Page 1
3.3 V Supply, Voltage Output Temperature
V
S
V
OUT
Ι
R
T
a
FEATURES
3.3 V, Single Supply Operation
Temperature Coefficient of 28 mV/°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 × V
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
Sensor with Signal Conditioning
AD22103*
SIMPLIFIED BLOCK DIAGRAM
S
GENERAL DESCRIPTION
The 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 0.25 V at
0°C to +3.05 V at +100°C using a single +3.3 V supply.
Due to its ratiometric nature, the AD22103 offers a cost effective solution when interfacing to an analog-to-digital converter.
This is accomplished by using the ADC’s power supply as a reference to both the ADC and the AD22103 (See Figure 1),
eliminating the need for and cost of a precision reference.
Protected by U.S. Patent Nos. 5030849 and 5243319
*
.
AD22103
+3.3V
REFERENCE
SIGNAL OUTPUT
DIRECT TO ADC
V
O
1kΩ
0.1µF
INPUT
Figure 1. Application Circuit
ANALOG TO
DIGITAL
CONVERTER
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., 1995
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
REV. 0
Page 2
AD22103–SPECIFICATIONS
(TA = +25°C and VS = +2.7 V to +3.6 V unless otherwise noted)
AD22103K
Parameter Min Typ Max Units
TRANSFER FUNCTION V
TEMPERATURE COEFFICIENT (V
OUT
= (V
/3.3 V) × [0.25 V + (28 mV/°C) × T
S
/3.3 V) × 28 mV/°C
S
]V
A
TOTAL ERROR
Initial Error
= +25°C ±0.5 ±2.0 °C
T
A
Error over Temperature
T
A = TMIN
Nonlinearity
TA = T
to T
MAX
MIN to TMAX
±0.75 ±2.5 °C
0.1 0.5 % FS
1
OUTPUT CHARACTERISTICS
Nominal Output Voltage
V
= 3.3 V, T
S
V
= 3.3 V, T
S
VS = 3.3 V, T
= 0°C 0.25 V
A
= +25°C 0.95 V
A
= +100°C 3.05 V
A
POWER SUPPLY
Operating Voltage +2.7 +3.3 +3.6 V
Quiescent Current 350 500 600 µA
TEMPERATURE RANGE
Guaranteed Temperature Range 0 +100 °C
Operating Temperature Range 0 +100 °C
PACKAGE TO-92
SOIC
NOTES
1
FS (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 SPECIFICATIONS
(TA = +25°C and VS = +3.3 V unless otherwise noted)
Parameter Min Typ Max Units
TRANSFER FUNCTION V
TEMPERATURE COEFFICIENT (V
OUT
= (V
/3.3 V) × [0.25 V + (28 mV/°C) × T
S
/3.3 V) × 28 mV/°C
S
]V
A
OUTPUT CHARACTERISTICS
Error
= +25°C ±0.5 Note 1 °C
T
A
Nominal Output Voltage
T
= +25°C 0.95 V
A
POWER SUPPLY
Operating Voltage +2.7 +3.3 +3.6 V
Quiescent Current 350 500 600 µA
TEMPERATURE RANGE
Guaranteed Temperature Range 25 °C
Operating Temperature Range 0 +100 °C
NOTES
1
Max 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.
–2–
REV. 0
Page 3
AD22103
AD22103
BOTTOM VIEW
(Not to Scale)
PIN 1PIN 2PIN 3
GND V
O
V
S
1
2
3
4
8
7
6
5
TOP VIEW
(Not to Scale)
NC = NO CONNECT
AD22103
V
S
NC
NC
NC
NC
V
O
NC
GND
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +10 V
Reversed Continuous Supply Voltage . . . . . . . . . . . . . . . –10 V
Operating Temperature . . . . . . . . . . . . . . . . . . 0°C to +100°C
Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +160°C
Output Short Circuit to V
or Ground . . . . . . . . . . . . Indefinite
S
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 GUIDE
Guaranteed
Temperature Package Package
Model/Grade Range Description Option
AD22103KT 0°C to +100°C TO-92 TO-92
AD22103KR 0°C to +100°C SOIC SO-8
AD22103KChips* +25°C N/A N/A
*Minimum purchase quantities of 100 pieces for all chip orders.
PIN DESCRIPTION
Mnemonic Function
V
S
V
O
Power Supply Input
Device Output
GND Ground Pin Must Be Connected to 0 V
NC No Connect
PIN CONFIGURATIONS
TO-92
SOIC
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 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.
Typical Performance Curves
250
200
(SOIC)
150
– °C/W
JA
θ
100
(TO-92)
50
0 1200400 800
Figure 3. Thermal Resistance vs. Air Flow Rate
REV. 0
18
14
12
T (TO-92)
10
8
τ – Sec
6
T (SOIC)
4
2
0 1200400 800
FLOW RATE – CFM
Figure 2. Thermal Response vs. Air Flow Rate
–3–
WARNING!
ESD SENSITIVE DEVICE
FLOW RATE – CFM
Page 4
AD22103
V
OUT
V
S
Ι
THEORY OF OPERATION
The 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 resistor, similar to an RTD, which is built into the IC. Figure 4
shows a simplified block diagram of the AD22103.
OUTPUT STAGE CONSIDERATIONS
As 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 0.25 V at 0°C to +3.05 V
at +100°C. Furthermore, the AD22103 output pin is capable of
withstanding an indefinite short circuit to either ground or the
+V
S
power supply. These characteristics are provided by the output
stage structure shown in Figure 6.
Ι
V
OUT
R
T
Figure 4. Simplified Block Diagram
The temperature-dependent resistor, labeled RT, exhibits a
change in resistance that is nearly linearly proportional to temperature. This resistor is excited with a current source that is
proportional to power supply voltage. The resulting voltage
across R
is therefore both supply voltage proportional and lin-
T
early varying with temperature. The remainder of the AD22103
consists of an op amp signal conditioning block that takes the
voltage across R
and applies the proper gain and offset to
T
achieve the following output voltage function:
= (V
V
OUT
/3.3 V) × [0.25 V + (28.0 mV/°C) × T
S
]
A
ABSOLUTE ACCURACY AND NONLINEARITY
SPECIFICATIONS
Figure 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 28.0 mV/°C. Demanding applications can
achieve improved performance by calibrating these offset and
gain errors so that only the residual nonlinearity remains as a
The active portion of the output stage is a PNP transistor with
its emitter connected to the V
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 –100 µA. (Here,
“fixed” means the current sink is fairly insensitive to either supply voltage or output loading conditions. The current sink capability is a function of temperature, increasing its pull-down
capability at lower temperatures.)
Due to its limited current sinking ability, the AD22103 is incapable of driving loads to the V
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
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).
Figure 6. Output Stage Structure
supply and collector connected
S
power supply and is instead in-
S
power supply should be avoided as
S
source of error.
MOUNTING CONSIDERATIONS
2.5
2.0
1.5
1.0
0.5
0
ERROR – °C
–0.5
–1.0
–1.5
–2.0
–2.5
0 10050
TEMPERATURE – °C
VS = 3.6V
VS = 3.3V
VS = 2.7V
If 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 ceramic well should be used to shield the AD22103. 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.
Figure 5. Typical AD22103 Performance
REV. 0–4–
Page 5
AD22103
THERMAL ENVIRONMENT EFFECTS
The thermal environment in which the AD22103 is used determines two performance traits: the effect of self-heating on accuracy and the response time of the sensor to rapid changes in
temperature. In the first case, a rise in the IC junction temperature above the ambient temperature is a function of two variables;
the power consumption of the AD22103 and the thermal resistance between the chip and the ambient environment θ
. Self-
JA
heating error in degrees Celsius can be derived by multiplying
the power dissipation by θ
Because errors of this type can vary
JA.
widely for surroundings with different heat sinking capacities, it
is necessary to specify θ
under several conditions. Table I
JA
shows how the magnitude of self-heating error varies relative to
the environment. A typical part will dissipate about 1.5 mW at
room temperature with a 3.3 V supply and negligible output
loading. In still air, without a “heat sink,” the table below indicates a θ
of 190°C/W, yielding a temperature rise of 0.285°C.
JA
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)
Medium θJA (°C/Watt) τ (sec)*
Aluminum Block 60 2
Moving Air**
Without Heat Sink 75 3.5
Still Air
Without Heat Sink 190 15
*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
exponential function. Figure 7 shows typical response time plots for
a few media of interest.
100
90
80
70
60
50
40
30
% OF FINAL VALUES
20
10
0
0 10010
ALUMINUM
BLOCK
MOVING
AIR
STILL AIR
20 30 40 50 60 70 80 90
TIME – sec
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 ISSUES
The AD22103 is especially well suited to providing a low cost
temperature measurement capability for microprocessor/
microcontroller based systems. Many inexpensive 8-bit microprocessors now offer an onboard 8-bit ADC capability at a modest 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 supply 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 0 V to 3.3 V ADC. A
single resistor and capacitor are recommended to provide immunity 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 significant 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
VOLTAGE
While 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 3.3 V reference can be used to
power the AD22103 directly. Supply current will typically be
500 µA 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 10.00 V reference that
might be found in “instrumentation” ADCs typically operating
from ±15 V supplies.
USING THE AD22103 WITH ALTERNATIVE SUPPLY
VOLTAGES
Because of its ratiometric nature the AD22103 can be used at
other supply voltages. Its nominal transfer function can be recalculated based on the new supply voltage. For instance, if using the
AD22103 at V
= 5 V the transfer function would be given by:
S
Figure 7. Response Time
The time constant
τ
is dependent on θ
and the specific heat
JA
capacities of the chip and the package. Table I lists the effective
τ
(time to reach 63.2% of the final value) for a few different
media. Copper printed circuit board connections were
REV. 0
–5–
V
V
V
S
=
O
O
=
5V
V
5V
0.25V +
S
0.378 V +
28 m
V
°C
42.42 mV
°C
×T
A
×T
5V
3.3V
A
Page 6
AD22103
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
TO-92
SEATING
PLANE
0.105 (2.66)
0.095 (2.42)
0.105 (2.66)
0.080 (2.42)
0.105 (2.66)
0.080 (2.42)
0.1968 (5.00)
0.1890 (4.80)
0.135
(3.43)
MIN
0.500
(12.70)
MIN
123
BOTTOM VIEW
SO-8 (SOIC)
0.205 (5.20)
0.175 (4.96)
0.210 (5.33)
0.170 (4.38)
0.019 (0.482)
0.016 (0.407)
SQUARE
0.055 (1.39)
0.045 (1.15)
0.165 (4.19)
0.125 (3.94)
0.050
(1.27)
MAX
C2006–18–3/95
0.2440 (6.20)
0.2284 (5.80)
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
85
0.1574 (4.00)
0.1497 (3.80)
41
0.0688 (1.75)
PIN 1
0.0532 (1.35)
0.0192 (0.49)
0.0500
(1.27)
0.0138 (0.35)
BSC
0.0098 (0.25)
0.0075 (0.19)
0.0196 (0.50)
0.0099 (0.25)
8°
0°
x 45°
0.0500 (1.27)
0.0160 (0.41)
PRINTED IN U.S.A.
REV. 0–6–
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