MCP9700 Microchip Technology, Inc., MCP9700 Datasheet - Page 10

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

MCP9700/01
4.4
The MCP9700/01 measures temperature by monitor-
ing the voltage of a diode located in the die. A low
impedance thermal path between the die and the PCB
is provided by the pins. Therefore, the MCP9700/01
effectively monitors the temperature of the PCB.
However, the thermal path for the ambient air is not as
efficient because the plastic device package functions
as a thermal insulator from the die. This limitation
applies
sensors. If the application requires measuring ambient
air, the PCB needs to be designed with proper thermal
conduction to the sensor pins.
The MCP9700/01 is designed to source/sink 100 µA
(max.). The power dissipation due to the output current
is relatively insignificant. The effect of the output
current can be described using Equation 4-2.
EQUATION 4-2:
At T
tion of I
the self-heating due to power dissipation (T
0.179°C.
DS21942A-page 10
Where:
T
T
θ
V
I
I
V
OUT
DD
A
JA
J
OUT
DD
A
T
= +25°C (V
J
–
DD
= Junction Temperature
= Ambient Temperature
= Package Thermal Resistance (331°C/W)
= Sensor Output Voltage
= Sensor Output Current
= Operating Current
= Operating Voltage
Thermal Considerations
T
to
A
= 12 µA, V
=
plastic-packaged
θ
JA
OUT
(
V
= 0.75V) and maximum specifica-
DD
DD
EFFECT OF SELF-
HEATING
I
DD
= 5.5V and I
+
(
V
DD
silicon
–
V
OUT
OUT
temperature
)
= +100 µA,
I
OUT
J
– T
)
A
) is
© 2005 Microchip Technology Inc.