MEMSIC MXD2002A/B Rev.E
Page 7 of 8
5/15/2004
TEMPERATURE OUTPUT NOISE REDUCTION
It is recommended that a simple RC low pass filter is used
when measuring the temperature output. Temperature
output is typically a very slow changing signal, so a very
low frequency filter eliminates erroneous readings that may
result from the presence of higher frequency noise. A
simple filter is shown in Figure 8.
Filtered TOUT
8.2K
0.1uF
MEMSIC
Accel.
TOUT
Figure 8: Temperature Output Noise Reduction
POWER SUPPLY NOISE REJECTION
Two capacitors and a resistor are recommended for best
rejection of power supply noise (reference Figure 9 below).
The capacitors should be located as close as possible to the
device supply pins (VDA, VDD). The capacitor lead length
should be as short as possible, and surface mount capacitors
are preferred. For typical applications, capacitors C1 and
C2 can be ceramic 0.1 µF, and the resistor R can be 10 Ω.
In 5V applications where power consumption is not a
concern, maximum supply noise rejection can be obtained
by significantly increasing the values of C1, C2 and R. For
example, C1 = C2 = 0.47 µF and R = 270 Ω will virtually
eliminate power supply noise effects.
R
MEMSIC
Accelerometer
VDA
C1
C2
VDD
V SUPPLY
Figure 9: Power Supply Noise Rejection
PCB LAYOUT AND FABRICATION SUGGESTIONS
1. The Sck pin should be grounded to minimize noise.
2. Liberal use of ceramic bypass capacitors is
recommended.
3. Robust low inductance ground wiring should be used.
4. Care should be taken to ensure there is “thermal
symmetry” on the PCB immediately surrounding the
MEMSIC device and that there is no significant heat
source nearby.
5. A metal ground plane should be added directly beneath
the MEMSIC device. The size of the ground plane
should be similar to the MEMSIC device’s footprint
and as thick as possible.
6. Vias can be added symmetrically around the ground
plane. Vias increase thermal isolation of the device
from the rest of the PCB
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