MMA6271QT Datasheet, PDF (5/11 Pages) Freescale Semiconductor, Inc – ±2.5g - 10g Two Axis Low-g Micromachined Accelerometer

BASIC CONNECTIONS
Pin Descriptions
Top View
g-Select1 1
g-Select2 2
V_DD 3
V_SS 4
16 15 14 13
12 Sleep Mode
11 N/C
10 N/C
9 N/C
5678
Figure 4. Pinout Description
Table 4. Pin Descriptions
Pin No.
1
2
3
4
5-7
8 - 11
12
13
14
15
16
Pin Name
Description
g-Select1 Logic input pin to select g level.
g-Select2 Logic input pin to select g level.
V_DD
Power Supply Input
V_SS
Power Supply Ground
N/C
No internal connection.
Leave unconnected.
N/C
Unused for factory trim.
Leave unconnected.
Sleep Mode Logic input pin to enable product or
Sleep Mode.
N/C
No internal connection.
Leave unconnected.
Y_OUT
X_OUT
N/C
Y direction output voltage.
X direction output voltage.
No internal connection.
Leave unconnected.
Logic
Inputs
1
g-Select1
V_DD
0.1 µF
Logic
Input
2 g-Select2
MMA6271QT
3 _VDD
Y_OUT ^{14 1 kΩ}
4 _VSS
12
Sleep Mode
0.1 µF
X_OUT ^{15 1 kΩ}
0.1 µF
Figure 5. Accelerometer with Recommended
Connection Diagram
PCB Layout
POWER SUPPLY
V_DD
C
V_SS
Sleep Mode
g-Select1
V_RH
C
P0
P1
g-Select2
P2
X_OUT
Y_OUT
R
C
R
C
A/D_IN
A/D_IN
V_DD
C
V_SS
Figure 6. Recommended PCB Layout for Interfacing
Accelerometer to Microcontroller
NOTES:
1. Use 0.1 µF capacitor on V_DD to decouple the power
source. Do not exceed capacitor values of 2.2 or
3.3 µF on V_DD-GND.
2. Physical coupling distance of the accelerometer to
the microcontroller should be minimal.
3. The flag underneath the package is internally
connected to ground. It is not recommended for the
flag to be soldered down.
4. Place a ground plane beneath the accelerometer to
reduce noise, the ground plane should be attached to
all of the open ended terminals shown in Figure 6.
5. Use an RC filter with 1.0 kΩ and 0.1 µF on the
outputs of the accelerometer to minimize clock noise
(from the switched capacitor filter circuit).
6. PCB layout of power and ground should not couple
power supply noise.
7. Accelerometer and microcontroller should not be a
high current path.
8. A/D sampling rate and any external power supply
switching frequency should be selected such that
they do not interfere with the internal accelerometer
sampling frequency (11 kHz for the sampling
frequency). This will prevent aliasing errors.
9. PCB layout should not run traces or vias under the
QFN part. This could lead to ground shorting to the
accelerometer flag.
Sensors
Freescale Semiconductor
MMA6271QT
5