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AD844ANZ , 60 MHz 2000 V Monolithic Op Amp
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AD22103
Voltage Output 3.3 V Temperature Sensor withSignal Conditioning
REV.0
3.3 V Supply, Voltage Output Temperature
Sensor with Signal Conditioning
FEATURES
3.3 V, Single Supply Operation
Temperature Coefficient of 28mV/°C
100°C Temperature Span (0°C to +100°C)
Accuracy Better Than 2.5% of Full Scale
Linearity Better Than 0.5% of Full Scale
Output Proportional to Temperature × VS
Minimal Self-Heating
High Level, Low Impedance Output
Reverse Supply Protected
APPLICATIONS
Microprocessor Thermal Management
Battery and Low Powered Systems
Power Supply Temperature Monitoring
System Temperature Compensation
Board Level Temperature Sensing
MARKETS
Computers
Portable Electronic Equipment
Industrial Process Control
Instrumentation
SIMPLIFIED BLOCK DIAGRAM
GENERAL DESCRIPTIONThe AD22103 is a monolithic temperature sensor with on-chip
signal conditioning. It can be operated over the temperature
range 0°C to +100°C, making it ideal for use in numerous 3.3 V
applications.
The signal conditioning eliminates the need for any trimming,
buffering or linearization circuitry, greatly simplifying the system
design and reducing the overall system cost.
The output voltage is proportional to the temperature times the
supply voltage (ratiometric). The output swings from 0.25V at
0°C to +3.05V at +100°C using a single +3.3V supply.
Due to its ratiometric nature, the AD22103 offers a cost effec-
tive solution when interfacing to an analog-to-digital converter.
This is accomplished by using the ADC’s power supply as a ref-
erence to both the ADC and the AD22103 (See Figure 1),
eliminating the need for and cost of a precision reference.
*. Patent Nos. 5030849 and 5243319.
+3.3VFigure 1.Application Circuit
AD22103–SPECIFICATIONSPACKAGE
NOTESFS (Full Scale) is defined as that of the operating temperature range, 0°C to +100°C. The listed max specification limit applies to the guaranteed temperature range.
For example, the AD22103K has a nonlinearity of (0.5%) × (100°C) = 0.5°C over the guaranteed temperature range of 0°C to +100°C.
Specifications subject to change without notice.
CHIP SPECIFICATIONSNOTESMax specs cannot be guaranteed on chips, however, performance once assembled should be commensurate with the specifications listed in the top table.
Specifications subject to change without notice.
(TA = +25°C and VS = +2.7V to +3.6V unless otherwise noted)
(TA = +25°C and VS = +3.3V unless otherwise noted)
ABSOLUTE MAXIMUM RATINGS*SupplyVoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+10V
Reversed Continuous Supply Voltage . . . . . . . . . . . . . . .–10V
Operating Temperature . . . . . . . . . . . . . . . . . .0°C to +100°C
Storage Temperature . . . . . . . . . . . . . . . . . . .–65°C to +160°C
Output Short Circuit to VS or Ground . . . . . . . . . . . .Indefinite
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . .+300°C
*Stresses 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.
ORDERING GUIDEAD22103KR
*Minimum purchase quantities of 100 pieces for all chip orders.
PIN DESCRIPTION
PIN CONFIGURATIONS
TO-92
SOIC
–
FLOW RATE – CFM1200400800Figure 2.Thermal Response vs. Air Flow Rate
FLOW RATE – CFM
1001200400800Figure 3.Thermal Resistance vs. Air Flow Rate
Typical Performance Curves
CAUTIONESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD22103 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.
AD22103
THEORY OF OPERATIONThe AD22103 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 AD22103.
+VS
VOUTFigure 4.Simplified Block Diagram
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 AD22103
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:
VOUT = (VS/3.3V) × [0.25V + (28.0mV/°C) × TA]
ABSOLUTE ACCURACY AND NONLINEARITY
SPECIFICATIONSFigure 5 graphically depicts the guaranteed limits of accuracy
for the AD22103 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 28.0mV/°C. Demanding applications can
achieve improved performance by calibrating these offset and
gain errors so that only the residual nonlinearity remains as a
source of error.
ERROR –
TEMPERATURE – °C
OUTPUT STAGE CONSIDERATIONSAs previously stated, the AD22103 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
3.3 V, the output voltage extends from 0.25V at 0°C to +3.05V
at +100°C. Furthermore, the AD22103 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.
Figure 6.Output Stage Structure
The active portion of the output stage is a PNP transistor with
its emitter connected to the VS 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 –100μA. (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.)
Due to its limited current sinking ability, the AD22103 is inca-
pable of driving loads to the VS power supply and is instead in-
tended to drive grounded loads. A typical value for short circuit
current limit is 7mA, so devices can reliably source 1mA ormA. However, for best output voltage accuracy and minimal
internal self-heating, output current should be kept below 1mA.
Loads connected to the VS power supply should be avoided as
the current sinking capability of the AD22103 is very limited.
These considerations are typically not a problem when driving
a microcontroller analog to digital converter input pin (see
MICROPROCESSOR A/D INTERFACE ISSUES).
MOUNTING CONSIDERATIONSIf the AD22103 is thermally attached and properly protected, it
can be used in any measuring situation where the maximum
range of temperatures encountered is between 0°C and +100°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 conductive epoxy
or glue is recommended for typical mounting conditions. In wet
or corrosive environments, an electrically isolated metal or ce-
ramic well should be used to shield the AD22103. Because the
part has a voltage output (as opposed to current), it offers mod-
est immunity to leakage errors, such as those caused by conden-
sation at low temperatures.
THERMAL ENVIRONMENT EFFECTSThe thermal environment in which the AD22103 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 variables;
the power consumption of the AD22103 and the thermal resis-
tance between the chip and the ambient environment θJA. Self-
heating error in degrees Celsius 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 necessary to specify θJA under several conditions. Table I
shows how the magnitude of self-heating error varies relative to
the environment. A typical part will dissipate about 1.5mW at
room temperature with a 3.3V supply and negligible output
loading. In still air, without a “heat sink,” the table below indi-
cates a θJA of 190°C/W, yielding a temperature rise of 0.285°C.
Thermal rise will be considerably less in either moving air or
with direct physical connection to a solid (or liquid) body.
Table I.Thermal Resistance (TO-92)*The time constant τ is defined as the time to reach 63.2% of the final
temperature change.
**1200 CFM.
Response of the AD22103 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.
TIME – sec
% OF FINAL VALUES30405060708090Figure 7.Response Time
The time constant τ is dependent on θJA and the specific heat
capacities of the chip and the package. Table I lists the effec-
tive τ (time to reach 63.2% of the final value) for a few different
neglected in the analysis; however, they will sink or conduct
heat directly through the AD22103’s solder plated copper leads.
When faster response is required, a thermally conductive grease
or glue between the AD22103 and the surface temperature
being measured should be used.
MICROPROCESSOR A/D INTERFACE ISSUESThe AD22103 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 AD22103 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
AD22103 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 AD22103 and
the ADC use the supply as their reference. The nominal
AD22103 signal range of 0.25 V to 3.05 V (0°C to +100°C)
makes good use of the input range of a 0V to 3.3 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).
An 8-bit ADC with a reference of 3.3 V will have a least signifi-
cant bit (LSB) size of 3.3 V/256 = 12.9 mV. This corresponds
to a nominal resolution of about 0.46°C/bit.
USE WITH A PRECISION REFERENCE AS THE SUPPLY
VOLTAGEWhile the ratiometric nature of the AD22103 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 AD22103 can be converted to
absolute voltage operation by using a precision reference as the
supply voltage. For example, a 3.3V reference can be used to
power the AD22103 directly. Supply current will typically be
500μA which is usually within the output capability of the refer-
ence. A large number of AD22103s may require an additional
op amp buffer, as would scaling down a 10.00V reference that
might be found in “instrumentation” ADCs typically operating
from ±15V supplies.
USING THE AD22103 WITH ALTERNATIVE SUPPLY
VOLTAGESBecause of its ratiometric nature the AD22103 can be used at
other supply voltages. Its nominal transfer function can be recal-
culated based on the new supply voltage. For instance, if using the
AD22103 at VS = 5 V the transfer function would be given by: =VS0.25V+28mV×TA
3.3V=VS0.378V+42.42mV×TA
AD22103C2006–18–3/95
PRINTED IN U.S.A.
OUTLINE DIMENSIONSDimensions shown in inches and (mm).
TO-92
0.105 (2.66)
0.080 (2.42)
0.105 (2.66)
0.080 (2.42)
0.165 (4.19)
0.125 (3.94)
SQUARE
0.019 (0.482)
0.016 (0.407)
0.105 (2.66)
0.095 (2.42)
0.055 (1.39)
0.045 (1.15)
SEATING
PLANE
(12.70)
MIN
0.205 (5.20)
0.175 (4.96)
0.210 (5.33)
0.170 (4.38)3
BOTTOM VIEW
(3.43)
MIN
(1.27)
MAX
SO-8 (SOIC)
PIN 1
0.2440 (6.20)
0.2284 (5.80)
SEATING
PLANE
0.0098 (0.25)
0.0040 (0.10)
0.0192 (0.49)
0.0138 (0.35)
0.0688 (1.75)
0.0532 (1.35)
(1.27)
BSC
0.0098 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
0.0196 (0.50)
0.0099 (0.25)x 45°
