MCP9700 Microchip Technology, Inc., MCP9700 Datasheet - Page 9

• Manufacturer Part Number: MCP9700
• Description: Low-Power Voltage output temperature sensor
• Manufacturer: Microchip Technology, Inc.

4.0
4.1
The MCP9700/01 accuracy can be improved by
performing a system calibration at a specific tempera-
ture. For example, calibrating the system at 25°C
ambient improves the measurement accuracy to a
±0.5°C (typ.) from 0°C to 70°C, as shown in Figure 4-1.
Therefore, when measuring relative temperature
change, this family measures temperature with higher
accuracy.
FIGURE 4-1:
vs. Temperature.
The relative change in accuracy from the calibration
temperature is due to the output non-linearity from the
first-order equation, specified in Equation 3-1. The
accuracy can be further improved by compensating for
the output non-linearity.
For higher accuracy, the sensor output transfer function
is also derived using a second-order equation as
shown in Equation 4-1. The equation describes the
output non-linearity. This equation is not used to
characterize the part as specified in the DC Electrical
Characteristics table; however, it provides better
accuracy.
EQUATION 4-1:
© 2005 Microchip Technology Inc.
V
OUT
Where:
-1.0
-2.0
-3.0
3.0
2.0
1.0
0.0
= T
= -T
APPLICATIONS INFORMATION
Improving Accuracy
T
V
V
T
T
-50
C2
A
C1
C2
OUT
0°C
C2
V
10 Samples
DD
(T
T
= 3.3V
A
A
-25
= Ambient Temperature
= Sensor Output Voltage
= Sensor Output Voltage at 0°C
= Temperature Coefficient
= Temperature Coefficient
2
+ 10°C)(125°C – T
+ (T
(refer to Figure 2-7 and 2-10)
(refer to Figure 2-8 and 2-11)
(refer to Figure 2-9 and 2-12)
MCP9700 1.4 µV/°C
MCP9701 2.7 µV/°C
C1
0
Relative Accuracy to +25°C
SECOND-ORDER
TRANSFER FUNCTION
+ 115 T
25
T
A
(°C)
C2
50
)T
A
) + T
A
+ 1250 T
75
C1
2
2
(typ.)
(typ.)
T
100
A
+ V
C2
+ V
0°C
125
0°C
4.2
The MCP9700/01 low operating current of 6 µA (typ.)
makes it ideal for battery-powered applications.
However, for applications that require tighter current
budget, this device can be powered using a microcon-
troller Input/Output (I/O) pin. The I/O pin can be toggled
to shutdown the device. In such applications, the
microcontroller internal digital switching noise is
emitted to the MCP9700/01 as power supply noise.
This switching noise compromises measurement
accuracy. Therefore, a decoupling capacitor will be
necessary.
4.3
The MCP9700/01 does not require any additional
components to operate. However, it is recommended
that a decoupling capacitor of 0.1 µF to 1 µF be used
between the V
tions, connect the power supply voltage to the V
using a 200Ω resistor with a 1 µF decoupling capacitor.
A high-frequency ceramic capacitor is recommended. It
is necessary for the capacitor to be located as close as
possible to the V
effective noise protection. In addition, avoid tracing dig-
ital lines in close proximity to the sensor.
Shutdown Using Microcontroller
I/O Pin
Layout Considerations
DD
DD
and GND pins. In high-noise applica-
and GND pins in order to provide
MCP9700/01
DS21942A-page 9
DD
pin