Instrukcja obsługi Microchip MCP9803

Microchip Niesklasyfikowane MCP9803

Przeczytaj poniżej 📖 instrukcję obsługi w języku polskim dla Microchip MCP9803 (10 stron) w kategorii Niesklasyfikowane. Ta instrukcja była pomocna dla 9 osób i została oceniona przez 2 użytkowników na średnio 4.5 gwiazdek

Pobierz PDF
Strona 1/10
2010-2015 Microchip Technology Inc. DS00001001C-page 1
AN1001
INTRODUCTION
Microchip Technology Inc. provides a number of analog
and serial output Integrated Circuit (IC) temperature
sensors. Typically, these sensors are accurate at room
temperature within one degree Celsius (±1°C). How-
ever, at hot or cold temperature extremes, the accuracy
decreases nonlinearly. Normally, that nonlinearity has a
parabolic shape.
This application note derives an equation to describe
the typical nonlinear characteristics of a sensor, which
is used to determine compensation for the sensor's
accuracy error over a specified range of operating tem-
peratures. A PIC® microcontroller unit (MCU) can
compute the equation and provide a temperature read-
ing with higher accuracy.
This application note is based on MCP9700 and
MCP9701 analog-output temperature sensors and
MCP9800 serial-output temperature sensors.
SOLUTION APPROACH
Silicon characterization data is used to determine the
nonlinear sensor characteristics. From this data, an
equation is derived that describes the typical perfor-
mance of a sensor. When the corresponding coeffi-
cients for the equation are determined, the coefficients
are used to compute the compensation for the typical
sensor’s nonlinearity.
The error distribution is provided using an average and
±1 standard deviation (± before and after compensa-
tion. A total of 100 devices were used as representative
for the MCP9700 and MCP9701, while 160 devices
were used for the MCP9800.
Figure 1 shows the typical sensor accuracy before and
after compensation. It illustrates that the compensation
provides an accurate and linear temperature reading
over the sensor operating temperature range.
A PIC MCU is used to compute the equation and
compensate the sensor output to provide a linear
temperature reading.
FIGURE 1: Typical Sensor Accuracy Before and After Compensation.
Author: Ezana Haile
Microchip Technology Inc.
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
-55 -35 -15 5 25 45 65 85 105 125
Temperature (°C)
Typical Accuracy (°C)
Sensor Accuracy
Compensated Sensor Accuracy
IC Temperature Sensor Accuracy Compensation
with a PIC® Microcontroller
AN1001
DS00001001C-page 2 2010-2015 Microchip Technology Inc.
SENSOR ACCURACY
The typical sensor accuracy over the operating tem-
perature range has an accuracy error curve. At hot and
cold temperatures, the magnitude of the error increases
exponentially, resulting in a parabolic-shaped error
curve. The following figures show the average and ±1°C
standard deviation of the sensor accuracy curve for the
MCP9800, MCP9700 and MCP9701 sensors.
FIGURE 2: MCP9800 Accuracy
(160 parts).
FIGURE 3: MCP9700 Accuracy
(100 parts).
FIGURE 4: MCP9701 Accuracy
(100 parts).
The accuracy specification limits for these sensors are
published in the corresponding data sheets as plotted
in Figure 2, Figure 3 and Figure 4. Note that due to the
sensor nonlinearity at temperature extremes, the accu-
racy specification limits are widened. The reduced
accuracy at temperature extremes can be
compensated to improve sensor accuracy over the
range of operating temperatures.
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
-55 -35 -15 5 25 45 65 85 105 125
Temperature (°C)
Accuracy (°C)
+
V
V
V
VV
Average
-
V
V
V
VV
Spec. Limit
-4.0
-2.0
0.0
2.0
4.0
6.0
-55 -35 -15 5 25 45 65 85 105 125
Temperature (°C)
Accuracy (°C)
+
V
V
V
VV
Average
-
V
V
V
VV
Spec. Limit
-4.0
-2.0
0.0
2.0
4.0
6.0
-15 5 25 45 65 85 105 125
Temperature (°C)
Accuracy (°C)
+
V
V
V
VV
Average
-
V
V
V
VV
Spec. Limit
2010-2015 Microchip Technology Inc. DS00001001C-page 3
AN1001
SENSOR THEORY
Temperature sensors use a fully turned-on PNP tran-
sistor to sense the ambient temperature. The voltage
drop across the base-emitter junction has the charac-
teristics of a diode. The junction drop is temperature
dependent, which is used to measure the ambient tem-
perature. Equation 1 shows a simplified equation that
describes the diode forward voltage.
EQUATION 1: DIODE FORWARD
VOLTAGE
IS is a constant variable defined by the transistor size.
A constant forward current (IF) is used to bias the
diode, which makes the temperature T
A the only
changing variable in the equation. However, I
S varies
significantly over process and temperature. The varia-
tion makes it impossible to reliably measure the
ambient temperature using a single transistor.
To minimize IS dependency, a two-diode solution is
used. If both diodes are biased with constant forward
currents of IF1 and IF2
, and the currents have a ratio of
N (IF2/IF1 = N), the difference between the forward volt-
ages (V
F) has no dependency on the saturation cur-
rents of the two diodes, as shown in Equation 2. V
F is
also called Voltage Proportional to Absolute
Temperature (VPTAT).
EQUATION 2: VPTAT
VPTAT provides a linear voltage change with a slope of
(86 µV/°C)*ln(N)|N=10 = 200 µV/°C. The voltage is either
amplified for analog output sensors or is interfaced to an
Analog-to-Digital Converter (ADC) for digital sensors.
The accuracy of VPTAT over the specified temperature
range depends on the matching of both forward current
(IF
) and saturation current (IS) of the two sensors [1].
Any mismatch in these variables creates inaccuracy in
the temperature measurement. The mismatch contrib-
utes to the temperature error or nonlinearity. The non-
linearity is described using a 2nd order polynomial
equation.
VF
kTA
q
--------- IF
IS
-----
 
 
ln=
Where:
k = Boltzmann’s Constant (1.3807 x 10-23 J/K)
q = Electron Charge (1.602 x 10-19 coulombs)
TA= Ambient Temperature
IF= Forward Current
IS= Saturation Current
,IFIS
»
VFVF1 VF2
–=
VF
kT A
q
--------- ln
IF1
IS
-------
N IF1
IS
-----------------
-----------------=
VF
kTA
q
--------- ln
N =
VFVPTAT
=
Where:
VF= Forward Voltages
IF= Forward Currents
VPTAT = Voltage Proportional to Absolute
Temperature

Specyfikacje produktu

Marka: Microchip
Kategoria: Niesklasyfikowane
Model: MCP9803

Potrzebujesz pomocy?

Jeśli potrzebujesz pomocy z Microchip MCP9803, zadaj pytanie poniżej, a inni użytkownicy Ci odpowiedzą


Instrukcje Niesklasyfikowane Microchip

Microchip

Microchip AT91SAM9M11 Instrukcja

15 Stycznia 2025
Microchip

Microchip AT91SAM9261 Instrukcja

15 Stycznia 2025
Microchip

Microchip AT91SAM9CN12 Instrukcja

15 Stycznia 2025
Microchip

Microchip ATA5749C Instrukcja

15 Stycznia 2025
Microchip

Microchip ATECC508A Instrukcja

15 Stycznia 2025
Microchip

Microchip ATECC608C-TNGTLS Instrukcja

15 Stycznia 2025
Microchip

Microchip ATECC608C-TCSM Instrukcja

15 Stycznia 2025
Microchip

Microchip ATMXT144UD-SL Instrukcja

15 Stycznia 2025
Microchip

Microchip ATMXT1296M1 Instrukcja

15 Stycznia 2025
Microchip

Microchip ATMEGA162 Instrukcja

15 Stycznia 2025

Instrukcje Niesklasyfikowane

Najnowsze instrukcje dla Niesklasyfikowane

GBC

GBC ThermaBind T500Pro Instrukcja

15 Stycznia 2025
Da-Lite

Da-Lite Parallax 29850 Instrukcja

15 Stycznia 2025
Crivit

Crivit IAN 290909 Instrukcja

15 Stycznia 2025
Tripp Lite

Tripp Lite SmartRack SRW12US Instrukcja

15 Stycznia 2025
Powerfix

Powerfix IAN 280221 Instrukcja

15 Stycznia 2025
AGM

AGM Rattler TC35-640 Instrukcja

15 Stycznia 2025
AGM

AGM Wolf-7 Pro Instrukcja

15 Stycznia 2025
AGM

AGM Anaconda TC50-640 Instrukcja

15 Stycznia 2025
AGM

AGM Secutor Pro TS50-640 Instrukcja

15 Stycznia 2025
Vogel's

Vogel's RISE A122 Instrukcja

15 Stycznia 2025