www.fairchildsemi.com
FM20
Ultra-Low-Power Analog Temperature Sensor
Features
•
•
•
•
•
•
•
Analog Output, -11.77mV/°C
Range, -55 to 130°C
Accuracy, ±1°C at 25°C
Supply Current, 9µA typical
Output Drive, 1µA
Self-heating < 0.021°C
Operating Voltage: +2.4V to +6V
Description
As a precision CMOS temperature sensor, the FM20 is
cost-effective for accurate low-power temperature
monitoring applications. Output voltage versus temperature
is extremely linear. With no load, the supply current is
typically 1µA. For normal operation, the load on V
OUT
should be 5M
Ω
or less.
In a typical application, a remotely mounted FM20 is
monitored by a microcontroller with an analog A/D
converter input. Alternatively, the FM20 can drive a
comparator with a high impedance input.
Accuracy is typically ±1°C at room temperature; and better
than ±2.5°C from 0 to 50°C.
Available packages are surface mount 5-pin SC70 and 3-pin
SOT-23.
Applications
•
•
•
•
•
•
•
•
Mobile Phones
Computers
Battery Management
Office Equipment
HVAC
Power Supply Modules
Disk Drives
Automotive
Thermal Response
V
OUT
(mV)
1863.9
391
-50 -40
-25
0
25
50
75
100
125
Temperature (˚C)
Temperature (˚C) =
V
OUT
– 1863.9mV
–11.77mV/˚C
FM20 Output Voltage vs. Temperature
REV. 1.0.6 1/9/03
FM20
PRODUCT SPECIFICATION
Pin Assignments
V
OUT
3
GND
2
N/C
1
GND
3
FM20
4
V
DD
5
GND
FM20
1
V
DD
2
V
OUT
Pin Descriptions
Pin No.
Pin Name SC-70 SOT-23
V
OUT
3
2
Type
Analog Output
Function
Temperature Sense.
Analog output voltage indicating
temperature.
V
OUT
= 1863.9 – 11.77 T(°C) mV
Supply Voltage.
2.4 to 6.0V
Ground.
V
DD
GND
4
2, 5
1
3
Power
Power
2
REV. 1.0.6 1/9/03
PRODUCT SPECIFICATION
FM20
Absolute Maximum Ratings
1
Parameter
Supply Voltage
Output Voltage
Output Current
Storage Temperature Range
Lead Soldering Temperature
ESD
2
Human Body Model
Machine Model
Min.
Typ.
Max.
+7
V
DD
+ 0.5
-20/+1
+150
220
2000
250
Units
V
V
µA
°C
°C
V
V
-60
Notes:
1. Absolute maximum ratings are limits beyond which operation may cause permanent damage to the device. These are stress
ratings only; functional operation at or above these limits is not implied.
2. Human Body Model: 100pF capacitor discharged through a 1.5k
Ω
resistor into each pin. Machine Model: 200pF capacitor
discharged directly into each pin.
Electrical Characteristics
3
Limits apply for -55°C
≤
T
A
≤
+130°C and V
DD
= +5.0V unless otherwise noted.
Parameter
Transfer Characteristic
Sensitivity
Output at 0°C
Accuracy
4
Symbol
Conditions
Min
Typ
-11.77
1863.9
±1
±2
±2
Max
Units
mV/°C
mV
°C
°C
°C
°C
°C
mV
µA
mA
µA
k
Ω
mV/mA
pF
V
µA
µA
°C
°C
T
A
= +25°C
T
A
= -55°C (T
MIN
)
T
A
= +130°C (T
MAX
)
Temperature Range
Non-Linearity
5
Output
Output Voltage Range
Output Current Source
6
Output Current Sink
6
Output resistance
Load regulation
Capacitive Load
7
Power
Supply Voltage
Quiescent Supply Current
Output Floating
Package
Self Heating
-2
-3
-5
-55
-0.5
300
+2
+3
+5
+130
+0.2
2550
I
ONSN
I
ONSG
I
OL
V
OUT
< V
DD
Sensing
Surge
T
A
= 25°C
1
20
C
L
V
DD
I
DD
100
2.4
T
A
= +25°C
-55°C
≤
T
A
≤
+130°C
SOT-23
SC70
9
9
1000
6.0
11.5
14
0.02016
0.02082
Notes:
3. These specifications are guaranteed only for the test conditions listed.
4. Accuracy (expressed in °C) = Difference between calculated output voltage and measured output voltage. Calculated output
voltage = -11.77mV/°C multiplied by device’s case temperature at specified conditions of temperature, voltage and power
supply plus an offset of 1863.9 mV at 0°C.
5. Non-linearity is defined as the deviation of the output-voltage-versus-temperature curve from the best-fit straight line, over the
device's rated temperature range.
6. Lowest output current should be targeted; higher currents result in more self-heating of the device.
7. High capacitive loads may be driven by the output in a static mode, but it may require a delay time before initial read at power
up to allow for the RC time constant of the charging capacitor.
REV. 1.0.6 1/9/03
3
FM20
PRODUCT SPECIFICATION
Typical Performance Characteristics
Quiescent Current (µA)
12
11
10
9
8
7
6
-50
-25
0
25
50
75
100
125
V
DD
= +5V
Temperature (°C)
Figure 1. Quiescent Current vs. Temperature
3
2
Accuracy (°C)
1
0
-1
-2
-3
-4
-5
-50
0
lower spec limit
50
Temperature (°C)
V
DD
=+5V
upper spec limit
100
Figure 2. Accuracy vs. Temperature
Applications Information
Mounting
The FM20 can be easily mounted by gluing or cementing it
to a surface. In this case, its temperature will be within about
0.2°C of the temperature of the surface it is attached to if the
ambient air temperature is almost the same as the surface
temperature. If the air temperature is much higher or lower
than the surface temperature, the actual temperature of the
FM20 die will be at an intermediate temperature between the
surface temperature and the air temperature.
To ensure good thermal conductivity, the backside of the
FM20 die is directly attached to the GND pin. The lands and
traces to the FM20 will, of course, be part of the printed
circuit board, which is the object whose temperature is being
measured. These printed circuit board lands and traces will
not cause the FM20’s temperature to deviate from the desired
temperature.
Alternatively, the FM20 can be mounted inside a sealed-end
metal tube, and can then be dipped into a bath or screwed
into a threaded hole in a tank. As with any IC, the FM20 and
4
accompanying wiring and circuits must be kept insulated and
dry to avoid leakage and corrosion. This is especially true if
the circuit may operate at cold temperatures where condensa-
tion can occur. Printed-circuit coatings and varnishes such as
Humiseal and epoxy paint or dips can be used to ensure that
moisture cannot corrode the FM20 or its connections.
Loading
The FM20 will handle sizable capacitive loads up to 300pF
without any special considerations. In an extremely noisy
environment it may be advisable to add some filtering to
minimize noise in the output voltage. It is also recommended
that a 0.1µF bypass capacitor be added between the supply
voltage and ground. This is due to the instant current demand
caused by switching CMOS transistors. Normally it is un-
advisable to put a sufficiently large supply (particularly in
portable electronics) to be able to handle the dynamic cur-
rents of CMOS transistors. It is a much simpler solution to
use a bypass capacitor to sustain the supply voltage during
this short demand period.
REV. 1.0.6 1/9/03
PRODUCT SPECIFICATION
FM20
In environments that are particularly noisy it may be neces-
sary to add a low-pass filter network to the output of the
device. As shown below, a 1µF capacitor in addition to the
output impedance of the device and a 200
Ω
series resistor
for a low-pass filter that will pass the slow thermal time con-
stant of the FM20, while filtering the higher frequency noise.
The response time of the FM20 can be affected by this filter
network, therefore values for C
FILTER
< 1500pF are recom-
mended.
GND
0.1µF
Bypass
Cap
V
DD
V
OUT
C
FILTER
R
FILTER
C
L
GND
0.1µF
Bypass
Cap
V
DD
V
OUT
R
FILTER
C
FILTER
C
L
Figure 3. FM20 with Filter Network for Noisy Environments or for Capacitive Loads Greater than 300pF
Table 1. Resistor/Capacitor Combinations for Filter Network
R
FILTER
200
Ω
470
Ω
680
Ω
1000
Ω
10k
Ω
100k
Ω
C
FILTER
1µF
0.1µF
0.01µF
1000pF
100pF
10pF
REV. 1.0.6 1/9/03
5
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