |
| 描述： | Voltage Output Temperature Sensor with Signal Conditioning |
| 文件： | 总6页 (文件大小：233K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Voltage Output Temperature Sensor
with Signal Conditioning
a
AD22100*
FEATURES
SIMPLIFIED BLOCK DIAGRAM
200°C Temperature Span
Accuracy Better than ±2% of Full Scale
Linearity Better than ±1% of Full Scale
Temperature Coefficient of 22.5 mV/°C
Output Proportional to Temperature × V+
Single Supply Operation
V+
Ι
Reverse Voltage Protection
Minimal Self Heating
V
OUT
High Level, Low Impedance Output
R
T
APPLICATIONS
HVAC Systems
System Temperature Compensation
Board Level Temperature Sensing
Electronic Thermostats
MARKETS
Industrial Process Control
Instrumentation
Automotive
GENERAL DESCRIPTION
+5V
The AD22100 is a monolithic temperature sensor with on-chip
signal conditioning. It can be operated over the temperature
range –50°C to +150°C, making it ideal for use in numerous
HVAC, instrumentation and automotive applications.
REFERENCE
ANALOG TO
DIGITAL
CONVERTER
The signal conditioning eliminates the need for any trimming,
buffering or linearization circuitry, greatly simplifying the system
design and reducing the overall system cost.
SIGNAL OUTPUT
DIRECT TO ADC
AD22100
V
O
INPUT
1kΩ
0.1µF
The output voltage is proportional to the temperature times the
supply voltage (ratiometric). The output swings from 0.25 V at
–50°C to +4.75 V at +150°C using a single +5.0 V supply.
–50°C TO +150°C
Due to its ratiometric nature, the AD22100 offers a cost effec-
tive solution when interfacing to an analog-to-digital converter.
This is accomplished by using the ADC’s +5 V power supply as
a reference to both the ADC and the AD22100 (See Figure 1),
eliminating the need for and cost of a precision reference.
Figure 1. Application Circuit
*
Protected by U.S. Patent Nos. 5030849 and 5243319.
REV. B
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.
© Analog Devices, Inc., 1994
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
(T = +25°C and V+ = +4 V to +6 V unless otherwise noted)
AD22100–SPECIFICATIONS
A
AD22100K
Min Typ Max
AD22100A
Min Typ Max
AD22100S
Min Typ Max
Parameter
Units
V
TRANSFER FUNCTION
TEMPERATURE COEFFICIENT
VOUT = (V+/5 V) × [1.375 V + (22.5 mV/°C) × TA]
(V+/5 V) × 22.5
mV/°C
TOTAL ERROR
Initial Error
TA = +25°C
±0.5 ±2.0
±1.0 ±2.0
±1.0 ±2.0
°C
Error over Temperature
TA = TMIN
TA = TMAX
±0.75 ±2.0
±0.75 ±2.0
±2.0 ±3.7
±2.0 ±3.0
±3.0 ±4.0
±3.0 ±4.0
°C
°C
Nonlinearity
TA = TMIN to TMAX
0.5
0.5
1.0
% FS1
OUTPUT CHARACTERISTICS
Nominal Output Voltage
V+ = 5.0 V, TA = 0°C
1.375
3.625
V
V
V
V
V
V
V+ = 5.0 V, TA = +100°C
V+ = 5.0 V, TA = –40°C
V+ = 5.0 V, TA = +85°C
V+ = 5.0 V, TA = –50°C
V+ = 5.0 V, TA = +150°C
0.475
3.288
0.250
4.750
POWER SUPPLY
Operating Voltage
Quiescent Current
+4.0 +5.0 +6.0
+4.0
+5.0 +6.0
500 650
+4.0
+5.0 +6.0
500 650
V
µA
500
650
TEMPERATURE RANGE
Guaranteed Temperature Range
Operating Temperature Range
0
–50
+100
+150
–40
–50
+85
+150
–50
–50
+150
+150
°C
°C
PACKAGE
TO-92
SOIC
TO-92
SOIC
TO-92
SOIC
Specifications subject to change without notice.
(TA = +25°C and V+ = +5.0 V unless otherwise noted)
CHIP SPECIFICATIONS
Parameter
Min
Typ
Max
Units
TRANSFER FUNCTION
TEMPERATURE COEFFICIENT
VOUT = (V+/5 V) × [1.375 + 22.5 mV/°C × TA] V
(V+/5 V) × 22.5
mV/°C
OUTPUT CHARACTERISTICS
Error
TA = +25°C
±0.5
±2.0
°C
Nominal Output Voltage
TA = +25°C
1.938
V
POWER SUPPLY
Operating Voltage
Quiescent Current
+4.0
–50
+5.0
500
+6.0
650
V
µA
TEMPERATURE RANGE
Guaranteed Temperature Range
Operating Temperature Range
25
°C
°C
+150
NOTES
1FS (Full Scale) is defined as that of the operating temperature range, –50°C to +150°C. The listed max specification limit applies to the guaranteed temperature
range. For example, the AD22100K has a nonlinearity of (0.5%) × (200°C) = 1°C over the guaranteed temperature range of 0°C to +100°C.
Specifications subject to change without notice.
–2–
REV. B
AD22100
ABSOLUTE MAXIMUM RATINGS1
PIN DESCRIPTION
Function
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +10 V
Reversed Continuous Supply Voltage . . . . . . . . . . . . . . –10 V
Operating Temperature . . . . . . . . . . . . . . . . –50°C to +150°C
Storage Temperature . . . . . . . . . . . . . . . . . . –65°C to +160°C
Output Short Circuit to V+ or Ground . . . . . . . . . . Indefinite
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . . +300°C
Mnemonic
V+
VO
GND
NC
Power Supply Input
Device Output
Ground Pin must be connected to 0 V.
No Connect
1Stresses above those listed under “Absolute Maximum Ratings” may cause
permanent damage to the device. This is a stress rating only; the functional
operation of the device at these or any other conditions above those indicated in the
operation sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
PIN CONFIGURATIONS
TO-92
BOTTOM VIEW
(Not to Scale)
ORDERING GUIDE
Guaranteed
PIN
2
PIN
1
PIN
3
Temperature
Range
Package
Description* Option
Package
GND
V
V+
Model/Grade
O
AD22100 KT
AD22100 KR
0°C to 100°C
0°C to 100°C
TO-92
SOIC
TO-92
SO-8
AD22100 AT
AD22100 AR
–40°C to +85°C TO-92
–40°C to +85°C SOIC
TO-92
SO-8
SOIC
8
7
6
5
1
2
3
4
V+
NC
AD22100 ST
AD22100 SR
–50°C to +150°C TO-92
–50°C to +150°C SOIC
TO-92
SO-8
V
O
NC
NC
NC
AD22100
TOP VIEW
(Not to Scale)
NC
AD22100KChips +25°C
N/A
N/A
GND
NC = NO CONNECT
*Minimum purchase quantities of 100 pieces for all chip orders.
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 the AD22100 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.
WARNING!
ESD SENSITIVE DEVICE
Typical Performance Curves
250
200
150
100
50
16
14
12
10
8
(SOIC)
T (T0-92)
6
4
2
T (SOIC)
(T0-92)
0
400
800
1200
0
400
800
1200
FLOW RATE – CFM
FLOW RATE – CFM
Figure 3. Thermal Resistance vs. Flow Rate
Figure 2. Thermal Response vs. Flow Rate
REV. B
–3–
AD22100
THEORY OF OPERATION
OUTPUT STAGE CONSIDERATIONS
The AD22100 is a ratiometric temperature sensor IC whose
output voltage is proportional to power supply voltage. The
heart of the sensor is a proprietary temperature-dependent resis-
tor, similar to an RTD, which is built into the IC. Figure 4
shows a simplified block diagram of the AD22100.
As previously stated, the AD22100 is a voltage output device. A
basic understanding of the nature of its output stage is useful for
proper application. Note that at the nominal supply voltage of
5.0 V, the output voltage extends from 0.25 V at –50°C to
+4.75 V at +150°C. Furthermore, the AD22100 output pin is
capable of withstanding an indefinite short circuit to either
ground or the power supply. These characteristics are provided
by the output stage structure shown in Figure 6.
V+
V+
Ι
V
OUT
V
OUT
R
T
Ι
Figure 4. Simplified Block Diagram
Figure 6. Output Stage Structure
The temperature-dependent resistor, labeled RT, exhibits a
change in resistance that is nearly linearly proportional to tem-
perature. This resistor is excited with a current source that is
proportional to power supply voltage. The resulting voltage
across RT is therefore both supply voltage proportional and lin-
early varying with temperature. The remainder of the AD22100
consists of an op amp signal conditioning block that takes the
voltage across RT and applies the proper gain and offset to
achieve the following output voltage function:
The active portion of the output stage is a PNP transistor with
its emitter connected to the V+ supply and collector connected
to the output node. This PNP transistor sources the required
amount of output current. A limited pull-down capability is
provided by a fixed current sink of about –80 µA. (Here,
“fixed” means the current sink is fairly insensitive to either sup-
ply voltage or output loading conditions. The current sink ca-
pability is a function of temperature, increasing its pull-down
capability at lower temperatures.)
VOUT = (V+/5 V) × [1.375 V + (22.5 mV/°C) × TA]
Due to its limited current sinking ability, the AD22100 is inca-
pable of driving loads to the V+ power supply and is instead in-
tended to drive grounded loads. A typical value for short circuit
current limit is 7 mA, so devices can reliably source 1 mA or
2 mA. However, for best output voltage accuracy and minimal
internal self-heating, output current should be kept below 1 mA.
Loads connected to the V+ power supply should be avoided as
the current sinking capability of the AD22100 is fairly limited.
These considerations are typically not a problem when driving
a microcontroller analog to digital converter input pin (see
MICROPROCESSOR A/D INTERFACE ISSUES).
ABSOLUTE ACCURACY AND NONLINEARITY
SPECIFICATIONS
Figure 5 graphically depicts the guaranteed limits of accuracy
for the AD22100 and shows the performance of a typical part.
As the output is very linear, the major sources of error are offset,
i.e., error at room temperature, and span error, i.e., deviation
from the theoretical 22.5 mV/°C. Demanding applications can
achieve improved performance by calibrating these offset and
gain errors so that only the residual nonlinearity remains as a
significant source of error.
RATIOMETRICITY CONSIDERATIONS
4
The AD22100 will operate with slightly better accuracy than
that listed in the data sheet specifications if the power supply is
held constant. This is because the AD22100’s output voltage
varies with both temperature and supply voltage, with some
errors. The ideal transfer function describing the output
voltage is:
3
MAXIMUM ERROR
OVER TEMPERATURE
2
1
0
(V+/5 V) × [1.375 V + (22.5 mV/°C) × TA]
TYPICAL ERROR
–1
The ratiometricity error is defined as the percent change away
from the ideal transfer function as the power supply voltage
changes within the operating range of +4 V to +6 V. For the
AD22100 this error is typically less than 1%. A movement from
the ideal transfer function by 1% at +25°C, with a supply volt-
age varying from 5.0 V to 5.50 V, results in a 1.94 mV change in
output voltage or 0.08°C error. This error term is greater at
higher temperatures because the output (and error term) is di-
rectly proportional to temperature. At 150°C, the error in out-
put voltage is 4.75 mV or 0.19°C.
–2
–3
–4
MAXIMUM ERROR
OVER TEMPERATURE
–50
0
50
TEMPERATURE – °C
100
150
Figure 5. Typical AD22100 Performance
–4–
REV. B
AD22100
Response of the AD22100 output to abrupt changes in ambient
temperature can be modeled by a single time constant τ expo-
nential function. Figure 7 shows typical response time plots for
a few media of interest.
For example, with VS = 5.0 V, and TA = +25°C, the nominal
output of the AD22100 will be 1.9375 V. At VS = 5.50 V, the
nominal output will be 2.1313 V, an increase of 193.75 mV.
A proportionality error of 1% is applied to the 193.75 mV,
yielding an error term of 1.9375 mV. This error term translates
to a variation in output voltage of 2.1293 V to 2.3332 V. A
1.94 mV error at the output is equivalent to about 0.08°C error
in accuracy.
100
ALUMINUM
BLOCK
90
MOVING
80
If we substitute 150°C for 25°C in the above example, then the
error term translates to a variation in output voltage of 5.2203 V
to 5.2298 V. A 4.75 mV error at the output is equivalent to
about 0.19°C error in accuracy.
AIR
70
60
50
40
30
20
10
0
STILL AIR
MOUNTING CONSIDERATIONS
If the AD22100 is thermally attached and properly protected, it
can be used in any measuring situation where the maximum
range of temperatures encountered is between –50°C and
+150°C. Because plastic IC packaging technology is employed,
excessive mechanical stress must be avoided when fastening the
device with a clamp or screw-on heat tab. Thermally conduc-
tive epoxy or glue is recommended for typical mounting condi-
tions. In wet or corrosive environments, an electrically isolated
metal or ceramic well should be used to shield the AD22100.
Because the part has a voltage output (as opposed to current), it
offers modest immunity to leakage errors, such as those caused
by condensation at low temperatures.
0
10
20
30
40
50
60
70
80
90 100
TIME – sec
Figure 7. Response Time
is dependent on θJA and the thermal
capacities of the chip and the package. Table I lists the effec-
tive (time to reach 63.2% of the final value) for a few different
The time constant
τ
τ
media. Copper printed circuit board connections were
neglected in the analysis; however, they will sink or conduct
heat directly through the AD22100’s solder plated copper leads.
When faster response is required, a thermally conductive grease
or glue between the AD22100 and the surface temperature
being measured should be used.
THERMAL ENVIRONMENT EFFECTS
The thermal environment in which the AD22100 is used deter-
mines two performance traits: the effect of self-heating on accu-
racy and the response time of the sensor to rapid changes in
temperature. In the first case, a rise in the IC junction tempera-
ture above the ambient temperature is a function of two vari-
ables; the power consumption of the AD22100 and the thermal
resistance between the chip and the ambient environment θJA.
Self-heating error in °C can be derived by multiplying the power
dissipation by θJA. Because errors of this type can vary widely
for surroundings with different heat sinking capacities, it is nec-
essary to specify θJA under several conditions. Table I shows
how the magnitude of self-heating error varies relative to the en-
vironment. A typical part will dissipate about 2.2 mW at room
temperature with a 5 V supply and negligible output loading. In
still air, without a “heat sink,” the table below indicates a θJA of
190°C/W, yielding a temperature rise of 0.4°C. Thermal rise
will be considerably less in either moving air or with direct
physical connection to a solid (or liquid) body.
MICROPROCESSOR A/D INTERFACE ISSUES
The AD22100 is especially well suited to providing a low cost
temperature measurement capability for microprocessor/
microcontroller based systems. Many inexpensive 8-bit micro-
processors now offer an onboard 8-bit ADC capability at a mod-
est cost premium. Total “cost of ownership” then becomes a
function of the voltage reference and analog signal conditioning
necessary to mate the analog sensor with the microprocessor
ADC. The AD22100 can provide an ideal low cost system by
eliminating the need for a precision voltage reference and any
additional active components. The ratiometric nature of the
AD22100 allows the microprocessor to use the same power sup-
ply as its ADC reference. Variations of hundreds of millivolts in
the supply voltage have little effect as both the AD22100 and
the ADC use the supply as their reference. The nominal
AD22100 signal range of 0.25 V to 4.75 V (–50°C to +150°C)
makes good use of the input range of a 0 V to 5 V ADC. A
single resistor and capacitor are recommended to provide im-
munity to the high speed charge dump glitches seen at many
microprocessor ADC inputs (see Figure 1).
Table I. Thermal Resistance (TO-92)
Medium
θJA (°C/Watt)
τ (sec) *
Aluminum Block
Moving Air**
60
2
Without Heat Sink
Still Air
75
3.5
15
An 8-bit ADC with a reference of 5 V will have a least signifi-
cant bit (LSB) size of 5 V/256 = 19.5 mV. This corresponds to
a nominal resolution of about 0.87°C.
Without Heat Sink
190
*The time constant τ is defined as the time to reach 63.2% of the final
temperature change.
**1200 CFM.
REV. B
–5–
AD22100
USE WITH A PRECISION REFERENCE AS THE SUPPLY
VOLTAGE
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
While the ratiometric nature of the AD22100 allows for system
operation without a precision voltage reference, it can still be
used in such systems. Overall system requirements involving
other sensors or signal inputs may dictate the need for a fixed
precision ADC reference. The AD22100 can be converted to
absolute voltage operation by using a precision reference as the
supply voltage. For example, a 5.00 V reference can be used to
power the AD22100 directly. Supply current will typically be
500 µA which is usually within the output capability of the refer-
ence. A large number of AD22100s may require an additional
op amp buffer, as would scaling down a 10.00 V reference that
might be found in “instrumentation” ADCs typically operating
from ±15 V supplies.
TO-92
0.205 (5.20)
0.135
(3.43)
MIN
0.175 (4.96)
0.210 (5.33)
0.170 (4.58)
SEATING PLANE
0.050
(1.27)
MAX
0.500
(12.70)
MIN
0.019 (0.482)
0.016 (0.407)
SQUARE
0.055 (1.39)
0.045 (1.15)
0.105 (2.66)
0.095 (2.42)
0.105 (2.66)
0.080 (2.42)
0.165 (4.19)
0.125 (3.94)
0.105 (2.66)
0.080 (2.42)
SO-8 (SOIC)
5
4
8
1
0.2440 (6.20)
0.2284 (5.80)
0.1574 (4.00)
0.1497 (3.80)
0.1968 (5.00)
0.1890 (4.80)
0.0196 (0.50)
× 45°
0.0688 (1.75) 0.0099 (0.25)
0.0532 (1.35)
0.0098 (0.25)
0.0040 (0.10)
0°-8°
0.0500 (1.27)
0.0160 (0.41)
0.0098 (0.25)
0.0075 (0.19)
0.0500
(1.27)
BSC
0.0192 (0.49)
0.0138 (0.35)
SEATING
PLANE
–6–
REV. B
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