Application Notes

Freescale Semiconductor
Application Note
Document Number: AN4992
Rev 1.0, 12/2014
Upgrading from the MMA7330L to
the FXLN83xxQ
Contents
1 Introduction
1
Introduction................................................................1
The FXLN83xxQ accelerometers expand Freescale's portfolio,
adding best-in-class analog performance. These
accelerometers are designed to support analog capability for
industrial, medical, and tamper-detection applications.
Additionally, these accelerometers provide interface
compatibility and simplicity for low-voltage microcontrollers
(MCUs). The FXLN83xxQ accelerometers are designed
specifically for the Industrial market and are, therefore, part of
Freescale's Longevity Program.
2
Key Benefits of using FXLN83xxQ..........................2
3
Upgrade Guide...........................................................3
The FXLN83xL analog accelerometer replaces the previous
generation MMA73xxL Analog 3-axis accelerometer.
This document describes the necessary steps to transition from
the MMA73xxL 3-axis Analog Accelerometer family to the
new FXLN83xxQ 3-Axis Analog Industrial Accelerometer to
bring best-in-class power consumption and bandwidth to your
analog applications.
© 2014 Freescale Semiconductor, Inc.
Key Benefits of using FXLN83xxQ
2 Key Benefits of using FXLN83xxQ
Improved battery life in portable applications by reducing overall power consumption:
Specification
MMA7330L
FXNL83xxQ
Units
Current consumption
400
180
μA
Supply voltage range
2.2 – 3.6
1.71 – 3.6
V
MMA7330L
FXNL83xxQ
Units
400 XY
2700 XY
300 Z
600 Z
±12
±16
g
Sensitivity @ ±4 g
308
114.51
mV/g
Noise Density
350
200 XY, 280 Z (130 XY, 200 Z)
μg/√Hz
MMA7330L
FXNL83xxQ
Units
Output Impedance
32
10
kΩ
Nonratiometric output
No
Yes
VBYP
No
Yes
Enhanced user experience through performance improvements:
Specification
Max Bandwidth
Max g-Range
Hz
1. Can be improved by connecting VBYP to the VRefHigh input of your ADC
Enhanced analog output performance:
Specification
Additional features and performance improvements:
Specification
Package
MMA7330L
FXNL83xxQ
Units
3 x 5 x 1, 14-Pin LGA
3 x 3 x 1, 12-pin QFN
mm
Output at 0 g
1.4
0.75
V
Cross-Axis Sensitivity
±5
±4.2
%
–40 to 85
–40 to 105
°C
Operating Temperature
A major feature of the FXLN83xxQ is its nonratiometric output. This means that VDD fluctuations, within the VDD
specification for the part, will not change the output offset voltage or sensitivity. Therefore, a noisy power supply will not
cause noisy output, thus resulting in a cleaner system. An additional benefit of nonratiometric output is that, when powered
by a battery, the device will not suffer from signal drop off when the battery voltage drops as the stored energy is consumed.
Previously with the MMA7330L, and with many other analog accelerometers currently on the market, the sensor's output was
ratiometric to VDD. This meant that the output of the sensor was proportional to VDD and as the supply voltage fluctuated so
did the output of the sensor. Using a ratiometric part required the user to monitor VDD and perform additional calculations to
Upgrading from the MMA7330L to the FXLN83xxQ, Rev 1.0, 12/2014
2
Freescale Semiconductor, Inc.
Upgrade Guide
compensate for fluctuations or changes, such as the previously mentioned battery drop off. With the FXLN83xxQ, such extra
effort is a thing of the past as the VBYP output on the FXLN83xxQ can be used as the full scale range input to the system
ADC to improve performance. In general, the 0 g output from any of the XYZ axes will be equal to 1/2 of the VBYP output.
3 Upgrade Guide
Upgrading to the FXLN83xxQ requires changes to the PCB, including adapting the layout to accept a 3x3x1 12-pin QFN
package, rerouting the existing traces, and adding a trace for the VBYP pin.
NC
NC
1
XOUT
YOUT
13
Self Test
2
12
NC
3
11
NC
14
NC NC
12
BYP 1
g-Select
ZOUT
4
10
VSS
5
9
NC
VDD
6
8
NC
7
11
10
XOUT
VDD
2
9
YOUT
ST
3
8
ZOUT
EN
4
7
GND
5
6
g-Select GND
Sleep
MMA7330L
FXLN83xxQ
Table 1. Pinout Comparison
MMA7330L
Pin
Name
2
XOUT
3
YOUT
4
FXLN83xxQ
Function
Pin
Name
X axis output voltage
10
XOUT
X axis output voltage
Y axis output voltage
9
YOUT
Y axis output voltage
ZOUT
Z axis output voltage
8
ZOUT
Z axis output voltage
6
VDD
Power Supply Voltage
2
VDD
Supply voltage
1,8,9,11,
12,14
NC
No internal connection, leave
floating
11-12
NC
No internal connection
10
g-Select
Logic input pin to select g level
5
g-Select
13
Self-test
Input pin to initiate Self Test
3
ST
5
VSS
6-7
GND
7
Sleep
4
EN
Power enable pin, enabled when
logic high
1
VBYP1
Internal voltage regulator output
capacitor connection
Connect to Ground
Sleep mode pin, enabled when
logic low
Function
g-Range selection pin. Logic low:
High-g mode, Logic High: Low-g
mode
Self-test enable pin, enabled when
logic high
Connect to Ground
1. The VBYP output on the FXLN83xxQ can be used as the full scale range input to an ADC to improve performance. The
benefits of using this output are described in the section, Key Benefits of using FXLN83xxQ.
Upgrading from the MMA7330L to the FXLN83xxQ, Rev 1.0, 12/2014
Freescale Semiconductor, Inc.
3
Upgrade Guide
3.1 Hardware Setup
Based on Table 1, most of the traces will have to be rerouted to replace the MMA7330L with the FXLN83xxQ. The
following should be considered when redesigning a PCB originally built for the MMA7330L:
• The pin used for Sleep in the MMA7330L will be named EN and is enabled when logic high (connected to VDD).
• The pin named VSS will be named GND and will continue to be connected to ground.
• The addition of the VBYP pin will require a new trace. The single 0.1 µF capacitor between VDD and VSS/GND should
be replaced with a 1.0 µF and a 0.1 µF (each with their own trace from Vdd to GND).
3.2 Capacitor Changes
The capacitors on the XOUT, YOUT, and ZOUT branches are different on the FXLN83xxQ than on the MMA7330L. Use
capacitors as recommended in Table 2.
Table 2. Recommended Minimum Capacitance Specifications
Part Number
Bandwidth
C4 (pF)
C5 (pF)
C6 (pF)
Low
9100
9100
9100
FXLN8362Q
Low
9100
9100
9100
FXLN8371Q
High
8200
3300
3300
FXLN8372Q
High
8200
3300
3300
FXLN8361Q
XOUT
C6
XOUT
YOUT
ZOUT
GND
10
9
YOUT
8
7
C5
ZOUT
C4
Upgrading from the MMA7330L to the FXLN83xxQ, Rev 1.0, 12/2014
4
Freescale Semiconductor, Inc.
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© 2014 Freescale Semiconductor, Inc.
Document Number AN4992
Revision 1.0, 12/2014
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