MCP9804 Microchip Technology, MCP9804 Datasheet - Page 35

• Manufacturer Part Number: MCP9804
• Description: Accuracy Digital Temperature Sensor
• Manufacturer: Microchip Technology

6.0
6.1
The MCP9804 does not require any additional
components besides the master controller in order to
measure temperature. However, it is recommended
that a decoupling capacitor of 0.1 µF to 1 µF be used
between the V
ceramic capacitor is recommended. It is necessary for
the capacitor to be located as close as possible to the
power and ground pins of the device in order to provide
effective noise protection.
In addition, good PCB layout is key for better thermal
conduction from the PCB temperature to the sensor
die. For good temperature sensitivity, add a ground
layer under the device pins as shown in
FIGURE 6-1:
© 2009 Microchip Technology Inc.
APPLICATIONS INFORMATION
Layout Considerations
DD
and GND pins. A high-frequency
DFN Package Layout (Top View).
Alert
GND
SDA
SCL
Figure
6-1.
EP9
6.2
A potential for self-heating errors can exist if the
MCP9804 SDA, SCL and Event lines are heavily
loaded with pull-ups (high current). Typically, the
self-heating error is negligible because of the relatively
small current consumption of the MCP9804. A
temperature accuracy error of approximately 0.5°C
could result from self-heating if the communication pins
sink/source the maximum current specified.
For example, if the Event output is loaded to maximum
I
of self-heating.
EQUATION 6-1:
At room temperature (T
I
power dissipation T
and 0.5°C for the TSSOP-8 package.
OL
DD
T
Where:
Δ
V
,
=
I
= 500 µA and V
OL_Alert, SDA
OL_Alert, SDA
Equation 6-1
θ
JA
(
Thermal Considerations
V
DD
V
A0
A1
A2
θ
•
DD
T
T
T
I
JA
DD
A
Δ
J
+
= T
= Junction Temperature
= Ambient Temperature
= Package Thermal Resistance
= Alert and SDA Output V
= Alert and SDA Output I
can be used to determine the effect
V
DD
Δ
OL_Alert
(0.4 V
(3 mA
J
is 0.2°C for the DFN-8 package
EFFECT OF
SELF-HEATING
- T
= 3.6V, the self-heating due to
A
A
max
max
•
= +25°C) with maximum
I
OL_Alert
MCP9804
)
)
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+
DS22203A-page 35
V
OL_SDA
OL
OL
•
I
OL_SDA
)