MXR7202ML MEMSIC, MXR7202ML Datasheet - Page 5

• Manufacturer Part Number: MXR7202ML
• Description: ACCELEROMETER, 2 AXIS, ±2G, LCC8
• Manufacturer: MEMSIC

Specifications of MXR7202ML

• No. Of Axes: 2
• Sensor Case Style: LCC
• No. Of Pins: 8
• Supply Voltage Range: 2.7V To 5.25V
• Operating Temperature Range: -40°C To +105°C
• Operating Temperature Max: 105°C
• Acceleration Range: ±2g
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

EXTERNAL FILTERS
AC Coupling: For applications where only dynamic
accelerations (vibration) are to be measured, it is
recommended to ac couple the accelerometer output as
shown in Figure 2. The advantage of ac coupling is that
zero g offset variations from part to part and zero g offset
change over temperature can be eliminated. Figure 3 is a
HFP (high pass filter) with a –3dB breakpoint given by the
equation:
desirable to have the HFP –3dB point at a very low
frequency in order to detect very low frequency
accelerations. Sometimes the implementation of this HFP
may result in unreasonably large capacitors, and the
designer may turn to digital implementations of HFPs
where very low frequency –3dB breakpoints can be
achieved.
Low Pass Filter: An external low pass filter would be
useful in low frequency applications such as tilt or
inclination. The low pass filter limits the noise floor and
improves the resolution of the accelerometer. The low pass
filter shown in Figure 4 has a –3dB breakpoint given by the
equation:
device filter, C=0.1µF and R=8kΩ, ±5%, 1/8W.
MEMSIC MXR7202G/M Rev.C
A
A
A
A
O UTX
O UTY
O UTX
O UTY
f
f
=
=
1
1
2
2
Figure 2: High Pass Filter
π
π
Figure 3: Low Pass Filter
RC
RC
R
R
C
C
. In many applications it may be
. For the 200 Hz ratiometric output
R
R
C
C
Filtered
Filtered
Output
Output
A
Filtered
A
Filtered
O utput
O utput
A
O UTX
A
O UTY
O UTX
O UTY
Page 5 of 8
POWER SUPPLY NOISE REJECTION
One capacitor is recommended for best rejection of power
supply noise (reference Figure 4 below). The capacitor
should be located as close as possible to the device supply
pin (V
possible, and surface mount capacitor is preferred. For
typical applications, the capacitor can be ceramic 0.1 µF.
PCB LAYOUT AND FABRICATION SUGGESTIONS
1. Liberal use of ceramic bypass capacitors is
2. Robust low inductance ground wiring should be used.
3. Care should be taken to ensure there is “thermal
4. A metal ground plane should be added directly beneath
5. Vias can be added symmetrically around the ground
recommended. It is best to solder a 0.1uF capacitor
directly across V
symmetry” on the PCB immediately surrounding the
MEMSIC device and that there is no significant heat
source nearby.
the MEMSIC device. The size of the plane should be
similar to the MEMSIC device’s footprint and be as
thick as possible.
plane. Vias increase thermal isolation of the device
from the rest of the PCB.
DD
). The capacitor lead length should be as short as
Figure 4: Power Supply Noise Rejection
DD
and COM pin.
2
/26/2007