Freescale Semiconductor, Inc.
PCB Layout
BASIC CONNECTIONS
STATUS
P1
16
15
14
13
12
11
10
9
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
V
1
2
3
4
5
6
7
8
SS
V
SS
V
SS
ST
P0
V
SS
V
OUT
A/D IN
R
V
OUT
STATUS
C
0.1 µF
C
1 kΩ
0.1 µF
V
SS
V
DD
V
DD
V
SS
C
0.1 µF
V
DD
V
RH
ST
C
0.1 µF
Figure 4. Pinout Description
POWER SUPPLY
Pin No.
Pin Name
Description
1 thru 3
V
SS
Redundant connections to the internal
V
and may be left unconnected.
Figure 6. Recommended PCB Layout for Interfacing
Accelerometer to Microcontroller
SS
4
5
6
7
8
V
Output voltage of the accelerometer.
Logic output pin used to indicate fault.
The power supply input.
OUT
STATUS
V
DD
V
The power supply ground.
SS
NOTES:
ST
Trim pins
—
Logic input pin used to initiate self–
test.
•
•
•
Use a 0.1 µF capacitor on V
source.
to decouple the power
DD
9 thru 13
Used for factory trim.
Leave unconnected.
Physical coupling distance of the accelerometer to the mi-
crocontroller should be minimal.
14 thru 16
No internal connection.
Leave unconnected.
Place a ground plane beneath the accelerometer to reduce
noise, the ground plane should be attached to all internal
V
terminals shown in Figure 4.
SS
5
•
Use an RC filter of 1 kΩ and 0.1 µF on the output of the ac-
celerometer to minimize clock noise (from the switched
capacitor filter circuit).
MMA1250D
STATUS
V
DD
LOGIC
INPUT
8
6
ST
R1
1 kΩ
4
OUTPUT
SIGNAL
V
V
OUT
DD
•
•
•
PCB layout of power and ground should not couple power
supply noise.
V
1
2
3
SS
C1
0.1 µF
V
SS
C2
V
SS
Accelerometer and microcontroller should not be a high
current path.
0.1 µF
7
V
SS
A/Dsamplingrateandanyexternalpowersupplyswitching
frequency should be selected such that they do not inter-
fere with the internal accelerometer sampling frequency.
This will prevent aliasing errors.
Figure 5. SOIC Accelerometer with Recommended
Connection Diagram
2–28
www.motorola.com/semiconductors
Motorola Sensor Device Data
For More Information On This Product,
Go to: www.freescale.com
MOTOROLA [ MOTOROLA ]
