2005-2016 Microchip Technology Inc. DS20001942G-page 9
MCP9700/9700A and MCP9701/9701A
4.2 Shutdown Using Microcontroller
I/O Pin
The 6 µA (typical) low operating current of the
MCP9700/9700A and MCP9701/9701A family makes it
ideal for battery-powered applications. However, for
applications that require a tighter current budget, this
device can be powered using a microcontroller
Input/Output (I/O) pin. The I/O pin can be toggled to
shut down the device. In such applications, the micro-
controller internal digital switching noise is emitted to
the MCP9700/9700A and MCP9701/9701A as power
supply noise. However, this switching noise compro-
mises measurement accuracy, therefore a decoupling
capacitor and series resistor will be necessary to filter
out the system noise.
4.3 Layout Considerations
The MCP9700/9700A and MCP9701/9701A family of
sensors 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
DD
and GND pins. In high-noise applications, connect
the power supply voltage to the V
DD
pin using a
200 resistor with a 1 µF decoupling capacitor. A high
frequency ceramic capacitor is recommended. It is nec-
essary that the capacitor is located as close as possible
to the V
DD
and GND pins in order to provide effective
noise protection. In addition, avoid tracing digital lines
in close proximity to the sensor.
4.4 Thermal Considerations
The MCP9700/9700A and MCP9701/9701A family
measures temperature by monitoring 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 sensor 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 to plastic-packaged
silicon temperature sensors. If the application requires
the measurement of ambient air, the TO-92 package
should be considered.
The MCP9700/9700A and MCP9701/9701A sensors
are 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 by Equation 4-2.
EQUATION 4-2: EFFECT OF
SELF-HEATING
At T
A
=+25°C (V
OUT
= 0.75V) and maximum
specification of I
DD
=12µA, V
DD
=5.5V and
I
OUT
= +100 µA, the self-heating due to power
dissipation (T
J
–T
A
) is 0.179°C.
T
J
T
A
–
JA
V
DD
I
DD
V
DD
V
OUT
–+ I
OUT
=
Where:
T
J
= Junction Temperature
T
A
= Ambient Temperature
JA
=
Package Thermal Resistance (331°C/W)
V
OUT
= Sensor Output Voltage
I
OUT
= Sensor Output Current
I
DD
= Operating Current
V
DD
= Operating Voltage
