MCP9701A Microchip Technology, MCP9701A Datasheet - Page 11

• Manufacturer Part Number: MCP9701A
• Description: (MCP9700A / MCP9701A) Low-Power Linear Active Thermistor ICs
• Manufacturer: Microchip Technology

4.0
The Linear Active Thermistor™ IC uses an internal
diode to measure temperature. The diode electrical
characteristics have a temperature coefficient that
provides a change in voltage based on the relative
ambient temperature from -40°C to 150°C. The change
in voltage is scaled to a temperature coefficient of
10.0 mV/°C (typical) for the MCP9700/9700A and
19.5 mV/°C (typical) for the MCP9701/9701A. The out-
put voltage at 0°C is also scaled to 500 mV (typical)
and 400 mV (typical) for the MCP9700/9700A and
MCP9701/9701A, respectively. This linear scale is
described in the first-order transfer function shown in
Equation 4-1
EQUATION 4-1:
FIGURE 4-1:
4.1
The MCP9700/9700A and MCP9701/9701A accuracy
can be improved by performing a system calibration at
a specific temperature. For example, calibrating the
system at +25°C ambient improves the measurement
accuracy to a ±0.5°C (typical) from 0°C to +70°C, as
shown in
relative temperature change, this family measures
temperature with higher accuracy.
© 2009 Microchip Technology Inc.
Where:
V
MCP9700
V
OUT
0°C
T
T
V
A
C
DD
APPLICATIONS INFORMATION
Improving Accuracy
V
= Ambient Temperature
= Sensor Output Voltage
= Sensor Output Voltage at 0°C
= Temperature Coefficient
SS
Figure
and
(See DC Electrical Characteristics
table)
(See DC Electrical Characteristics
table)
V
OUT
Figure
GND
V
4-2. Therefore, when measuring
OUT
MCP9700/9700A and MCP9701/9701A
=
SENSOR TRANSFER
FUNCTION
Typical Application Circuit.
T
2-16.
C
•
T
A
+
ANI
V
0°C
PICmicro®
MCU
V
DD
V
SS
FIGURE 4-2:
vs. Temperature.
The change in
temperature is due to the output non-linearity from the
first-order equation, as specified in
accuracy can be further improved by compensating for
the output non-linearity.
For higher accuracy using a sensor compensation
technique, refer to AN1001 “IC Temperature Sensor
Accuracy
Microcontroller” (DS01001). The application note
shows that if the MCP9700 is compensated in addition
to room temperature calibration, the sensor accuracy
can be improved to ±0.5°C (typical) accuracy over the
operating temperature
FIGURE 4-3:
Sensor Accuracy.
The compensation technique provides a linear
temperature reading. A firmware look-up table can be
generated to compensate for the sensor error.
-1.0
-2.0
-3.0
-2.0
-4.0
3.0
2.0
1.0
0.0
6.0
4.0
2.0
0.0
-50
-50
V
10 Samples
Spec. Limits
DD
Compensation
= 3.3V
-25
-25
accuracy
0
0
Relative Accuracy to +25°C
MCP9700/9700A Calibrated
(Figure
Temperature (°C)
25
25
T
A
(°C)
4-3).
with
from the calibration
50
50
www.DataSheet4U.com
Average
Equation
DS21942E-page 11
75
75
+ s
- s
a
100 Samples
100
100
PICmicro
4-2. The
125
125
®