Datasheet

MCP9501/2/3/4
DS22268A-page 10 © 2011 Microchip Technology Inc.
4.1.2 POWER SUPPLY REJECTION
The MCP9501/2/3/4 family does not require any
additional components. However, it is recommended
that a decoupling capacitor of 0.1 µF to 1 µF be used
between the V
DD
and GND pins. A high-frequency
ceramic capacitor is recommended. It is necessary for
the capacitor to be located as close as possible to the
power pins in order to provide effective noise
protection.
FIGURE 4-5: Power-supply Filter using a
Single Resistor.
For applications where a switching regulator is used to
power the sensor, it is recommended to add a 200Ω
resistor in series to V
DD
to filter out the switcher noise.
It is also recommended to add the series resistor in
applications where a linear regulator is used to
step-down a switching regulator voltage to power the
sensor, as shown in Figure 4-5. For example, if a
linearly regulated 3.3V from a 5V switching regulator is
used to power the sensor, add a 200Ω series resistor.
The MCP9501/2/3/4 family of sensors is designed to
prevent false output trigger due to high frequency
power supply or system noise. Figure 4-6 shows the
device performance with a high frequency signal added
on V
DD
. The output is not triggered due to the signal
added on V
DD
. With some applications, it is
recommended to add a bypass capacitor of 0.1 µF to
1µF.
FIGURE 4-6: Power Supply Rejection.
V
DD
200Ω
MCP9501/2/3/4
Switching
Regulator
0.1 µF
bypass
V
DD
200Ω
MCP9501/2/3/4
Switching
Regulator
0.1 µF
bypass
Regulator
Linear
0
1
2
3
4
5
6
10 100 1000 10000 100000 1000000 10000000
O
u
t
p
u
t
V
o
l
t
a
g
e
(
V
)
Frequency (Hz)
MCP9501/2/3/4 T
SET
= 25\C Power Supply Rejection
No False Trigger
1
0
k
1
0
0
k
1
M
1
0
M
1
k
1
0
0
1
0
V
DD
= 5V + 400mV
AC
V
DD
= 5V + 400mV
SQR
T
SET
= 25\C
T
A
= 23\C
°
°
°
Frequency (Hz)
Output Voltage (V)