Dual Axis SPI Inertial Sensor

Document Number: MMA65XX
Rev. 3, 03/2012
Freescale Semiconductor
Data Sheet: Technical Information
Dual-Axis SPI Inertial Sensor
MMA65xx, a SafeAssure solution, is a SPI-based, dual-axis, medium-g, overdamped lateral accelerometer designed for use in Automotive Airbag systems.
MMA65xx
Features
•
•
•
•
•
•
•
•
±80g, ±105g or ±120g full-scale range, independently specified for each axis
3.3V or 5V single supply operation
SPI-compatible serial interface
12-bit digital signed or unsigned SPI data output
Independent programmable arming functions for each axis
Twelve low-pass filter options, ranging from 50 Hz to 1000 Hz
Optional offset cancellation with > 6s averaging period and < 0.25 LSB/s slew
rate
Pb-Free 16-Pin QFN, 6 by 6 Package
Referenced Documents
•
AECQ100, Revision G, dated May 14, 2007 (http://www.aecouncil.com/)
ORDERING INFORMATION
Device
X-Axis Range
Y-Axis Range
Shipping
MMA6519KW
±80g
±80g
Tubes
MMA6525KW
±105g
±105g
Tubes
MMA6527KW
±120g
±120g
Tubes
MMA6519KWR2
±80g
±80g
Tape & Reel
MMA6525KWR2
±105g
±105g
Tape & Reel
MMA6527KWR2
±120g
±120g
Tape & Reel
For user register array programming, please consult your Freescale
representative.
© 2011-2012 Freescale Semiconductor, Inc. All rights reserved.
Bottom View
16 LEAD QFN
6 mm by 6 mm
CASE 2086-01
VCC
VCC
CS
VREG
SCLK
VREGA
MOSI
MISO
C1
C3
C2
MMA65xx
VSSA
VSS
VPP/TEST
ARM_X
ARM_Y
Figure 1. Application Diagram
Table 1. External Component Recommendations
Ref Des
Type
Description
Purpose
C1
Ceramic
0.1 μF, 10%, 10V Minimum, X7R
VCC Power Supply Decoupling
C2
Ceramic
1 μF, 10%, 10V Minimum, X7R
Voltage Regulator Output Capacitor (CVREG)
C3
Ceramic
1 μF, 10%, 10V Minimum, X7R
Voltage Regulator Output Capacitor (CVREGA)
MMA65xx
2
Sensor
Freescale Semiconductor, Inc.
VCC
VREG
VREGA
VSS
Offset
IIR
Low-Pass Filter
SINC Filter
Over-Damped
Y-Axis g-Cell
Linear
Interpolation
Compensation
Cancellation
Output
Scaling
ARM_Y
ARM_Y
Offset
Monitor
Clock CRC
Y-Axis
SPI
Generation
Y-Axis Register
Array
ΣΔ
Converter
VREG
Clock & bias
Generator
VREGA
VCC
CS
SPI
1 MHz
Self
Test
Analog
Regulator
Clock
8 MHz
1 MHz
Oscillator
Voltage
Monitor Regulator Monitoring
VREGA
OTP
Array
Memory
SPI
Mismatch
Verification
I/O
SCLK
MOSI
MISO
VREG
Clock & bias
Generator
Over-Damped
X-Axis g-Cell
Digital
ΣΔ
Converter
X-Axis Register
Array
X-Axis
Clock CRC
SPI
Generation
Offset
Monitor
IIR
SINC Filter
Low-Pass Filter
Compensation
Linear
Interpolation
Offset
Cancellation
Output
Scaling
ARM_X
ARM_X
xxxxxxx
xxxxxxx
X: 0 g
Y: -1 g
X: +1 g
Y: 0 g
xxxxxxx
xxxxxxx
xxxxxxx
xxxxxxx
Figure 2. Internal Block Diagram
X: 0 g
Y: +1 g
xxxxxxx
xxxxxxx
X: -1 g
Y: 0 g
X: 0 g
Y: 0 g
X: 0 g
Y: 0 g
EARTH GROUND
Figure 3. Device Orientation Diagram
MMA65xx(K)W
AWLYWWZ
Data Code Legend:
A: Assembly Location
WL: Wafer Lot Number (g-cell Lot Number)
Y: Year
WW: Work Week
Z: Assembly Lot Number
Figure 4. Part Marking
MMA65xx
Sensor
Freescale Semiconductor, Inc.
3
VSSA
N/C
N/C
Pin Connections
VSSA
1
16 15 14 13
VREGA 1
12 CS
17
VSS 2
11 MOSI
VREG 3
10 SCLK
9 VCC
5
6
7
8
ARM_Y/PCM_Y
ARM_X/PCM_X
TEST/VPP
MISO
VSS 4
Figure 5. Top View, 16-Pin QFN Package
Table 2. Pin Descriptions
Pin
Pin
Name
Formal Name
1
VREGA
Analog
Supply
2
VSS
Digital GND
3
VREG
Digital
Supply
4
VSS
Digital GND
This pin is the power supply return node for the digital circuitry.
ARM_Y/
PCM_Y
Y-Axis
Arm Output /
PCM Output
The function of this pin is configurable via the DEVCFG register as described in Section 3.1.6.6. When the
arming output is selected, ARM_Y can be configured as an open drain, active low output with a pullup current;
or an open drain, active high output with a pulldown current. Alternatively, this pin can be configured as a
digital output with PCM signal proportional to the Y axis acceleration data. Reference Section 3.8.10 and
Section 3.8.11. If unused, this pin must be left unconnected.
6
ARM_X/
PCM_X
X-Axis
Arm Output /
PCM Output
The function of this pin is configurable via the DEVCFG register as described in Section 3.1.6.6. When the
arming output is selected, ARM_X can be configured as an open drain, active low output with a pullup current;
or an open drain, active high output with a pulldown current. Alternatively, this pin can be configured as a
digital output with a PCM signal proportional to the X-axis acceleration data. Reference Section 3.8.10 and
Section 3.8.11. If unused, this pin must be left unconnected.
7
TEST /
VPP
Programming
Voltage
This pin provides the power for factory programming of the OTP registers. This pin must be connected to VSS
in the application.
8
MISO
SPI Data Out
This pin functions as the serial data output for the SPI port.
9
VCC
Supply
This pin supplies power to the device. An external capacitor must be connected between this pin and VSS.
Reference Figure 1.
10
SCLK
SPI Clock
This input pin provides the serial clock to the SPI port. An internal pulldown device is connected to this pin.
11
MOSI
SPI Data In
This pin functions as the serial data input to the SPI port. An internal pulldown device is connected to this pin.
5
Definition
This pin is connected to the power supply for the internal analog circuitry. An external capacitor must be
connected between this pin and VSSA. Reference Figure 1.
This pin is the power supply return node for the digital circuitry.
This pin is connected to the power supply for the internal digital circuitry. An external capacitor must be
connected between this pin and VSS. Reference Figure 1.
12
CS
Chip Select
This input pin provides the chip select for the SPI port. An internal pullup device is connected to this pin.
13
VSSA
Analog GND
This pin is the power supply return node for analog circuitry.
14
NC
No Connect
Not internally connected. This pin can be unconnected or connected to VSS in the application.
15
NC
No Connect
Not internally connected. This pin can be unconnected or connected to VSS in the application.
16
VSSA
Analog GND
This pin is the power supply return node for analog circuitry.
17
PAD
Die Attach
Pad
Corner Pads
This pin is the die attach flag, and is internally connected to VSS. Reference Section 5 for die attach pad
connection details.
The corner pads are internally connected to VSS.
MMA65xx
4
Sensor
Freescale Semiconductor, Inc.
2
Electrical Characteristics
2.1
Maximum Ratings
Maximum ratings are the extreme limits to which the device can be exposed without permanently damaging it.
#
Rating
Symbol
Value
Unit
1
Supply Voltage
VCC
-0.3 to +7.0
V
(3)
2
VREG, VREGA
VREG
-0.3 to +3.0
V
(3)
3
SCLK, CS, MOSI,VPP/TEST
VIN
-0.3 to VCC + 0.3
V
(3)
4
ARM_X, ARM_Y
VIN
-0.3 to VCC + 0.3
V
(3)
5
MISO (high impedance state)
VIN
-0.3 to VCC + 0.3
V
(3)
6
Powered Shock (six sides, 0.5 ms duration)
gpms
±1500
g
(5,18)
7
Unpowered Shock (six sides, 0.5 ms duration)
gshock
±2000
g
(5,18)
8
Drop Shock (to concrete surface)
hDROP
1.2
m
(5)
9
10
11
Electrostatic Discharge
Human Body Model (HBM)
Charge Device Model (CDM)
Machine Model (MM)
VESD
VESD
VESD
±2000
±750
±200
V
V
V
(5)
(5)
(5)
12
Storage Temperature Range
Tstg
-40 to +125
°C
(5)
13
Thermal Resistance - Junction to Case
qJC
2.5
°C/W
(14)
2.2
Operating Range
The operating ratings are the limits normally expected in the application and define the range of operation.
#
Characteristic
14
15
Supply Voltage
Standard Operating Voltage, 3.3V
Standard Operating Voltage, 5.0V
16
Operating Ambient Temperature Range
Verified by 100% Final Test
17
Power-on Ramp Rate (VCC)
Symbol
Min
Typ
Max
VCC
VL
+3.135
VTYP
+3.3
+5.0
VH
+5.25
TA
TL
-40
—
VCC_r
0.000033
—
Units
V
V
(15)
(15)
TH
+105
C
(1)
3300
V/μs
(19)
MMA65xx
Sensor
Freescale Semiconductor, Inc.
5
2.3
Electrical Characteristics - Power Supply and I/O
VL ≤ (VCC - VSS) ≤ VH, TL ≤ TA ≤ TH, |ΔTA| < 25 K/min unless otherwise specified
#
Characteristic
18 Supply Current
19
20
21
22
23
24
25
26
Power Supply Monitor Thresholds (See Figure 9)
VCC Under Voltage (Falling)
VREG Under Voltage (Falling)
VREG Over Voltage (Rising)
VREGA Under Voltage (Falling)
VREGA Over Voltage (Rising)
Power Supply Monitor Hysteresis
VCC Under Voltage
VREG Under Voltage, VREG Over Voltage
VREGA Under Voltage, VREGA Over Voltage
Power Supply RESET Thresholds
(See Figure 6, and Figure 9)
VREG Under Voltage RESET (Falling)
27
VREG Under Voltage RESET (Rising)
28
29
VREG RESET Hysteresis
30
31
Internally Regulated Voltages
VREG
VREGA
32
33
External Filter Capacitor (CVREG, CVREGA)
Value
ESR (including interconnect resistance)
34
35
Power Supply Coupling
50 kHz ≤ fn ≤ 300 kHz
4 MHz ≤ fn ≤ 100 MHz
Symbol
Min
Typ
Max
Units
IDD
4.0
—
8.0
mA
(1)
VCC_UV_f
VREG_UV_f
VREG_OV_r
VREGA_UV_f
VREGA_OV_r
2.74
2.10
2.65
2.20
2.65
—
—
—
—
—
3.02
2.25
2.85
2.35
2.85
V
V
V
V
V
(3,6)
(3,6)
(3,6)
(3,6)
(3,6)
VHYST
VHYST
VHYST
65
20
20
100
100
100
110
210
150
mV
mV
mV
(3)
(3)
(3)
*
*
VREG_UVR_f
VREG_UVR_r
VHYST
1.764
1.876
80
—
—
—
2.024
2.152
140
V
V
mV
(3,6)
(3,6)
(3)
*
*
VREG
VREGA
2.42
2.42
2.50
2.50
2.58
2.58
V
V
(1,3)
(1,3)
CVREG, CVREGA
ESR
700
—
1000
—
1500
400
nF
mΩ
(19)
(19)
—
—
—
—
0.004
0.004
LSB/mv
LSB/mv
(19)
(19)
*
*
*
*
*
*
Output High Voltage (MISO, PCM_X, PCM_Y)
36 3.15V ≤ (VCC - VSS) ≤ 3.45V (ILoad = -1 mA)
37 4.75V ≤ (VCC - VSS) ≤ 5.25V (ILoad = -1 mA)
*
*
VOH_3
VOH_5
VCC - 0.2
VCC - 0.4
—
—
—
—
V
V
(2,3)
(2,3)
Output Low Voltage (MISO, PCM_X, PCM_Y)
38 3.15V ≤ (VCC - VSS) ≤ 3.45V (ILoad = 1 mA)
39 4.75V ≤ (VCC - VSS) ≤ 5.25V (ILoad = 1 mA)
*
*
VOL_3
VOL_5
—
—
—
—
0.2
0.4
V
V
(2,3)
(2,3)
Open Drain Output High Voltage (ARM_X, ARM_Y)
40 3.15V ≤ (VCC - VSS) ≤ 3.45V (IARM = -1 mA)
41 4.75V ≤ (VCC - VSS) ≤ 5.25V (IARM = -1 mA)
*
*
VODH_3
VODH_5
VCC - 0.2
VCC - 0.4
—
—
—
—
V
V
(2,3)
(2,3)
Open Drain Output Pulldown Current (ARM_X, ARM_Y)
42 3.15V ≤ (VCC - VSS) ≤ 3.45V (VARM = 1.5V)
43 4.75V ≤ (VCC - VSS) ≤ 5.25V (VARM = 1.5V)
*
*
IODPD_3
IODPD_5
50
50
—
—
100
100
μA
μA
(2,3)
(2,3)
Open Drain Output Low Voltage (ARM_X, ARM_Y)
44 3.15V ≤ (VCC - VSS) ≤ 3.45V (IARM = 1 mA)
45 4.75V ≤ (VCC - VSS) ≤ 5.25V (IARM = 1 mA)
*
*
VODH_3
VODH_5
—
—
—
—
0.2
0.4
V
V
(2,3)
(2,3)
Open Drain Output Pullup Current (ARM_X, ARM_Y)
46 3.15V ≤ (VCC - VSS) ≤ 3.45V (VARM = 1.5V)
47 4.75 V ≤ (VCC - VSS) ≤ 5.25V (VARM = 1.5V)
*
*
IODPU_3
IODPU_5
-100
-100
—
—
-50
-50
μA
μA
(2,3)
(2,3)
48 Input High Voltage CS, SCLK, MOSI
*
VIH
2.0
—
—
V
(3,6)
49 Input Low Voltage CS, SCLK, MOSI
*
VIL
—
—
1.0
V
(3,6)
50 Input Voltage Hysteresis CS, SCLK, MOSI
*
VI_HYST
0.125
—
0.500
V
(19)
*
*
IIH
IIL
-70
30
-50
50
-30
70
μA
μA
(2,3)
(2,3)
51
52
Input Current
High (at VIH) (SCLK, MOSI)
Low (at VIL) (CS)
MMA65xx
6
Sensor
Freescale Semiconductor, Inc.
2.4
Electrical Characteristics - Sensor and Signal Chain
VL ≤ (VCC - VSS) ≤ VH, TL ≤ TA ≤ TH, |ΔTA| < 25 K/min unless otherwise specified.
#
Characteristic
53
54
55
Digital Sensitivity (SPI)
80g (12-Bit Output)
105.5g (12-Bit Output)
120g (12-Bit Output)
56
57
58
Sensitivity Error
TA = 25°C
-40°C ≤ TA ≤ 105°C
-40°C ≤ TA ≤ 105°C,VCC_UV_f ≤ VCC - VSS ≤ VL
Symbol
Min
Typ
Max
Units
*
*
*
SENS
SENS
SENS
—
—
—
24.0
18.2
16.0
—
—
—
LSB/g
LSB/g
LSB/g
(1,9)
(1,9)
(1,9)
*
*
ΔSENS
ΔSENS
ΔSENS
-4
-5
-5
—
—
—
+4
+5
+5
%
%
%
(1)
(1)
(3)
59a
60a
61a
62a
Offset at 0g (105.5g 120g Range, No Offset Cancellation)
12 bits, unsigned
*
12 bits, signed
*
12 bits, unsigned, VCC_UV_f ≤ VCC - VSS ≤ VL
12 bits, signed, VCC_UV_f ≤ VCC - VSS ≤ VL
OFFSET
OFFSET
OFFSET
OFFSET
1988
-60
1988
-60
2048
0
—
—
2108
+60
1988
-60
LSB
LSB
LSB
LSB
(1)
(1)
(3)
(3)
63a
64a
65a
66a
Offset at 0g (80g Range, No Offset Cancellation)
12 bits, unsigned
12 bits, signed
12 bits, unsigned, VCC_UV_f ≤ VCC - VSS ≤ VL
12 bits, signed, VCC_UV_f ≤ VCC - VSS ≤ VL
*
*
OFFSET
OFFSET
OFFSET
OFFSET
1968
-80
1968
-80
2048
0
—
—
2128
+80
1968
-80
LSB
LSB
LSB
LSB
(1)
(1)
(3)
(3)
67b
68b
69b
70b
Offset at 0g (With Offset Cancellation)
12 bits, unsigned
12 bits, signed
12 bits, unsigned, VCC_UV_f ≤ VCC - VSS ≤ VL
12 bits, signed, VCC_UV_f ≤ VCC - VSS ≤ VL
*
*
OFFSET
OFFSET
OFFSET
OFFSET
2047.75
-0.25
2047.75
-0.25
2048
0
—
—
2048.25
+0.25
2048.25
+0.25
LSB
LSB
LSB
LSB
(9,7)
(9,7)
(9)
(9)
OFFTHRPOS
OFFTHRNEG
—
—
100
-100
—
—
LSB
LSB
(7)
(7)
71
72
Offset Monitor Thresholds
Positive Threshold (12 bits signed)
Negative Threshold (12 bits signed)
73
74
75
76
Range of Output (SPI, 12 bits, unsigned)
Normal
Fault Response Code
Unused Codes
Unused Codes
RANGE
FAULT
UNUSED
UNUSED
128
—
1
3969
—
0
—
—
3968
—
127
4095
LSB
LSB
LSB
LSB
(7)
(7)
(7)
(7)
77
78
79
Range of Output (SPI, 12 bits, signed)
Normal
Unused Codes
Unused Codes
RANGE
UNUSED
UNUSED
-1920
-2047
1921
—
—
—
1920
-1921
2047
LSB
LSB
LSB
(7)
(7)
(7)
NLOUT
-1
—
1
% FSR
(3)
nRMS
nP-P
—
—
—
—
1
3
LSB
LSB
(3)
(3)
VZX
VYX
VZY
VXY
-4
-4
-4
-4
—
—
—
—
+4
+4
+4
+4
%
%
%
%
(3)
(3)
(3)
(3)
80 Nonlinearity
81
82
System Output Noise
RMS (12 bits, All Ranges, 400 Hz, 3-pole LPF)
Peak to Peak (12 bits, All Ranges, 400 Hz, 3-pole LPF)
83
84
85
86
Cross-Axis Sensitivity
VZX
VYX
VZY
VXY
*
*
*
*
*
MMA65xx
Sensor
Freescale Semiconductor, Inc.
7
2.5
Self Test
VL ≤ (VCC - VSS) ≤ VH, TL ≤ TA ≤ TH, |ΔTA| < 25 K/min unless otherwise specified.
#
Characteristic
87
88
89
90
91
92
93
94
95
Self Test Output Change (Ref Section 3.6)
80g, TA = 25°C
80g, -40°C ≤ TA ≤ 105°C
80g, -40°C ≤ TA ≤ 105°C, VCC_UV_f ≤ VCC - VSS ≤ VL
105.5g, TA = 25°C
105.5g, -40°C ≤ TA ≤ 105°C
105.5g, -40°C ≤ TA ≤ 105°C, VCC_UV_f ≤ VCC - VSS ≤ VL
120g, TA = 25°C
120g, -40°C ≤ TA ≤ 105°C
120g, -40°C ≤ TA ≤ 105°C, VCC_UV_f ≤ VCC - VSS ≤ VL
96
97
Self Test Cross-Axis Output
Y-Axis Output with X-Axis Self Test
X-Axis Output with Y-Axis Self Test
98
99
Self Test Output Accuracy
Δ from Stored Value, including Sensitivity Error
-40°C ≤ TA ≤ 105°C (Ref Section 3.6)
*
*
*
*
*
*
*
Symbol
Min
Typ
Max
Units
ΔST80_25
ΔST80_ΔT
ΔST80_ΔTΔV
ΔST105_25
ΔST105_ΔT
ΔST105_ΔTΔV
ΔST120_25
ΔST120_ΔT
ΔST120_ΔTΔV
ΔSTMIN
582
545
545
442
414
414
387
363
363
ΔSTNOM
727
727
727
553
553
553
484
484
484
ΔSTMAX
872
909
909
663
690
690
581
605
605
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
(1)
(1)
(3)
(1)
(1)
(3)
(1)
(1)
(3)
ΔSTCrossAxis
ΔSTCrossAxis
-10
-10
—
—
+10
+10
LSB
LSB
(1)
(1)
ΔSTACC
-10
—
+10
%
(3)
100
Sigma Delta Modulator Range
X/Y-Axis, Any Range Positive/Negative
gADCl_Clip
375
400
450
g
(19)
101
Acceleration (without hitting internal g-cell stops)
X/Y-Axis, Any Range Positive/Negative
gg-cell_Clip
500
560
600
g
(19)
MMA65xx
8
Sensor
Freescale Semiconductor, Inc.
2.6
Dynamic Electrical Characteristics - Signal Chain
VL ≤ (VCC - VSS) ≤ VH, TL ≤ TA ≤ TH, |ΔTA| < 25 K/min unless otherwise specified.
#
Characteristic
102
103
104
DSP Sample Rate (LPF 0,1,2,3,4,5)
DSP Sample Rate (LPF 8,9,10,11,12,13)
Interpolation Sample Rate
105
106
Data Path Latency (excluding g-cell and Low Pass Filter)
TS = 64/fOSC
TS = 128/fOSC
Symbol
Min
Typ
Max
Units
tS
tS
tINTERP
—
—
—
64/fOSC
128/fOSC
tS/2
—
—
—
s
s
s
(7)
(7)
(7)
*
*
tDataPath_8
tDataPath_16
33.0
51.9
34.8
54.6
36.5
57.4
μs
μs
(7,16)
(7,16)
*
*
*
*
*
*
fC0(LPF)
fC1(LPF)
fC2(LPF)
fC3(LPF)
fC4(LPF)
fC5(LPF)
95
285
380
760
950
380
100
300
400
800
1000
400
105
315
420
840
1050
420
Hz
Hz
Hz
Hz
Hz
Hz
(3,7,17)
(3,7,17)
(3,7,17)
(3,7,17)
(3,7,17)
(3,7,17)
*
*
*
*
*
*
fC8(LPF)
fC9(LPF)
fC10(LPF)
fC11(LPF)
fC12(LPF)
fC13(LPF)
47.5
142.5
190
380
475
190
50
150
200
400
500
200
52.5
157.5
210
420
525
210
Hz
Hz
Hz
Hz
Hz
Hz
(3,7,17)
(3,7,17)
(3,7,17)
(3,7,17)
(3,7,17)
(3,7,17)
*
*
*
*
*
*
*
OFFAVEPER
OFFSLEW
OFFRATE
OFFCORRP
OFFCORRN
OFFTHP
OFFTHN
—
—
—
—
—
—
—
6.29146
0.2384
1049
0.25
-0.25
0.125
0.125
—
—
—
—
—
—
—
s
LSB/s
ms
LSB
LSB
LSB
LSB
(3,7)
(3,7)
(3,7)
(3,7)
(3,7)
(3,7)
(3,7)
ST_ACT100
ST_ACT300
ST_ACT400
ST_ACT800
ST_ACT1000
ST_ACT400_3
—
—
—
—
—
—
—
—
—
—
—
—
7.00
3.00
2.50
1.70
1.60
2.40
ms
ms
ms
ms
ms
ms
(19)
(19)
(19)
(19)
(19)
(19)
Low-Pass Filter (ts = 8μs)
107
108
109
110
111
112
Cutoff frequency 0: 100 Hz, 4-pole
Cutoff frequency 1: 300 Hz, 4-pole
Cutoff frequency 2: 400 Hz, 4-pole
Cutoff frequency 3: 800 Hz, 4-pole
Cutoff frequency 4: 1000 Hz, 4-pole
Cutoff frequency 5: 400 Hz, 3-pole
Low-Pass Filter (ts = 16μs)
113
114
115
116
117
118
Cutoff frequency 8: 50 Hz, 4-pole
Cutoff frequency 9: 150 Hz, 4-pole
Cutoff frequency 10: 200 Hz, 4-pole
Cutoff frequency 11: 400 Hz, 4-pole
Cutoff frequency 12: 500 Hz, 4-pole
Cutoff frequency 13: 200 Hz, 3-pole
119
120
121
122
123
124
125
Offset Cancellation (Normal Mode, 12-Bit Output)
Offset Averaging Period
Offset Slew Rate
Offset Update Rate
Offset Correction Value per Update Positive
Offset Correction Value per Update Negative
Offset Correction Threshold Positive
Offset Correction Threshold Negative
126
127
128
129
130
131
Self Test Activation Time (CS rising edge to 90% of ST Final Value)
Cutoff frequency 0: 100 Hz, 4-pole
Cutoff frequency 1: 300 Hz, 4-pole
Cutoff frequency 2: 400 Hz, 4-pole
Cutoff frequency 3: 800 Hz, 4-pole
Cutoff frequency 4: 1000 Hz, 4-pole
Cutoff frequency 5: 400 Hz, 3-pole
132
Offset Monitor Bypass Time after Self Test Deactivation
tST_OMB
—
320
—
tS
(3,7)
133
Time Between Acceleration Data Requests (Same Axis)
tACC_REQ
15
—
—
μs
(3,7,20)
134
135
136
Arming Output Activation Time (ARM_X, ARM_Y, IARM = 200μA)
Moving Average and Count Arming Modes (2,3,4,5)
Unfiltered Mode Activation Delay (Reference Figure 30)
Unfiltered Mode Arm Assertion Time (Reference Figure 30)
tARM
tARM_UF_DLY
tARM_UF_ASSERT
0
0
5.00
—
—
—
1.51
1.51
6.579
μs
μs
μs
(3,12)
(3,12)
(3)
137
Sensing Element Natural Frequency
fgcell
10791
13464
15879
Hz
(19)
138
Sensing Element Cutoff Frequency (-3 dB ref. to 0 Hz)
fgcell
0.851
1.58
2.29
kHz
(19)
139
Sensing Element Damping Ratio
ζgcell
2.46
4.31
9.36
—
(19)
140
Sensing Element Delay (@100 Hz)
fgcell_delay
70
101
187
μs
(19)
141
Sensing Element Step Response (0% - 90%)
tStep_gcell
—
—
200
μs
(19)
142
Package Resonance Frequency
fPackage
100
—
—
kHz
(19)
143
Package Quality Factor
qPackage
1
—
5
(19)
MMA65xx
Sensor
Freescale Semiconductor, Inc.
9
2.7
Dynamic Electrical Characteristics - Supply and SPI
VL ≤ (VCC - VSS) ≤ VH, TL ≤ TA ≤ TH, |ΔTA| < 25 K/min unless otherwise specified
#
Characteristic
144
145
146
Power-On Recovery Time (VCC = VCCMIN to first SPI access)
Power-On Recovery Time (Internal POR to first SPI access)
SPI Reset Activation Time (CS high to Reset)
147
148
Internal Oscillator Frequency
Test Frequency - Divided from Internal Oscillator
149
Serial Interface Timing (See Figure 7, CMISO ≤ 80pF, RMISO ≥ 10kW)
Clock (SCLK) period (10% of VCC to 10% of VCC)
Symbol
Min
Typ
Max
Units
tOP
tOP
tSPI_RESET
—
—
—
—
—
—
10
840
300
ms
μs
ns
(3)
(3,7)
(7)
*
fOSC
fOSCTST
7.6
0.95
8
1
8.4
1.05
MHz
MHz
(7)
(1)
*
tSCLK
120
—
—
ns
(3)
150
Clock (SCLK) high time (90% of VCC to 90% of VCC)
*
tSCLKH
40
—
—
ns
(3)
151
Clock (SCLK) low time (10% of VCC to 10% of VCC)
*
tSCLKL
40
—
—
ns
(3)
152
Clock (SCLK) rise time (10% of VCC to 90% of VCC)
tSCLKR
—
15
40
ns
(19)
153
Clock (SCLK) fall time (90% of VCC to 10% of VCC)
tSCLKF
—
15
28
ns
(19)
154
CS asserted to SCLK high (CS = 10% of VCC to SCLK = 10% of VCC)
tLEAD
60
—
—
ns
(3)
155
CS asserted to MISO valid (CS = 10% of VCC to MISO = 10/90% of VCC)
tACCESS
—
—
60
ns
(3)
156
Data setup time (MOSI = 10/90% of VCC to SCLK = 10% of VCC)
*
tSETUP
20
—
—
ns
(3)
157
MOSI Data hold time (SCLK = 90% of VCC to MOSI = 10/90% of VCC)
*
tHOLD_IN
10
—
—
ns
(3)
158
MISO Data hold time (SCLK = 90% of VCC to MISO = 10/90% of VCC)
*
tHOLD_OUT
0
—
—
ns
(3)
159
SCLK low to data valid (SCLK = 10% of VCC to MISO = 10/90% of VCC)
*
tVALID
—
—
35
ns
(3)
160
SCLK low to CS high (SCLK = 10% of VCC to CS = 90% of VCC)
*
tLAG
60
—
—
ns
(3)
161
CS high to MISO disable (CS = 90% of VCC to MISO = Hi Z)
*
tDISABLE
—
—
60
ns
(3)
162
CS high to CS low (CS = 90% of VCC to CS = 90% of VCC)
*
tCSN
526
—
—
ns
(3)
163
SCLK low to CS low (SCLK = 10% of VCC to CS = 90% of VCC)
*
tCLKCS
50
—
—
ns
(3)
164
CS high to SCLK high (CS = 90% of VCC to SCLK = 90% of VCC)
tCSCLK
50
—
—
ns
(19)
1. Parameters tested 100% at final test.
2. Parameters tested 100% at wafer probe.
3. Parameters verified by characterization
4. (*) Indicates a critical characteristic.
5. Verified by qualification testing.
6. Parameters verified by pass/fail testing in production.
7. Functionality verified 100% via scan. Timing characteristic is directly determined by internal oscillator frequency.
8. N/A
9. Devices are trimmed at 100 Hz with 1000 Hz low-pass filter option selected. Response is corrected to 0 Hz response.
10.Low-pass filter cutoff frequencies shown are -3 dB referenced to 0 Hz response.
11.Power supply ripple at frequencies greater than 900 kHz should be minimized to the greatest extent possible.
12.Time from falling edge of CS to ARM_X, ARM_Y output valid
13.N/A
14.Thermal resistance between the die junction and the exposed pad; cold plate is attached to the exposed pad.
15.Device characterized at all values of VL & VH. Production test is conducted at all typical voltages (VTYP) unless otherwise noted.
16.Data Path Latency is the signal latency from g-cell to SPI output disregarding filter group delays.
17.Filter characteristics are specified independently, and do not include g-cell frequency response.
18.Electrostatic Deflection Test completed during wafer probe.
19.Verified by Simulation.
20.Acceleration Data Request timing constraint only applies for proper operation of the Arming Function
MMA65xx
10
Sensor
Freescale Semiconductor, Inc.
VCC_UV_r
VCC
VCC_UV_f
VREGA_UV_r
VREGA_UV_f
VREGA
Note: VREGA & VREG rise and fall slopes will be dependent
on output capacitance and load current
VREG_UVR_r
VREG_UVR_f
VREG
POR
DEVRES Flag Cleared by User
DEVRES
Time
Figure 6. Power-Up Timing
CS
tLEAD
tSCLKR
tSCLK
tSCLKF
tCSN
tSCLKH
tCSCLK
SCLK
tSCLKL
tLAG
tACCESS
tVALID
tHOLD_OUT
tCLKCS
tDISABLE
MISO
tHOLD_IN
tSETUP
MOSI
Figure 7. Serial Interface Timing
MMA65xx
Sensor
Freescale Semiconductor, Inc.
11
3
Functional Description
3.1
Customer Accessible Data Array
A customer accessible data array allows for each device to be customized. The array consists of an OTP factory programmable block and read/write registers for device programmability and status. The OTP and writable register blocks incorporate independent CRC circuitry for fault detection (reference Section 3.2). The writable register block includes a locking mechanism to
prevent unintended changes during normal operation. Portions of the array are reserved for factory-programmed trim values. The
customer accessible data is shown in the table below.
Table 3. Customer Accessible Data
Location
Bit Function
Type
Addr
Register
7
6
5
4
3
2
1
0
$00
SN0
SN[7]
SN[6]
SN[5]
SN[4]
SN[3]
SN[2]
SN[1]
SN[0]
$01
SN1
SN[15]
SN[14]
SN[13]
SN[12]
SN[11]
SN[10]
SN[9]
SN[8]
$02
SN2
SN[23]
SN[22]
SN[21]
SN[20]
SN[19]
SN[18]
SN[17]
SN[16]
$03
SN3
SN[31]
SN[30]
SN[29]
SN[28]
SN[27]
SN[26]
SN[25]
SN[24]
$04
STDEFL_X
STDEFL_X[7]
STDEFL_X[6]
STDEFL_X[5]
STDEFL_X[4]
STDEFL_X[3]
STDEFL_X[2]
STDEFL_X[1]
STDEFL_X[0]
$05
STDEFL_Y
STDEFL_Y[7]
STDEFL_Y[6]
STDEFL_Y[5]
STDEFL_Y[4]
STDEFL_Y[3]
STDEFL_Y[2]
STDEFL_Y[1]
STDEFL_Y[0]
$06
FCTCFG_X
1
0
0
0
0
0
0
1
$07
FCTCFG_Y
1
0
0
0
0
0
0
1
$08
PN
PN[7]
PN[6]
PN[5]
PN[4]
PN[3]
PN[2]
PN[1]
PN[0]
$0A
DEVCTL
RES_1
RES_0
OCPHASE[1]
OCPHASE[0]
OFFCFG_EN
Reserved
Reserved
Reserved
$0B
DEVCFG
OC
Reserved
ENDINIT
SD
OFMON
A_CFG[2]
A_CFG[1]
A_CFG[0]
$0C
DEVCFG_X
ST_X
Reserved
Reserved
Reserved
LPF_X[3]
LPF_X[2]
LPF_X[1]
LPF_X[0]
$0D
DEVCFG_Y
ST_Y
Reserved
Reserved
Reserved
LPF_Y[3]
LPF_Y[2]
LPF_Y[1]
LPF_Y[0]
$0E
ARMCFGX
Reserved
Reserved
APS_X[1]
APS_X[0]
AWS_XN[1]
AWS_XN[0]
AWS_XP[1]
AWS_XP[0]
$0F
ARMCFGY
Reserved
Reserved
APS_Y[1]
APS_Y[0]
AWS_YN[1]
AWS_YN[0]
AWS_YP[1]
AWS_YP[0]
$10
ARMT_XP
AT_XP[7]
AT_XP[6]
AT_XP[5]
AT_XP[4]
AT_XP[3]
AT_XP[2]
AT_XP[1]
AT_XP[0]
$09
F
Invalid Address: “Invalid Register Request”
R/W
$11
ARMT_YP
AT_YP[7]
AT_YP[6]
AT_YP[5]
AT_YP[4]
AT_YP[3]
AT_YP[2]
AT_YP[1]
AT_YP[0]
$12
ARMT_XN
AT_XN[7]
AT_XN[6]
AT_XN[5]
AT_XN[4]
AT_XN[3]
AT_XN[2]
AT_XN[1]
AT_XN[0]
$13
ARMT_YN
AT_YN[7]
AT_YN[6]
AT_YN[5]
AT_YN[4]
AT_YN[3]
AT_YN[2]
AT_YN[1]
AT_YN[0]
$14
DEVSTAT
UNUSED
IDE
UNUSED
DEVINIT
MISOERR
OFF_Y
OFF_X
DEVRES
$15
COUNT
COUNT[7]
COUNT[6]
COUNT[5]
COUNT[4]
COUNT[3]
COUNT[2]
COUNT[1]
COUNT[0]
$16
OFFCORR_X
OFFCORR_X[7]
OFFCORR_X[6]
OFFCORR_X[5]
OFFCORR_X[4]
OFFCORR_X[3]
OFFCORR_X[2]
OFFCORR_X[1]
OFFCORR_X[0]
$17
OFF_CORR_Y
OFFCORR_Y[7]
OFFCORR_Y[6]
OFFCORR_Y[5]
OFFCORR_Y[4]
OFFCORR_Y[3]
OFFCORR_Y[2]
OFFCORR_Y[1]
OFFCORR_Y[0]
$1C
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
$1D
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
R
Type codes
F: Factory programmed OTP location
R: Read-only register
R/W:
N/A:
Read/write register
Not applicable
MMA65xx
12
Sensor
Freescale Semiconductor, Inc.
3.1.1
Device Serial Number Registers
A unique serial number is programmed into the serial number registers of each device during manufacturing. The serial number is composed of the following information:
Bit Range
Content
S12 - S0
Serial Number
S31 - S13
Lot Number
Serial numbers begin at 1 for all produced devices in each lot, and are sequentially assigned. Lot numbers begin at 1 and are
sequentially assigned. No lot will contain more devices than can be uniquely identified by the 13-bit serial number. Depending on
lot size and quantities, all possible lot numbers and serial numbers may not be assigned.
The serial number registers are included in the OTP shadow register array CRC verification. Reference Section 3.2.1 for details regarding the CRC verification. Beyond this, the contents of the serial number registers have no impact on device operation
or performance, and are only used for traceability purposes.
3.1.2
Self Test Deflection Registers (STDEFL_X, STDEFL_Y)
These read-only registers provide the nominal self test deflection values for each axis at ambient temperature. The self test
value is a positive deflection value, measured at the factory, and factory programmed for each device. The minimum stored value
($00) equates to the minimum deflection specified in Section 2.4 (ΔSTMIN), and the maximum stored value ($FF) equates to the
maximum deflection specified in Section 2.4 (ΔSTMAX).
Table 4. Self Test Deflection Registers
Location
Bit
Address
Register
7
6
5
4
3
2
1
0
$04
STDEFL_X
STDEFL_X[7]
STDEFL_X[6]
STDEFL_X[5]
STDEFL_X[4]
STDEFL_X[3]
STDEFL_X[2]
STDEFL_X[1]
STDEFL_X[0]
$05
STDEFL_Y
STDEFL_Y[7]
STDEFL_Y[6]
STDEFL_Y[5]
STDEFL_Y[4]
STDEFL_Y[3]
STDEFL_Y[2]
STDEFL_Y[1]
STDEFL_Y[0]
When self test is activated, the acceleration reading can be compared to the value in this register. The difference from the
measured deflection value, and the nominal deflection value stored in the register shall not fall outside the self test accuracy limits
specified in Section 2.4 (ΔSTACC). Reference Section 3.6 for more details on calculating the self test limits.
3.1.3
Factory Configuration Registers
The factory configuration registers are one time programmable, read only registers which contain customer specific device
configuration information that is programmed by Freescale.
Table 5. Factory Configuration Register
Location
Bit
Address
Register
7
6
5
4
3
2
1
0
$06
FCTCFG_X
1
0
0
0
0
0
0
1
$07
FCTCFG_Y
1
0
0
0
0
0
0
1
MMA65xx
Sensor
Freescale Semiconductor, Inc.
13
3.1.4
Part Number Register (PN)
The part number register is a one time programmable, read only register which contains two digits of the device part number
to identify the axis and range information. The contents of this register have no impact on device operation or performance.
Table 6. Part Number Register
Location
Bit
Address
Register
7
6
5
4
3
2
1
0
$08
PN
PN[7]
PN[6]
PN[5]
PN[4]
PN[3]
PN[2]
PN[1]
PN[0]
PN Register Value
3.1.5
Decimal
HEX
X-Axis Range
Section 2.4
Y-Axis Range
Section 2.4
219
$DB
80
80
225
$E1
105
105
227
$E3
120
120
Device Control Register (DEVCTL
The device control register is a read-write register which contains device control operations. The upper 2 bits of this register
can be written during both initialization and normal operation. Bits 5 through 0 can be programmed during initialization and then
are ignored once the ENDINIT bit is set.
Table 7. Device Control Register
Location
Bit
Address
Register
7
6
$0A
DEVCTL
RES_1
RES_0
0
0
Reset Value
5
4
3
OCPHASE[1] OCPHASE[0] OFFCFG_EN
0
0
0
2
1
0
Reserved
Reserved
Reserved
0
0
0
3.1.5.1
Reset Control (RES_1, RES_0)
A series of three consecutive register write operations to the reset control bits in the DEVCTL register will cause a device reset.
To reset the internal digital circuitry, the following register write operations must be performed in the order shown below. The register write operations must be consecutive SPI commands in the order shown or the device will not be reset.
Register Write to DEVCTL
RES_1
RES_0
Effect
SPI Register Write 1
0
0
No Effect
SPI Register Write 2
1
1
No Effect
SPI Register Write 3
0
1
Device RESET
The response to the Register Write returns ‘0’ for RES_1 and RES_0, and the existing register value bits 5 through 0. A Register Read of RES_1 and RES_0 returns ‘0’ and terminates the reset sequence. If ENDINIT is cleared, the bits 2 through 0 in the
DEVCTL register are modified as described in Section 4.4. If ENDINIT is set, a Register Write will not modify bits 2 through 0 and
the response to a Register Read or Write will include the last successful written values for these bits.
MMA65xx
14
Sensor
Freescale Semiconductor, Inc.
3.1.5.2
Offset Cancellation Phase Control Bits (OCPHASE[1:0])
The offset cancellation phase control bits control the offset cancellation start up phase. These bits can be written at any time
ENDINIT is ‘0’ if the OFFCFG_EN bit is set.
OFFCFG_EN
OCPHASE[1]
OCPHASE[0]
Writes to
OCPHASE[1:0]
Offset Cancellation Phase
0
Don’t Care
Don’t Care
Ignored
Continues from the previously written phase (OCPHASE[1:0]) as
specified in Section 3.8.4.
1
0
0
Accepted
Remains in Start 1 until OFFCFG_EN is cleared or ENDINIT is set
1
0
1
Accepted
Remains in Start 2 until OFFCFG_EN is cleared or ENDINIT is set
1
1
0
Accepted
Remains in Start 3 until OFFCFG_EN is cleared or ENDINIT is set
1
1
1
Accepted
Remains in Normal Mode until OFFCFG_EN is cleared or ENDINIT is set
When ENDINIT is set, the OCPHASE[1:0] bits in a write command are ignored and the offset cancellation phase is set to “Normal”. This can only be changed by a device reset. The response to a register read or write of the DEVCTL register once ENDINIT
is set will return the last successfully written values of OCPHASE[1:0].
3.1.5.3
Offset Cancellation Configuration Enable Bit (OFFCFG_EN)
The offset cancellation phase configuration enable bit enables modification of the offset cancellation phase control bits
(OCPHASE[1:0]) as shown in Section 3.1.5.2
When ENDINIT is set, the OFFCFG_EN bit in a write command is ignored, and the offset cancellation phase is set to “Normal”.
This can only be changed by a device reset. The response to a register read or write of the DEVCTL register once ENDINIT is
set will return the last successfully written value of OFFCFG_EN.
3.1.5.4
Reserved Bits (DEVCTL[2:0])
Bits 2 through 0 of the DEVCTL register are reserved. A write to the reserved bits must always be logic ‘0’ for normal device
operation and performance.
3.1.6
Device Configuration Register (DEVCFG)
The device configuration register is a read/write register which contains data for general device configuration. The register can
be written during initialization but is locked once the ENDINIT bit is set. This register is included in the writable register CRC
check. Refer to Section 3.2.2 for details.
Table 8. Device Configuration Register
Location
Bit
Address
Register
7
6
5
4
3
2
1
0
$0B
DEVCFG
OC
Reserved
ENDINIT
SD
OFMON
A_CFG[2]
A_CFG[1]
A_CFG[0]
0
0
0
0
0
0
0
0
Reset Value
3.1.6.1
Offset Cancelled Data Selection Bits (OC)
The Offset Cancelled Data Selection Bit determines whether the SPI transmitted data is raw data or offset cancelled data.
OC
SPI Data
0
Offset Cancelled
1
Raw Data
If the OC bit is cleared (Offset Cancelled Data), then the Offset Monitor is automatically enabled (OFMON = ‘1’) regardless of
the value written to DEVCFG[3].
3.1.6.2
Reserved Bit (Reserved)
Bits 6 of the DEVCFG register is reserved. A write to the reserved bit must always be logic ‘0’ for normal device operation and
performance.
MMA65xx
Sensor
Freescale Semiconductor, Inc.
15
3.1.6.3
End of Initialization Bit (ENDINIT)
The ENDINIT bit is a control bit used to indicate that the user has completed all device and system level initialization tests,
and that the device will operate in normal mode. Once the ENDINIT bit is set, writes to all writable register bits are inhibited except
for the DEVCTL register. Once written, the ENDINIT bit can only be cleared by a device reset. The writable register CRC check
(reference Section 3.2.2) is only enabled when the ENDINIT bit is set.
When ENDINIT is set, the following occurs:
• Offset Cancellation is forced to normal mode. OCPHASE[1:0], and OFFCFG_EN remain in their previously set states.
• X-Axis Self Test is disabled. ST_X remains in its previously set states.
• Y-Axis Self Test is disabled. ST_Y remains in its previously set states.
3.1.6.4
SD Bit
The SD bit determines the format of acceleration data results. If the SD bit is set to a logic ‘1’, unsigned results are transmitted,
with the zero-g level represented by a nominal value of 512. If the SD bit is cleared, signed results are transmitted, with the zerog level represented by a nominal value of 0.
SD
Operating Mode
1
Unsigned Data Output
0
Signed Data Output
3.1.6.5
OFMON Bit
The OFMON bit determines if the offset monitor circuit is enabled. If the OFMON bit is set to a logic ‘1’, the offset monitor is
enabled. Reference Section 3.8.5. If the OFMON bit is cleared, the offset monitor is disabled.
OFMON
Operating Mode
1
Offset Monitor Circuit Enabled
0
Offset Monitor Circuit Disabled
If the OC bit in the DEVCFG register is cleared (Offset Cancelled Data), then the Offset Monitor is automatically enabled (OFMON = ‘1’) regardless of the value written to DEVCFG[3].
3.1.6.6
ARM Configuration Bits (A_CFG[2:0])
The ARM Configuration Bits (A_CFG[2:0]) select the mode of operation for the ARM_X/PCM_X, ARM_Y/PCM_Y pins.
Table 9. Arming Output Configuration
A_CFG[2]
A_CFG[1]
A-CFG[0]
Operating Mode
Output Type
Reference
0
0
0
Arm Output Disabled
Hi Impedance
0
0
1
PCM Output
Digital Output
Section 3.8.11
0
1
0
Moving Average Mode
Active High with Pulldown Current
Section 3.8.10.1
0
1
1
Moving Average Mode
Active Low with Pullup Current
Section 3.8.10.1
1
0
0
Count Mode
Active High with Pulldown Current
Section 3.8.10.2
1
0
1
Count Mode
Active Low with Pullup Current
Section 3.8.10.2
1
1
0
Unfiltered Mode
Active High with Pulldown Current
Section 3.8.10.3
1
1
1
Unfiltered Mode
Active Low with Pullup Current
Section 3.8.10.3
MMA65xx
16
Sensor
Freescale Semiconductor, Inc.
3.1.7
Axis Configuration Registers (DEVCFG_X, DEVCFG_Y)
The Axis configuration registers are read/write registers which contain axis specific configuration information. These registers
can be written during initialization, but are locked once the ENDINIT bit is set. These registers are included in the writable register
CRC check. Refer to Section 3.2.2 for details.
Table 10. Axis Configuration Registers
Location
Bit
Address
Register
7
6
5
4
3
2
1
0
$0C
DEVCFG_X
ST_X
Reserved
Reserved
Reserved
LPF_X[3]
LPF_X[2]
LPF_X[1]
LPF_X[0]
$0D
DEVCFG_Y
ST_Y
Reserved
Reserved
Reserved
LPF_Y[3]
LPF_Y[2]
LPF_Y[1]
LPF_Y[0]
0
0
0
0
0
0
0
0
Reset Value
3.1.7.1
Self Test Control (ST_X, ST_Y)
The ST_X and ST_Y bits enable and disable the self test circuitry for their respective axes. Self test circuitry is enabled if a
logic ‘1’ is written to ST_X, or ST_Y and the ENDINIT bit has not been set. Enabling the self test circuitry results in a positive
acceleration value on the enabled axis. Self test deflection values are specified in Section 2.4. ST_X and ST_Y are always
cleared following internal reset.
When the self test circuitry is active, the offset cancellation block and the offset monitor status are suspended, and the status
bits in the Acceleration Data Request Response will indicate “Self Test Active”. Reference Section 3.8.4 and Section 4.2 for details. When the self test circuitry is disabled by clearing the ST_X or ST_Y bit, the offset monitor remains disabled until the time
tST_OMB specified in Section 2.6 expires. However, the status bits in the Acceleration Data Request Response will immediately
indicate that self test is deactivated.
When ENDINIT is set, self test is disabled. This can only be changed by a reset. A Register Write will not modify the ST_X
and ST_Y bits and the response to a Register Read or Write will include the last successful written values for these bits.
3.1.7.2
Reserved Bits (Reserved)
Bits 6 through 4 of the DEVCFG_X and DEVCFG_Y registers are reserved. A write to the reserved bits must always be logic
‘0’ for normal device operation and performance.
3.1.7.3
Low-Pass Filter Selection Bits (LPF_X[3:0], LPF_Y[3:0])
The Low Pass Filter selection bits independently select a low-pass filter for each axis as shown in Table 11. Refer to
Section 3.8.3 for details regarding filter configurations.
Table 11. Low Pass Filter Selection Bits
LPF_X[3] /
LPF_Y[3]
LPF_X[2] /
LPF_Y[2]
LPF_X[1] /
LPF_Y[1]
LPF_X[0] /
LPF_Y[0]
Low Pass Filter Selected
Nominal Sample Rate (μs)
0
0
0
0
100 Hz, 4-pole
8
0
0
0
1
300 Hz, 4-pole
8
0
0
1
0
400 Hz, 4-pole
8
0
0
1
1
800 Hz, 4-pole
8
0
1
0
0
1000 Hz, 4-pole
8
0
1
0
1
400 Hz, 3-pole
8
0
1
1
0
Reserved
Reserved
0
1
1
1
Reserved
Reserved
1
0
0
0
50 Hz, 4-pole
16
1
0
0
1
150 Hz, 4-pole
16
1
0
1
0
200 Hz, 4-pole
16
1
0
1
1
400 Hz, 4-pole
16
1
1
0
0
500 Hz, 4-pole
16
1
1
0
1
200 Hz, 3-pole
16
1
1
1
0
Reserved
Reserved
1
1
1
1
Reserved
Reserved
Note:Filter characteristics do not include g-cell frequency response.
MMA65xx
Sensor
Freescale Semiconductor, Inc.
17
3.1.8
Arming Configuration Registers (ARMCFGX, ARMCFGY)
The arming configuration registers contain configuration information for the arming function. The values in these registers are
only relevant if the arming function is operating in moving average mode, or count mode.
These registers can be written during initialization but are locked once the ENDINIT bit is set. Refer to Section 3.1.6.3. These
registers are included in the writable register CRC check. Refer to Section 3.2.2 for details.
Table 12. Arming Configuration Register
Location
Bit
Address
Register
7
6
5
4
$0E
ARMCFGX
Reserved
Reserved
APS_X[1]
APS_X[0]
$0F
ARMCFGY
Reserved
Reserved
APS_Y[1]
APS_Y[0]
0
0
0
0
Reset Value
3.1.9
3
2
1
0
AWS_XN[1] AWS_XN[0]
AWS_XP[1]
AWS_XP[0]
AWS_YN[1] AWS_YN[0]
AWS_YP[1]
AWS_YP[0]
1
1
1
1
Reserved Bits (Reserved)
Bits 7 through 6 of the ARMCFGX and ARMCFGY registers are reserved. A write to the reserved bits must always be logic ‘0’
for normal device operation and performance.
3.1.9.1
Arming Pulse Stretch (APS_X[1:0], APS_Y[1:0])
The APS_X[1:0] and APS_Y[1:0] bits set the programmable pulse stretch time for the arming outputs. Refer to Section 3.8.10
for more details regarding the arming function. Pulse stretch times are derived from the internal oscillator, so the tolerance on
this oscillator applies.
Table 13. Arming Pulse Stretch Definitions
APS_X[1], APS_Y[1]
APS_X[0], APS_Y[0]
Pulse Stretch Time (Typical Oscillator)
0
0
0 mS
0
1
16.256 ms - 16.384 ms
1
0
65.408ms - 65.536 ms
1
1
261.888ms - 262.016 ms
3.1.9.2
Arming Window Size (AWS_Xx[1:0], AWS_Yx[1:0])
The AWS_Xx[1:0] & AWS_Yx[1:0] bits have different functions depending on the state of the A_CFG bits in the DEVCFG register. If the arming function is set to moving average mode, the AWS bits set the number of acceleration samples used for the
arming function moving average. The number of samples is set independently for each axis and polarity. If the arming function
is set to count mode, the AWS bits set the sample count limit for the arming function. The sample count limit is set independently
for each axis. Refer to Section 3.8.10 for more details regarding the arming function.
Table 14. X-Axis Positive Arming Window Size Definitions (Moving Average Mode)
AWS_XP[1]
AWS_XP[0]
X-Axis Positive Window Size
0
0
2
0
1
4
1
0
8
1
1
16
Table 15. X-Axis Negative Arming Window Size Definitions (Moving Average Mode)
AWS_XN[1]
AWS_XN[0]
X-Axis Negative Window Size
0
0
2
0
1
4
1
0
8
1
1
16
MMA65xx
18
Sensor
Freescale Semiconductor, Inc.
Table 16. Y-Axis Positive Arming Window Size Definitions (Moving Average Mode)
AWS_YP[1]
AWS_YP[0]
Y-Axis Positive Window Size
0
0
2
0
1
4
1
0
8
1
1
16
Table 17. Y-Axis Negative Arming Window Size Definitions (Moving Average Mode)
AWS_YN[1]
AWS_YN[0]
Y-Axis Negative Window Size
0
0
2
0
1
4
1
0
8
1
1
16
Table 18. Arming Count Limit Definitions (Count Mode)
AWS_XN[1]
AWS_XN[0]
AWS_XP[1]
AWS_XP[0]
X-Axis Sample Count Limit
Don’t Care
Don’t Care
0
0
1
Don’t Care
Don’t Care
0
1
3
Don’t Care
Don’t Care
1
0
7
Don’t Care
Don’t Care
1
1
15
Table 19. Arming Count Limit Definitions (Count Mode)
3.1.10
AWS_YN[1]
AWS_YN[0]
AWS_YP[1]
AWS_YP[0]
Y-Axis Sample Count Limit
Don’t Care
Don’t Care
0
0
1
Don’t Care
Don’t Care
0
1
3
Don’t Care
Don’t Care
1
0
7
Don’t Care
Don’t Care
1
1
15
Arming Threshold Registers (ARMT_XP, ARMT_XN, ARMT_YP, ARMT_YN)
The arming threshold registers contain the X-axis and Y-axis positive and negative thresholds to be used by the arming function. Refer to Section 3.8.10 for more details regarding the arming function.
The arming threshold registers can be written during initialization but are locked once the ENDINIT bit is set. Refer to
Section 3.1.6.3. The arming threshold registers are included in the writable register CRC check. Refer to Section 3.2.2 for details.
Table 20. Arming Threshold Registers
Location
Bit
Address
Register
7
6
5
4
3
2
1
0
$10
ARMT_XP
AT_XP[7]
AT_XP[6]
AT_XP[5]
AT_XP[4]
AT_XP[3]
AT_XP[2]
AT_XP[1]
AT_XP[0]
$11
ARMT_YP
AT_YP[7]
AT_YP[6]
AT_YP[5]
AT_YP[4]
AT_YP[3]
AT_YP[2]
AT_YP[1]
AT_YP[0]
$12
ARMT_XN
AT_XN[7]
AT_XN[6]
AT_XN[5]
AT_XN[4]
AT_XN[3]
AT_XN[2]
AT_XN[1]
AT_XN[0]
$13
ARMT_YN
AT_YN[7]
AT_YN[6]
AT_YN[5]
AT_YN[4]
AT_YN[3]
AT_YN[2]
AT_YN[1]
AT_YN[0]
0
0
0
0
0
0
0
0
Reset Value
MMA65xx
Sensor
Freescale Semiconductor, Inc.
19
The values programmed into the threshold registers are the threshold values used for the arming function as described in
Section 3.8.10. The threshold registers hold independent unsigned 8-bit values for each axis and polarity. Each threshold increment is equivalent to one output LSB. Table 21 shows examples of some threshold register values and the corresponding threshold.
Table 21. Threshold Register Value Examples
Axis Type
Programmed Thresholds
Positive Threshold
(g)
Negative Threshold
(g)
50
4.17
-2.08
255
0
10.625
Disabled
24
50
20
2.08
-0.83
80
24
150
75
6.25
-3.125
105.5
18.2
100
50
5.50
-2.75
105.5
18.2
255
0
14.0
Disabled
105.5
18.2
50
20
2.75
-1.10
105.5
18.2
150
75
8.24
-4.12
Range
(g)
Sensitivity
(LSB/g)
Positive
(Decimal)
Negative
(Decimal)
80
24
100
80
24
80
If either the positive or negative threshold for one axis is programmed to $00, comparisons are disabled for only that polarity.
The arming function still operates for the opposite polarity. If both the positive and negative arming thresholds for one axis are
programmed to $00, the Arming function for the associated axis is disabled, and the associated output pin is disabled, regardless
of the value of the A_CFG bits in the DEVCFG register.
3.1.11
Device Status Register (DEVSTAT)
The device status register is a read-only register. A read of this register clears the status flags affected by transient conditions.
Reference Section 4.5 for details on the response for each status condition.
Table 22. Device Status Register
Location
Bit
Address
Register
7
6
5
4
3
2
1
0
$14
DEVSTAT
UNUSED
IDE
UNUSED
DEVINIT
MISOERR
OFF_Y
OFF_X
DEVRES
3.1.11.1
Unused Bits (UNUSED)
The unused bits have no impact on operation or performance. When read these bits may be ‘1’ or ‘0’.
3.1.11.2
Internal Data Error Flag (IDE)
The internal data error flag is set if a customer or OTP register data CRC fault or other internal fault is detected as defined in
Section 4.5.5. The internal data error flag is cleared by a read of the DEVSTAT register. If the error is associated with a CRC fault
in the writable register array, the fault will be re-asserted and will require a device reset to clear. If the error is associated with the
data stored in the fuse array, the fault will be re-asserted even after a device reset.
3.1.11.3
Device Initialization Flag (DEVINIT)
The device initialization flag is set during the interval between negation of internal reset and completion of internal device initialization. DEVINIT is cleared automatically. The device initialization flag is not affected by a read of the DEVSTAT register.
3.1.11.4
SPI MISO Data Mismatch Error Flag (MISOERR)
The MISO data mismatch flag is set when a MISO Data mismatch fault occurs as specified in Section 4.5.2. The MISOERR
flag is cleared by a read of the DEVSTAT register.
3.1.11.5
Offset Monitor Error Flags (OFF_X, OFFSET_Y)
The offset monitor error flags are set if the acceleration signal of the associated axis reaches the specified offset limit. The
offset monitor error flags are cleared by a read of the DEVSTAT register.
3.1.11.6
Device Reset Flag (DEVRES)
The device reset flag is set during device initialization following a device reset. The device reset flag is cleared by a read of
the DEVSTAT register.
MMA65xx
20
Sensor
Freescale Semiconductor, Inc.
3.1.12
Count Register (COUNT)
The count register is a read-only register which provides the current value of a free-running 8-bit counter derived from the primary oscillator. A 10-bit pre-scaler divides the primary oscillator frequency by 1024. Thus, the value in the register increases by
one count every 128 μs and the counter rolls over every 32.768 ms.
Table 23. Count Register
Location
Bit
Address
Register
7
6
5
4
3
2
1
0
$15
COUNT
COUNT[7]
COUNT[6]
COUNT[5]
COUNT[4]
COUNT[3]
COUNT[2]
COUNT[1]
COUNT[0]
0
0
0
0
0
0
0
0
Reset Value
3.1.13
Offset Correction Value Registers (OFFCORR_X, OFFCORR_Y)
The offset correction value registers are read-only registers which contain the most recent offset correction increment / decrement value from the offset cancellation circuit. The values stored in these registers indicate the amount of offset correction being applied to the SPI output data. The values have a resolution of 1 LSB.
Table 24. Offset Correction Value Register
Location
Address
Bit
Register
7
6
5
4
3
2
1
0
$16
OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_
X
X[7]
X[6]
X[5]
X[4]
X[3]
X[2]
X[1]
X[0]
$17
OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_ OFFCORR_
Y
Y[7]
Y[6]
Y[5]
Y[4]
Y[3]
Y[2]
Y[1]
Y[0]
Reset Value
3.1.14
0
0
0
0
0
0
0
0
Reserved Registers (Reserved)
Registers $1C and $1D are reserved. A write to the reserved bits must always be logic ‘0’ for normal device operation and
performance.
Table 25. Reserved Registers
Location
Bit
Address
Register
7
6
5
4
3
2
1
0
$1C
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
$1D
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
0
0
0
0
0
0
0
0
Reset Value
3.2
Customer Accessible Data Array CRC Verification
3.2.1
OTP Shadow Register Array CRC Verification
The OTP shadow register array is verified for errors using a 3-bit CRC. The CRC verification uses a generator polynomial of
g(x) = X3 + X + 1, with a seed value = ‘111’. If a CRC error is detected in the OTP array, the IDE bit is set in the DEVSTAT register.
3.2.2
Writable Register CRC Verification
The writable registers in the data array are verified for errors using a 3-bit CRC. The CRC verification is enabled only when
the ENDINIT bit is set in the DEVCFG register. The CRC verification uses a generator polynomial of g(x) = X3+X+1, with a seed
value = ‘111’. If a CRC error is detected in the writable register array, the IDE bit is set in the DEVSTAT register.
MMA65xx
Sensor
Freescale Semiconductor, Inc.
21
3.3
Voltage Regulators
Separate internal voltage regulators supply the analog and digital circuitry. External filter capacitors are required, as shown in
Figure 1. The voltage regulator module includes voltage monitoring circuitry which indicates a device reset until the external supply and all internal regulated voltages are within predetermined limits. A reference generator provides a stable voltage which is
used by the ΣΔ converters.
VCC
BANDGAP
REFERENCE
VREGA = 2.50 V
VOLTAGE
REGULATOR
VREGA
PRIMARY
OSCILLATOR
BIAS
GENERATOR
TRIM
TRIM
ΣΔ
CONVERTER
REFERENCE
GENERATOR
VREF = 1.250 V
DIGITAL
LOGIC
DSP
TRACKING
REGULATOR
Tracks VREGA
OTP
ARRAY
VREG = 2.50 V
VREG
Figure 8. Power Supply Block Diagram
VCCUV
VCC
VREG
VREGOV
VREGUV
MONITOR
BANDGAP
GROUND LOSS
MONITOR
VBGMON
VREGA
SET DEVRES Flag
VREGAUV
VREGAOV
VREG
VREF
VREFOV
VREFUV
VPORREF
POR
Note: No external access to reference voltage
Limits verified by characterization only
Figure 9. Voltage Monitoring
MMA65xx
22
Sensor
Freescale Semiconductor, Inc.
3.3.1
CVREG Failure Detection
The digital supply voltage regulator is designed to be unstable with low capacitance. If the connection to the VREG capacitor
becomes open, the digital supply voltage will oscillate and cause either an under voltage, or over voltage failure within one internal sample time. This failure will result in one of the following:
1. The DEVRES flag in the DEVSTAT register will be set. The device will respond to SPI acceleration requests as defined
in Table 30.
2. The device will be held in RESET and be non-responsive to SPI requests.
3.3.2
CVREGA Failure Detection
The analog supply voltage regulator is designed to be unstable with low capacitance. If the connection to the VREGA capacitor
becomes open, the analog supply voltage will oscillate and cause either an under voltage, or over voltage failure within one internal sample time. The DEVRES flag in the DEVSTAT register will be set. The device will respond to SPI acceleration requests
as defined in Table 30.
3.3.3
VSS and VSSA Ground Loss Monitor
The device detects the loss of ground connection to either VSS or VSSA. A loss of ground connection to VSS will result in a
VREG overvoltage failure. A loss of ground connection to VSSA will result in a VREG undervoltage failure. Both failures result in a
device reset.
3.3.4
SPI Initiated Reset
In addition to voltage monitoring, a device reset can be initiated by a specific series of three write operations involving the
RES_1 and RES_0 bits in the DEVCTL register. Reference Section 3.1.5.1. for details regarding the SPI initiated reset.
3.4
Internal Oscillator
The device includes a factory trimmed oscillator as specified in Section 2.7.
3.4.1
Oscillator Monitor
The COUNT register in the customer accessible array is a read-only register which provides the current value of a free-running
8-bit counter derived from the primary oscillator. A 10-bit pre-scaler divides the primary oscillator by 1024. Thus, the value in the
COUNT register increases by one count every 128 μs, and the register rolls over every 32.768 ms. The SPI master can periodically read the COUNT register, and verify the difference between subsequent register reads against the system time base.
1. The SPI access rates and deviations must be taken into account for this oscillator verification method.
3.4.2
CRC Based Clock Monitor
The device includes unique DSP cores for the X-Axis and Y-Axis. Each DSP core uses multiple frequencies derived from the
oscillator, ranging from the base oscillator frequency to the base oscillator frequency divided by 256. In order to guarantee that
the clocks for the two DSP cores are synchronized, a clock CRC monitor is employed. The CRC monitor is updated every cycle
of the base oscillator.
3.5
Transducer
The transducer is an overdamped mass-spring-damper system described by the following transfer function:
2
ωn
H ( s ) = -----------------------------------------------------2
2
s + 2 ⋅ ξ ⋅ ωn ⋅ s + ωn
where:
ζ= Damping Ratio
ωn= Natural Frequency = 2∗Π∗fn
Reference Section 2.4 for transducer parameters.
MMA65xx
Sensor
Freescale Semiconductor, Inc.
23
3.6
Self Test Interface
When self test is enabled, the self test interface applies a voltage to the g-cell, causing a deflection of the proof mass. Once
enabled, offset cancellation is suspended and the deflection results in an acceleration which is superimposed upon the input acceleration.
The resulting acceleration readings can be compared either against absolute limits, or the values stored in the Self Test Deflection Registers (Reference Section 3.1.2). The self test interface is controlled through SPI write operations to the DEVCFG_X
and DEVCFG_Y registers described in Section 3.1.7 only if the ENDINIT bit in the DEVCFG register is cleared. A diagram of the
self test interface is shown in Figure 10.
ST_Y
ENDINIT
Y-AXIS
g-CELL
SELF TEST
VOLTAGE
GENERATOR
ENDINIT
X-AXIS
g-CELL
ENDINIT
ST_X
Figure 10. Self Test Interface
3.6.1
Raw Self Test Deflection Verification
The raw self test deflection can be directly verified against raw self test limits listed in Section 2.4.
3.6.2
Delta Self Test Deflection Verification
The raw self test deflection can be verified against the ambient temperature self test deflection value recorded at the time the
device was produced. The production self test deflection is stored in the STDEFL_X and STDDEFL_Y registers such that the
minimum stored value (0x00) is equivalent to ΔSTMIN, and the maximum stored value (0xFF) is equivalent to ΔSTMAX. The Delta
Self Test Deflection limits can then be determined by the following equations:
ΔSTDEFLx CNTS
ΔST ACCMINLIMIT = FLOOR ⋅ ⎛⎝ ΔST MIN + ------------------------------------------ × [ ΔST MAX – ΔST MIN ]⎞⎠ × ( 1 – ΔST ACC )
255
ΔSTDEFLx CNTS
ΔST ACCMAXLIMIT = CEIL ⋅ ⎛⎝ ΔST MIN + ------------------------------------------ × [ ΔST MAX – ΔST MIN ]⎞⎠ × ( 1 + ΔST ACC )
255
where:
ΔSTACC
ΔSTDEFLxCNTS
The accuracy of the self test deflection relative to the stored deflection as specified in Section 2.4.
The value stored in the STDEFL_X or STDEFL_Y register.
ΔSTMIN
The minimum self test deflection at 25C as specified in Section 2.4.
ΔSTMAX
The maximum self test deflection at 25C as specified in Section 2.4.
MMA65xx
24
Sensor
Freescale Semiconductor, Inc.
ΣΔ Converter
3.7
A sigma delta converter provides the interface between the transducer and the DSP. The output of the ΣΔ converter is a data
stream at a nominal frequency of 1 MHz.
g-CELL
α1=
CTOP
VX
FIRST
INTEGRATOR
CINT1
z-1
SECOND
INTEGRATOR
α2
z-1
1 - z-1
CBOT
1-BIT
QUANTIZER
ΣΔ_OUT
1 - z-1
ADC
ΔC = CTOP - CBOT
β1
β2
V = ΔC x VX / CINT1
V = ±2 × VREF
DAC
Figure 11. ΣΔ Converter Block Diagram
3.8
Digital Signal Processing Block
A digital signal processing (DSP) block is used to perform signal filtering and compensation operations. A diagram illustrating
the signal processing flow is shown in Figure 12.
Arm/PCM Output
Section 3.8.9
Section 3.8.10
A
ΣΔ_OUT
SINC Filter
Section 3.8.2
B
Low Pass Filter
Section 3.8.3
C Compensation D
Section 3.8.6
Interpolation
Section 3.8.7
E
Offset Cancellation
Section 3.8.4
F
Offset Cancellation
Output Scaling
Raw Output
Scaling
I
To ARM_x
G
To SPI
H
To SPI
Figure 12. Signal Chain Diagram
Table 26. Signal Chain Characteristics
Description
Sample Data Width Over Range
Time (μs)
Bits
Bits
Effective
Bits
Rounding
Resolution Bits
Typical Block
Latency
Reference
A
SD
1
1
1
3.2μs
Section 3.7
B
SINC Filter
8
14
13
11.2μs
Section 3.8.2
C
Low Pass Filter
8/16
20
4
12
4
Reference
Section 3.8.3
Section 3.8.3
D
Compensation
8/16
20
4
12
4
7.875μs
Section 3.8.6
E
Interpolation
4/8
20
4
12
4
ts / 2
Section 3.8.8
F
Offset
Cancellation
256
20
4
12
4
N/A
Section 3.8.4
GH
SPI Output
4/8
—
—
12
—
ts / 2
I
PCM Output
4/8
—
—
9
—
Section 3.8.11
MMA65xx
Sensor
Freescale Semiconductor, Inc.
25
3.8.1
DSP Clock
The DSP is clocked at 8 MHz, with an effective 6MHz operating frequency. The clock to the DSP is disabled for 1 clock prior
to each edge of the ΣΔ modulator clock to minimize noise during data conversion.
8 MHz OSC
6 MHz Digital
1MHz Modulator
Figure 13. Clock Generation
3.8.2
Decimation Sinc Filter
The serial data stream produced by the ΣΔ converter is decimated and converted to parallel values by a 3rd order 16:1 sinc
filter with a decimation factor of 8 or 16, depending on the Low Pass Filter selected.
3
1 – z – 16
H ( z ) = ----------------------------------16 × ( 1 – z – 1 )
Figure 14. Sinc Filter Response, tS = 8 μs
3.8.3
Low Pass Filter
Data from the Sinc filter is processed by an infinite impulse response (IIR) low pass filter.
.
n0 + ( n1 ⋅ z –1 ) + ( n2 ⋅ z –2 ) + ( n3 ⋅ z –3 ) + ( n4 ⋅ z –4 )
H ( z ) = --------------------------------------------------------------------------------------------------------------------------------d0 + ( d1 ⋅ z –1 ) + ( d2 ⋅ z –2 ) + ( d3 ⋅ z –3 ) + ( d4 ⋅ z –4 )
The device provides the option for one of twelve low-pass filters. The filter is selected independently for each axis with the
LPF_X[3:0] and LPF_Y[3:0] bits in the DEVCFG_X and DEVCFG_Y registers. The filter selection options are listed in
Section 3.1.7.3, Table 11. Response parameters for the low-pass filter are specified in Section 2.4. Filter characteristics are illustrated in the figures on the following pages.
MMA65xx
26
Sensor
Freescale Semiconductor, Inc.
Table 27. Low Pass Filter Coefficients
LPF_X/
Description
Filter
LPF_Y
Filter
-3dB Frequency
Number Value
Order
(±5%)
(HEX)
8
0
9
1
10
2
13
5
11
3
12
4
0x08
0x00
0x09
0x01
0x0A
0x02
0x0D
0x05
0x0B
0x03
0x0C
0x04
50 Hz LPF
100 Hz LPF
150 Hz LPF
300 Hz LPF
200 Hz LPF
400 Hz LPF
200 Hz LPF
400 Hz LPF
400 Hz LPF
800 Hz LPF
500 Hz LPF
1000 Hz LPF
4
4
4
4
4
4
3
3
4
4
4
4
Sample
Time
(μs ±5%)
16
8
16
8
16
8
16
8
16
8
16
8
Group
Delay
Filter Coefficients
n0
2.08729034056887e-10
d0
1
n1
8.349134489240434e-10
d1
-3.976249694824219
n2
1.25237777794924e-09
d2
5.929003009577855
n3
8.349103355433541e-10
d3
-3.929255528257727
n4
2.087307211059861e-10
d4
0.9765022168437554
n0
1.639127731323242e-08
d0
1
n1
6.556510925292969e-08
d1
-3.928921222686768
Self Test
Step
Response
(ms)
14.00
26816/
fosc
7.00
n2
9.834768482194806e-08
d2
5.789028996785419
n3
6.556510372902331e-08
d3
-3.791257019240902
n4
1.639128257923422e-08
d4
0.9311495074496179
n0
5.124509334564209e-08
d0
1
n1
2.049803733825684e-07
d1
-3.905343055725098
6.00
9024/
fosc
3.00
n2
3.074705789151505e-07
d2
5.72004239520561
n3
2.049803958150164e-07
d3
-3.723967810019985
n4
5.124510693742625e-08
d4
0.9092692903507213
n0
2.720393240451813e-06
d0
1
n1
8.161179721355438e-06
d1
-2.931681632995605
5.00
6784/
fosc
2.50
n2
8.161180123840722e-06
d2
2.865296718275204
n3
2.720393634345496e-06
d3 -0.9335933215174919
n4
0
d4
0
n0
7.822513580322266e-07
d0
1
n1
3.129005432128906e-06
d1
-3.811614513397217
n2
4.693508163398543e-06
d2
5.450666051045118
n3
3.129005428784364e-06
d3
-3.465805771100349
n4
7.822513604678875e-07
d4
0.8267667478030489
n0
1.865386962890625e-06
d0
1
n1
7.4615478515625e-06
d1
-3.765105724334717
4.80
5632/
fosc
2.40
2.50
3392/
fosc
1.70
n2
1.119232176112846e-05
d2
5.319861050818872
n3
7.4615478515625e-06
d3
-3.34309015036024
n4
1.865386966264658e-06
d4
0.7883646729233078
3.20
2688/
fosc
1.60
Note: Low Pass Filter figures do not include g-cell frequency response.
MMA65xx
Sensor
Freescale Semiconductor, Inc.
27
Figure 15. Low-Pass Filter Characteristics: fC = 100 Hz, Poles = 4, tS = 8 μs
MMA65xx
28
Sensor
Freescale Semiconductor, Inc.
Figure 16. Low-Pass Filter Characteristics: fC = 300 Hz, Poles = 4, tS = 8 μs
MMA65xx
Sensor
Freescale Semiconductor, Inc.
29
Figure 17. Low-Pass Filter Characteristics: fC = 400 Hz, Poles = 4, tS = 8 μs
MMA65xx
30
Sensor
Freescale Semiconductor, Inc.
Figure 18. Low-Pass Filter Characteristics: fC = 400 Hz, Poles = 3, tS = 8 μs
MMA65xx
Sensor
Freescale Semiconductor, Inc.
31
Figure 19. Low-Pass Filter Characteristics: fC = 800 Hz, Poles = 4, tS = 8 μs
MMA65xx
32
Sensor
Freescale Semiconductor, Inc.
Figure 20. Low-Pass Filter Characteristics: fC = 1000 Hz, Poles = 4, tS = 8 μs
MMA65xx
Sensor
Freescale Semiconductor, Inc.
33
3.8.4
Offset Cancellation
The device provides the option to read offset cancelled acceleration data via the SPI by clearing the OC bit in the DEVCFG
register (reference Section 3.1.6.1) and in the SPI command (reference Section 4.1). A block diagram of the offset cancellation
is shown in Figure 21, and response parameters are specified in Section 2.4 and in Table 28.
Downsampled to 256μs
LPFOUT
T Registers updated every 1.049s
Accumulator
Shift
4096 samples
T1
T2
T3
T4
OFFTHRNEG
T5
T6
OFF_ERR
1.049s
OFF_ERR
OFFTHRPOS
Updated every 1.049s
1/8 LSB
Increment 1/4 LSB
6.291s Average
Offset Inc/Dec
Decrement 1/4 LSB
1/8 LSB
OFFCORRP
OFF_CORR_VALUE
OCOUT
OFFCORRN
Alignment
Correction
Figure 21. Offset Cancellation Block Diagram
In normal operation, the offset cancellation circuit computes a 24,576 sample running average of the acceleration data downsampled to 256 μs. The running average is compared against positive and negative thresholds to determine the offset correction
value that will be applied to the acceleration data.
During start up, three phases of moving average sizes are used to allow for faster convergence of misuse input signals. Reference Table 28 for offset cancellation timing information during startup and normal operation. The offset cancellation startup
phase can also be directly controlled during initialization (ENDINIT = ‘0’) using the OCPHASE[1:0] bits and the OFFCFG_EN bit
in the DEVCTL register, as described in Section 3.1.5.2 and Section 3.1.5.3.
Table 28. Offset Cancellation Timing Specifications
Phase
Start Time of
Phase
(from POR)
Typical
# of Samples in
Time in
Phase
Phase (ms)
Samples
Averaged
OFF_CORR_VALUE
Update Rate
(ms)
Averaging
Period
(ms)
Maximum
Slew Rate
(LSB/s)
Averaging Filter
-3dB Frequency
(Hz)
Start 1
tOP
524.288
2048
48
2.048
12.288
122.1
36.05
Start 2
tOP + 524.288
524.288
2048
384
16.38
98.304
15.26
4.506
Start 3
tOP + 1048.576
524.288
2048
3072
131.1
786.432
1.907
0.5632
Normal
tOP + 1572.864
—
—
24576
1049
6291.456
0.2384
0.07040
When the self test circuitry is active, the offset cancellation block and the offset monitor block are suspended, and the offset
correction value is constant. Once the self test circuitry is disabled, the offset cancellation block remains suspended for the time
tST_OMB to allow the acceleration output to return to it’s nominal offset.
3.8.5
Offset Monitor
The device provides the option for an offset monitor circuit. The offset monitor circuit is enabled when the OFMON bit in the
DEVCFG register is programmed to a logic ‘1’. The output of the offset cancellation circuit is compared against a high and low
threshold. If the offset correction value exceeds either the OFFTHRPOS, or OFFTHRNEG threshold, an Offset Over Range Error
condition is indicated.
The offset correction value update rate is listed in Table 28: “Maximum Slew Rate”. Because the offset monitor uses this value,
the offset monitor will also update at this rate. The time to indicate an Offset Over Range Error is dependent upon the input signal.
The offset monitor status remains suspended during self test, because the offset monitor is based on the offset cancellation
circuit, which is also suspended during self test. The offset monitor is disabled for 2.1 seconds following reset regardless of the
state of the OFMON bit.
MMA65xx
34
Sensor
Freescale Semiconductor, Inc.
3.8.6
Signal Compensation
The device includes internal OTP and signal processing to compensate for sensitivity error and offset error. This compensation
is necessary to achieve the specified parameters in Section 2.4.
3.8.7
Output Scaling
The 20 bit digital output from the DSP is clipped and scaled to a 12-bit data word which spans the acceleration range of the
device. Figure 22 shows the method used to establish the output acceleration data word from the DSP output.
Over Range
Signal
D19 D18 D17 D16 D15 D14 D13 D12 D11 D10 D9
12-Bit Data Word
D15 D14 D13 D12 D11 D10 D9
Noise
D8
D7
D6
D5
D4
D8
D7
D6
D5
D4
D3
D2
D1
D0
Using Rounding
Figure 22. 12-Bit Output Scaling Diagram
3.8.8
Data Interpolation
The device includes 2 to 1 data interpolation to minimize the system sample jitter. Each result produced by the digital signal
processing chain is delayed one half of a sample time, and the interpolated value of successive samples is provided between
sample times. This operation is illustrated below.
Sn-3
Sn-2
Sn-1
Sn
Internal Sample Rate
t
ts
ts
Sn-3
Sn – 3 + Sn – 2
------------------------------2
Sn-2
ts
Sn – 2 + Sn – 1
------------------------------2
Sn-1
Sn – 1 + Sn
----------------------2
Output Sample Rate
t
SPI acceleration request occurring in this window receives interpolated sample
SPI acceleration request occurring in this window receives true sample.
Figure 23. Data Interpolation Timing
MMA65xx
Sensor
Freescale Semiconductor, Inc.
35
The effect of this interpolation at the system level is a 50% reduction in sample jitter. Figure 24 shows the resulting output data
for an input signal.
80
75
Internally
Sampled Values
70
Counts
65
60
Fixed Latency:
tS / 2
Earliest Transmission
Point of Interpolated
Values
55
Earliest Transmission
Point of Internally
Sampled Values
50
45
Window of
Transmission for
Interpolated Values
(Maximum: tS / 2)
Window of
Transmission for
= Signal Jitter = Sampled Values
(Maximum: tS / 2)
40
0
5
10
15
Input Signal
Internally Sampled Signal
Interpolated Samples
20
25
30
35
40
Time
Figure 24. Data Interpolation Example
3.8.9
Acceleration Data Timing
The SPI uses a request/response protocol, where a SPI transfer is completed through a sequence of 2 phases. Reference
Section 4 for more details regarding the SPI protocol. The device latches the associated data for an acceleration request at the
rising edge of CS. The most recent sample available from the DSP (including interpolation) is latched, and transmitted during the
subsequent SPI transfer.
SCLK
CS
MOSI
Request X-Axis
Request Y-Axis
Request X-Axis
Request Y-Axis
X-Axis Response
Y-Axis Response
X-Axis Response
MISO
X-Axis Data Latched
X-Axis Arm Function updated
Y-Axis Data Latched
Y-Axis Arm Function updated if applicable
Figure 25. Acceleration Data Timing
MMA65xx
36
Sensor
Freescale Semiconductor, Inc.
3.8.10
ARMING FUNCTION
The device provides the option for an arming function with 3 modes of operation. The operation of the arming function is selected by the state of the A_CFG bits in the DEVCFG register.
Reference Section 4.5 for the operation of the Arming function with exception conditions. Error conditions do not impact prior
arming function responses. If an error occurs after an arming activation, the corresponding pulse stretch for the existing arming
condition will continue. However, new acceleration reads will not update the arming function regardless of the acceleration value.
3.8.10.1
Arming Function: Moving Average Mode
In moving average mode, the arming function runs a moving average on the offset cancelled output of each acceleration axis.
The number of samples used for the moving average (k) is programmable via the AWS_Xx[1:0] and ARM_Yx[1:0] bits in the
ARMCFGX and ARMCFGY registers. Reference Section 3.1.8 for register details.
ARM_MAn = (OCn + OCn-1 + ... + OCn+1-k)/k
Where n is the current sample.
The sample rate for each axis is determined by the SPI acceleration data sample rate. At the rising edge of CS for an acceleration data SPI request, the moving average for the associated axis is updated with a new sample. Reference Figure 28. The
SPI acceleration data sample rate must meet the minimum time between requests (tACC_REQ_x) specified in Section 2.6.
The moving average output is compared against positive and negative 8-bit thresholds that are individually programmed for
each axis via the ARMT_Xx and ARMT_Yx registers. Reference Section 3.1.10 for register details. If the moving average equals
or exceeds either threshold, an arming condition is indicated, the ARM_X or ARM_Y output is asserted for the associated axis,
and the pulse stretch counter is set as described in Section 3.8.10.4.
The ARM_X or ARM_Y output is de-asserted only when the pulse stretch counter expires. Figure 28 shows the arming output
operation for different SPI conditions.
ARMT_xP[7:0]
AWS_xP[1:0]
Positive
Moving Average
Offset Cancellation
Pulse Stretch
OffCanc_ARM_x[10:0]
AWS_xN[1:0]
Gating
I/O
ARM_x
Negative
Moving Average
ARMT_xN[7:0]
APS_x[1:0]
Figure 26. Arming Function Block Diagram - Moving Average Mode
The moving average window size must be set prior to setting the arming function to moving average mode, or prior to requesting acceleration data via the SPI. If the moving average window size is changed after enabling moving average mode, the arming
function must first be disabled by setting the A_CFG bits to “000”. Once the desired moving average window size is set, the moving average mode can be re-enabled.
MMA65xx
Sensor
Freescale Semiconductor, Inc.
37
3.8.10.2
Arming Function: Count Mode
In count mode, the arming function compares each offset cancelled sample against positive and negative thresholds that are
individually programmed for each axis via the ARMT_Xx and ARMT_Yx registers. Reference Section 3.1.10 for register details.
If the sample equals or exceeds either threshold, a sample counter is incremented. If the sample does not exceed either threshold, the sample counter is reset to zero.
The sample rate for each axis is determined by the SPI acceleration data sample rate. At the rising edge of CS for an acceleration data SPI request, a new sample for the associated axis is compared against the thresholds. Reference Figure 28. The
SPI acceleration data sample rate must meet the minimum time between requests (tACC_REQ_x) specified in Section 2.6.
A sample count limit is programmable via the AWS_Xx[1:0] and AWS_Yx[1:0] bits in the ARMCFGX and ARMCFGY registers.
If the sample count reaches the programmable sample count limit, an arming condition is indicated, the ARM_X or ARM_Y output
is asserted for the associated axis, and the pulse stretch counter is set as described in Section 3.8.10.4.
The ARM_X or ARM_Y output is de-asserted only when the pulse stretch counter expires. Figure 28 shows the arming output
operation for different SPI conditions.
AWS_xP[1:0]
ARMT_xP[7:0]
Offset Cancellation
1-4 Sample
Pulse Stretch
Counter
OffCanc_ARM_x[10:0]
Gating
I/O
ARM_x
ARMT_xN[7:0]
APS_x[1:0]
Figure 27. Arming Function Block Diagram - Count Mode
SCLK
CS
MOSI
Request X-Axis
Request Y-Axis
Request X-Axis
Request Y-Axis
Y-Axis Response
X-Axis Response
Y-Axis Response
X-Axis Response
Y-Axis Arm Condition
Not Present
X-Axis Arm Condition
Present
Y-Axis Arm Condition
Present
X-Axis Arm Condition
Not Present
MISO
ARM_X
ARM_Y
X-Axis Data
Latched for
Arm & SPI
Y-Axis Data
Latched for
Arm & SPI
X-Axis Data
Latched for
Arm & SPI
Y-Axis Pulse Stretch
tARM
X-Axis Pulse Stretch
Figure 28. X and Y Axis Arming Conditions, Moving Average and Count Mode
MMA65xx
38
Sensor
Freescale Semiconductor, Inc.
3.8.10.3
Arming Function: Unfiltered Mode
On the rising edge of CS for an acceleration request, the most recent available offset cancelled sample for the requested axis
is compared against positive and negative thresholds that are individually programmed for each axis via the ARMT_Xx and
ARMT_Yx registers. Reference Section 3.1.10 for register details. If the sample equals or exceeds either threshold, an arming
condition is indicated.
Once an arming condition is indicated for the X-Axis, the ARM_X output is asserted when CS is asserted and the MISO data
includes an acceleration response for that axis.
Once an arming condition is indicated for the Y-Axis, the ARM_Y output is asserted when CS is asserted and the MISO data
includes an acceleration response for that axis.
The pulse stretch function is not applied in Unfiltered mode.
Figure 29 contains a block diagram of the Arming Function operation in Unfiltered Mode. Figure 30 shows the Arming output
operation under the different SPI request conditions.
ACFG[2]
ACFG[1]
CS
I/O
AXIS Select
ARM_x
ARMING FUNCTION
Interpolated Sample Rate
Figure 29. Arming Function Block Diagram - Unfiltered Mode
SCLK
CS
MOSI
Request X-Axis
Request Y-Axis
Request X-Axis
Request Y-Axis
Y-Axis Response
X-Axis Response
Y-Axis Response
X-Axis Response
Y-Axis Arm Condition
Not Present
X-Axis Arm Condition
Present
Y-Axis Arm Condition
Present
X-Axis Arm Condition
Not Present
MISO
ARM_X
ARM_Y
Y-Axis Data
Latched for
Arm & SPI
X-Axis Data
Latched for
Arm & SPI
tARM_UF_DLY
tARM_UF_ASSERT
X-Axis Data
Latched for
Arm & SPI
tARM_UF_DLY
tARM_UF_ASSERT
Figure 30. X and Y Axis Arming Conditions, Unfiltered Mode
MMA65xx
Sensor
Freescale Semiconductor, Inc.
39
3.8.10.4
Arming Pulse Stretch Function
A pulse stretch function can be applied to the arming outputs in moving average mode, or count mode.
If the pulse stretch function is not used (APS_X[1:0] = ‘00’ or APS_Y[1:0] = ‘00’), the arming output is asserted if and only if
an arming condition exists for the associated axis after the most recent evaluated sample. The arming output is de-asserted if
and only if an arming condition does not exist for the associated axis after the most recent evaluated sample.
If the pulse stretch function is used, (APS_X[1:0] not equal ‘00’ or APS_Y[1:0] not equal ‘00’), the arming output is controlled
only by the value of the pulse stretch timer value. If the pulse stretch timer value is non-zero, the arming output is asserted. If the
pulse stretch timer is zero, the arming output is de-asserted. The pulse stretch counter continuously decrements until it reaches
zero. The pulse stretch counter is reset to the programmed pulse stretch value if and only if an arming condition exists for the
associated axis after the most recent evaluated sample. Reference Figure 28.
The desired pulse stretch time is individually programmable for each axis via the APS_X[1:0] and APS_Y[1:0] bits in the ARMCFG register.
Exception conditions listed in Section 4.5 do not impact prior arming function responses. If an exception occurs after an arming
activation, the corresponding pulse stretch for the existing arming condition will continue. However, new acceleration reads will
not reset the pulse stretch counter regardless of the acceleration value.
3.8.10.5
Arming Pin Output Structure
The arming output pin structure can be set to active high, or active low with the A_CFG bits in the DEVCFG register as described in Section 3.1.6.6. The active high and active low pin output structures are shown in Figure 31.
Open Drain, Active High
Open Drain, Active Low
VCC
Arm Function
Gating
VCC
ARM_x
ARM_x
Arm Function
Gating
Figure 31. Arming Function - Pin Output Structure
MMA65xx
40
Sensor
Freescale Semiconductor, Inc.
3.8.11
PCM Output Function
The device provides the option for a PCM output function. The PCM output is enabled by setting the A_CFG bits in the
DEVCFG register to the appropriate state as described in Section 3.1.6.6. Selecting the PCM output enables the following functions:
• The PCM_X and PCM_Y pins are programmed as a digital outputs. Reference Section 2.3 for the pin electrical
parameters.
• The acceleration value output from the offset cancellation block is saturated to 9-bits and converted to an unsigned value.
Note, the 9-bit unsigned acceleration value uses the full range of values (0 - 511).
• The 9-bit acceleration value is input into a summer clocked at 8MHz.
• The carry from the summer circuit is output to the PCM pin.
A block diagram of the PCM output is shown in Figure 32.
Exception conditions affect the PCM output as listed in Section 4.5.
Output Scaling
9
A
CARRY
ARM_x/PCM_x
OC_x[9:1]
9 Bit ADDER
9
Sample updated every 8μS
B
SUM
fCLK = 8 MHz
D
D
Q
Q
Q
D
Q
D
Q
FF
D
Q
FFD
Q
FFD
Q
FFD
Q
FF
CLK
Q FFFF
CLK
Q FF
CLK
Q FF
CLK
Q
CLK
Q
CLK
Q
CLK
Q
CLK
Q
CLK
Q
D
9
Figure 32. PCM Output Function Block Diagram
MMA65xx
Sensor
Freescale Semiconductor, Inc.
41
3.9
Serial Peripheral Interface
The device includes a Serial Peripheral Interface (SPI) to provide access to the configuration registers and digital data. Reference Section 4 for details regarding the SPI protocol and available commands.
To maximize independence between the X and Y channels, the device includes two interface blocks, one for each axis. The
X-axis interface block responds only to X-axis acceleration requests, or even addressed register commands. The Y-axis interface
block responds only to Y-axis acceleration requests, or odd addressed register commands. To the SPI master, the device operates as a single device. The internal independent blocks are transparent.
Each SPI block has an independent shift register. Once a message is received (rising edge of CS), the contents of the two
shift registers are compared. If the contents do not match, the Y-Axis SPI block will not respond, and the X-Axis SPI block will
respond with a SPI Error as shown in Table 30. If the contents match, each SPI block decodes the message, and the appropriate
block enables DO for a response during the next SPI message.
Figure 33 shows an internal diagram of the SPI.
Registers
X SPI
If Bit 13 == ‘1’
If Bit 13 = ‘0’
& Bit 14 == ‘0’
& A0 == ‘0’
SPI Master
Even Address Regs
X SPI Shift Register
X-Axis Raw Data
X-Axis OC Data
CS_M
SPI Mismatch Error (SPI Error)
CS
CS
SCLKM SCLK
SCLK
MOSIM
MOSI
MOSI
MISOM
MISO
MISO
I/O
Odd Address Regs
Y SPI Shift Register
Y-Axis Raw Data
Y-Axis OC Data
Y SPI
If Bit 13 == ‘1’
If Bit 13 = ‘0’
& Bit 14 == ‘1’
& A0 == ‘1’
Figure 33. SPI Diagram
MMA65xx
42
Sensor
Freescale Semiconductor, Inc.
3.10
Device Initialization
Following power-up, under-voltage reset, or a SPI reset command sequence, the device proceeds through an internal initialization process as shown below. Figure 34 also shows the device performance for an example external system level initialization
procedure.
Internal Initialization
OTP Copy to
Offset Cancellation
Offset Cancellation
Offset Cancellation
Offset Cancellation
Mirror Registers
Startup Phase 1
Startup Phase 2
Startup Phase 3
Normal Mode
tOC_PHASE1
tOC_PHASE2
tOC_PHASE3
External Initialization
Delay
Read DEVSTAT
Verify X-Axis
to clear flags
Self Test &
Verify X-Axis
Re-read DEVSTAT
ARM_X Asserted
to verify Status Dly
Dly
Offset
Verify Y-Axis
Initialize R/W
Offset & ARM_Y
Registers to
DeAsserted
Desired State
Dly
Re-Initialize
Verify X-Axis
Offset & ARM_X R/W Registers
Normal
DeAsserted
(if needed)
Dly
Mode
Verify Y-Axis
Verify Y-Axis
and
Self Test &
Offset & ARM_Y
Set ENDINIT
ARM_Y Asserted
DeAsserted
Verify X-Axis
Offset & ARM_X
DeAsserted
tSTRISE
tOP
X_ST
Assertion
Dependent on
Arming Mode
X_ARM
DeAssertion
Dependent on Pulse
Stretch and/or Arming Mode
tST_OMB
Y_ST
tSTFALL
Assertion
Dependent on
Arming Mode
Y_ARM
POR
Ready for SPI
Command
ENDINIT Clear
Internal
Offset Error
Corrected to ‘0’
Activate
X-Axis
Self Test
DeActivate
X-Axis
Self Test
Activate
Y-Axis
Self Test
DeAssertion
Dependent on Pulse
Stretch and/or Arming Mode
DeActivate
Y-Axis
Self Test
Notes:1) X-Axis and Y-Axis Self Test can be enabled and evaluated simultaneously to reduce test time.
For failure mode coverage of the arming pins and of potential common axis failures, Freescale recommends independent self test activation.
2) tSTRISE and tSTFALL are dependent on the selected LPF group delay.
Figure 34. Initialization Process
MMA65xx
Sensor
Freescale Semiconductor, Inc.
43
3.11
Overload Response
3.11.1
Overload Performance
The device is designed to operate within a specified range. Acceleration beyond that range (overload) impacts the output of
the sensor. Acceleration beyond the range of the device can generate a DC shift at the output of the device that is dependent
upon the overload frequency and amplitude. The g-cell is overdamped, providing the optimal design for overload performance.
However, the performance of the device during an overload condition is affected by many other parameters, including:
• g-cell damping
• Non-linearity
• Clipping limits
• Symmetry
Figure 35 shows the g-cell, ADC and output clipping of the device over frequency. The relevant parameters are specified in
Section 2.1, and Section 2.7.
g-cellRolloff
Acceleration (g)
Region Clipped
by Output
LPFRolloff
ion
Reg
b
ped
Clip
y g-
cell
Determined by g-cell
roll-off and ADC clipping
o
ue t
ADC
on d earity
i
t
y
r
b
o
t
in
ed
l Dis on-L
lipp
igna and N
nC
S
o
i
f
g
o
Re
etry
ion
Reg Asymm
gg-cell_Clip
gADC_Clip
Determined by g-cell
roll-off and full scale range
gRange_Norm
Region of Interest
fLPF
Region of No Signal Distortion Beyond
Specification
fg-Cell
5kHz
10kHz
Frequency (kHz)
Figure 35. Output Clipping Vs. Frequency
3.11.2
Sigma Delta Over Range Response
Over range conditions exist when the signal level is beyond the full-scale range of the device but within the computational limits
of the DSP. The ΣΔ converter can saturate at levels above those specified in Section 2.1 (GADC_CLIP). The DSP operates predictably under all cases of over range, although the signal may include residual high frequency components for some time after
returning to the normal range of operation due to non-linear effects of the sensor.
MMA65xx
44
Sensor
Freescale Semiconductor, Inc.
4
SPI Communications
Communication with the device is completed through synchronous serial transfers via SPI. The device is a slave device configured for CPOL = 0, CPHA = 0, MSB first. SPI transfers are completed through a sequence of two phases. During the first
phase, the type of transfer and associated control information is transmitted from the SPI master to the device. Data from the
device is transmitted during the second phase. Any activity on MOSI or SCLK is ignored when CS is negated. Consequently,
intermediate transfers involving other SPI devices may occur between phase one and phase two. Reference Figure 36.
SCLK
CS
MOSI
Phase One: Command
Phase Two: Response
Phase One: Response -Previous Command
MISO
SCLK
CS
MOSI
T1P1
T2P1
T3P1
T1P2
T2P2
T3P2
MISO
Figure 36. SPI Transfer Detail
MMA65xx
Sensor
Freescale Semiconductor, Inc.
45
4.1
SPI Command Format
Commands are transferred from the SPI master to the device. Valid commands fall into two categories: register operations,
and acceleration data requests.
Table 29. SPI Command Message Summary
MSB
LSB
15
14
0
AX
13
12
11
10
9
8
7
6
5
4
3
2
1
0
A
OC
0
0
0
0
0
0
0
0
1
SD
ARM
P
Command Type
Reference
AX= Axis Selection
0
X-Axis Acceleration Data
1
Y-Axis Acceleration Data
A = Acceleration Data Request
0
1
Register Operation
Acceleration Data Request
OC = Offset Cancelled Data Confirmation
0
Offset Cancelled Data Enabled
1
Raw Acceleration Data Enabled
SD = Signed Data Confirmation
Signed Data Enabled
0
Unsigned Data Enabled
1
ARM = ARM Function Status Confirmation
Disabled / PCM Output Enabled
0
Arming Function Enabled
1
P = Odd Parity
0
AX
A
OC
0
0
0
0
0
0
0
0
0
SD
ARM
P
Accel Data
0
0
1
0
0
0
0
0
0
0
0
0
1
0
0
1
X-Axis OC, Signed, Disabled/PCM
0
0
1
0
0
0
0
0
0
0
0
0
1
0
1
0
X-Axis OC, Signed, ARM Enabled
0
0
1
0
0
0
0
0
0
0
0
0
1
1
0
0
X-Axis OC, Unsigned, Disabled/PCM
0
0
1
0
0
0
0
0
0
0
0
0
1
1
1
1
X-Axis OC, Unsigned, ARM Enabled
0
0
1
1
0
0
0
0
0
0
0
0
1
0
0
0
X-Axis Raw, Signed, Disabled/PCM
0
0
1
1
0
0
0
0
0
0
0
0
1
0
1
1
X-Axis Raw, Signed, ARM Enabled
0
0
1
1
0
0
0
0
0
0
0
0
1
1
0
1
X-Axis Raw, Unsigned, Disabled/PCM
0
0
1
1
0
0
0
0
0
0
0
0
1
1
1
0
X-Axis Raw, Unsigned, ARM Enabled
0
1
1
0
0
0
0
0
0
0
0
0
1
0
0
0
Y-Axis OC, Signed, Disabled/PCM
0
1
1
0
0
0
0
0
0
0
0
0
1
0
1
1
Y-Axis OC, Signed, ARM Enabled
0
1
1
0
0
0
0
0
0
0
0
0
1
1
0
1
Y-Axis OC, Unsigned, Disabled/PCM
0
1
1
0
0
0
0
0
0
0
0
0
1
1
1
0
Y-Axis OC, Unsigned, ARM Enabled
0
1
1
1
0
0
0
0
0
0
0
0
1
0
0
1
Y-Axis Raw, Signed, Disabled/PCM
0
1
1
1
0
0
0
0
0
0
0
0
1
0
1
0
Y-Axis Raw, Signed, ARM Enabled
0
1
1
1
0
0
0
0
0
0
0
0
1
1
0
0
Y-Axis Raw, Unsigned, Disabled/PCM
0
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
Y-Axis Raw, Unsigned, ARM Enabled
P
AX
A
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
Command Type
Reference
A3
A2
A1
A0
P
0
0
0
0
0
0
0
0
0
0
Register Read
Section 4.4
D7
D6
D5
D4
D3
D2
D1
D0
Register Write
Section 4.4
A4
Register Address
A4
P
1
A3
A2
A1
A0
0
Register Address
Data to be Written to Register
P = Odd Parity
MMA65xx
46
Sensor
Freescale Semiconductor, Inc.
4.2
SPI Response Format
Table 30. SPI Response Message Summary
MSB
LSB
15
14
13
12
11
D15
D14
AX
P
D11
D1
D0
10
9
8
7
6
5
4
3
2
1
0
Response to Valid Acceleration Request
CMD
A
AX
Reference
D10
Acceleration
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D5
D4
D3
D2
AX = Axis Requested
0
X-Axis Acceleration Response
1
Y-Axis Acceleration Response
P = Odd Parity
S[1:0] = Device Status
CMD
Valid Accel Request
D1
D0
0
0
In Initialization (ENDINIT = ‘0’)
0
1
Normal Request
1
0
ST Active
1
1
Internal Error Present / SPI Error
A
AX
AX
P
S1
S0
1
0
Accel Data
0
P
0
1
D11
D10
D9
X- Axis Acceleration Data
D8
D7
D6
1
0
Accel Data
0
P
1
0
X- Axis Self Test Active Acceleration Data
1
0
Accel Data
0
P
0
0
X- Axis Acceleration Data, Initialization in Process (ENDINIT=’0’)
1
1
Accel Data
1
P
0
1
Y-Axis Acceleration Data
1
1
Accel Data
1
P
1
0
Y-Axis Self Test Active Acceleration Data
1
1
Accel Data
1
P
0
0
Y- Axis Acceleration Data, Initialization in Process (ENDINIT=’0’)
Reference
Section 4.3
MSB
15
LSB
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Response to Valid Register Access
CMD
Register Write
A
0
AX
1
Reference
D15
D14
AX
P
D11
D10
D9
D8
0
0
1
P
1
1
1
0
D7
D6
D5
D4
D3
D2
D1
D0
D7
D6
D5
D4
D3
D2
D1
D0
Section 4.4.1
New Contents of Register
D7
Register Read
0
0
0
1
0
P
1
1
1
D6
D5
D4
D3
D2
D1
D0
0
Section 4.4.2
Contents of Register
MSB
15
LSB
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Error Responses
CMD
Invalid Accel
Request
A
x
AX
Reference
D15
D14
AX
P
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
0
0
AX
P
1
1
0
0
0
0
0
0
0
0
0
0
x
Internal
Error Present
x
x
MISO Error
x
x
Section 4.3
Section 4.5.5
Section 4.5.2
0
0
0
P
1
1
0
0
0
0
0
0
0
0
0
0
SPI Error
x
x
Invalid Register
Request
Section 4.5.1
0
x
0
0
0
0
1
1
1
0
0
0
0
0
0
0
0
0
Section 4.4
Self Test Error
0
x
0
0
AX
P
1
1
0
0
0
0
0
0
0
0
0
0
Section 4.5.5
MMA65xx
Sensor
Freescale Semiconductor, Inc.
47
4.3
Acceleration Data Transfers
Twelve bit Acceleration data requests are initiated when the Acceleration bit of the SPI command message (A) is set to a logic
‘1’, and bit D[3] of the SPI command message is set to a logic ‘1’. The Axis Selection bit (AX) selects the type of acceleration data
requested, as shown in Table 31.
Table 31. Acceleration Data Request
Axis Selection Bit (AX)
Data Type
0
X-Axis Acceleration Data
1
Y-Axis Acceleration Data
To verify that the device is configured as expected, each acceleration data request includes the configuration information which
impacts the output data. The requested configuration is compared against the data programmed in the writable register block.
Details are shown in Table 32.
Table 32. Acceleration Data Request Configuration Information
Programmable Option
Command Message Bit
Writable Register Information
Raw or Offset Cancelled Data
OC
DEVCFG[7] (OC)
Signed or Unsigned Data
SD
DEVCFG[4] (SD)
Arming Function or PCM Output
ARM
DEVCFG[2] || DEVCFG[1] (A_CFG[2] || A_CFG[1])
If the data listed in Table 32 does not does not match, an Acceleration Data Request Mismatch failure is detected and no acceleration data is transmitted. Reference Section 4.5.3.1.
Acceleration data request commands include a parity bit (P). Odd parity is employed. The number of logic ‘1’ bits in the acceleration data request command must be an odd number.
Acceleration data is transmitted on the next SPI message if and only if all of the following conditions are met:
• The DEVINIT bit in the DEVSTAT register is not set
• The DEVRES bit in the DEVSTAT register is not set
• The IDE bit in the DEVSTAT register is not set (Reference Section 4.5.5)
• No SPI Error is detected (Reference Section 4.5.1)
• No MISO Error is detected (Reference Section 4.5.2)
• No Acceleration Data Request Mismatch failure is detected (Reference Section 4.5.3.1)
• No Self Test Error is present (reference Section 4.5.5.2)
• No Offset Monitor Error is present for the requested channel (reference Section 4.5.6)
If the above conditions are met, the device responds with a “valid acceleration data request” response as shown in Table 30.
Otherwise, the device responds as specified in Section 4.5.
MMA65xx
48
Sensor
Freescale Semiconductor, Inc.
4.4
Register Access Operations
Two types of register access operations are supported; register write, and register read. Register access operations are initiated when the acceleration bit (A) of the command message is set to a logic ‘0’. The operation to be performed is indicated by
the Access Selection bit (AX) of the command message.
Access Selection Bit (AX)
Operation
0
Register Read
1
Register Write
Register Access operations include a parity bit (P). Odd parity is employed. The number of logic ‘1’ bits in the Register Access
operation must be an odd number.
4.4.1
Register Write Request
During a register write request, bits 12 through 8 contain a five-bit address, and bits 7 through 0 contain the data value to be
written. Writable registers are defined in Table 3.
The response to a register write operation is shown in Table 30. The response is transmitted on the next SPI message if and
only if all of the following conditions are met:
• No SPI Error is detected (Reference Section 4.5.1)
• No MISO Error is detected (Reference Section 4.5.2)
• The ENDINIT bit is cleared (Reference Section 3.1.6.3)
– This applies to all registers with the exception of the DEVCTL register (Only Bits 6 and 7 can be modified)
• No Invalid Register Request is detected (Reference Section 4.5.3.2)
If the above conditions are met, the device responds to the register write request as shown in Table 30. Otherwise, the device
Responds as specified in Section 4.5.
Register write operations do not occur internally until the transfer during which they are requested has been completed. In the
event that a SPI Error is detected during a register write transfer, the write operation is not completed.
4.4.2
Register Read Request
During a register read request, bits 12 through 8 contain the five-bit address for the register to be read. Bits 7 through 0 must
be logic ‘0’. Readable registers are defined in Table 3.
The response to a register read operation is shown in Table 30. The response is transmitted on the next SPI message if and
only if all of the following conditions are met:
• No SPI Error is detected (Reference Section 4.5.1)
• No MISO Error is detected (Reference Section 4.5.2)
• No Invalid Register Request is detected (Reference Section 4.5.3.2)
If the above conditions are met, the device responds to the register read request as shown in Table 30. Otherwise, the device
responds as specified in Section 4.5.
MMA65xx
Sensor
Freescale Semiconductor, Inc.
49
4.5
Exception Handling
The following sections describe the conditions and the device response for each detectable exception. In the event that multiple exceptions exist, the exception response is determined by the priority listed in Table 33.
Table 33. SPI Error Response Priority
Effect on Data
Error Priority
Exception
SPI Data
Arming Output
PCM Output
1
SPI Error
Error Response
No Update
No Effect
2
SPI MISO Error
Error Response
No Update
No Effect
3
Invalid Request
Error Response
No Update
No Effect
4
DEVINIT Bit Set
Error Response
No Update
Disabled
5
DEVRES Error
Error Response
No Update
Disabled
6
CRC Error
Error Response
No Update
No Effect
7
Self Test Error
Error Response
No Update
No Effect
8
Offset Monitor Error
Error Response
No Update
No Effect
4.5.1
SPI Error
The following SPI conditions result in a SPI error:
• SCLK is high when CS is asserted
• The number of SCLK rising edges detected while CS is asserted is not equal to 16
• SCLK is high when CS is negated
• Command message parity error (MOSI)
• Bit 15 of Acceleration Data Request is not equal to ‘0’
• Bits 4 through 11 of an Acceleration Request are not equal to ‘0’
• Bits 3 of an Acceleration Request is not equal to ‘1’
• Bits 0 through 7 of a Register Read Request are not equal to ‘0’
The device responds to a SPI error with a “SPI Error” response as shown in Table 30. This applies to both acceleration data
request SPI errors, and Register Access SPI errors.
The arming function will not be updated if a SPI Error is detected. The PCM output is not affected by a SPI Error.
MMA65xx
50
Sensor
Freescale Semiconductor, Inc.
4.5.2
SPI Data Output Verification Error
The device includes a function to verify the integrity of the data output to the MISO pin. The function reads the data transmitted
on the MISO pin and compares it against the data intended to be transmitted. If any one bit doesn’t match, a SPI MISO Mismatch
Fault is detected and the MISOERR flag in the DEVSTAT register is set.
If a valid SPI acceleration request message is received during the SPI transfer with the MISO mismatch failure, the SPI acceleration request message is ignored and the device responds with a “MISO Error” response during the subsequent SPI message
(reference Table 30). The Arming function is not updated if a MISO mismatch failure occurs. The PCM function is not affected by
the MISO mismatch failure.
If a valid SPI register write request message is received during the SPI transfer with the MISO mismatch failure, the register
write is completed as requested, but the device responds with a “MISO Error” response as shown in Table 30, during the subsequent SPI message.
If a valid SPI register read request message is received during the SPI transfer with the MISO mismatch failure, the register
read is ignored and the device responds with a “MISO Error” response as shown in Table 30, during the subsequent SPI message. If the register read request is for the DEVSTAT register, the DEVSTAT register will not be cleared.
In all cases, the MISOERR flag in the DEVSTAT register will remain set until a successful SPI Register Read Request of the
DEVSTAT register is completed.
SPI DATA OUT SHIFT REGISTER
D
DATA OUT BUFFER
Q
D
Q
MISO
R
D
Q
MISO ERR
SCLK
R
Figure 37. SPI Data Output Verification
4.5.3
Invalid Requests
4.5.3.1
Acceleration Data Request Mismatch Failure
The device detects an “Acceleration Data Request Mismatch” error if the SPI “Acceleration Data Request” Command data
listed in Table 32 does not match the internal register settings. The device responds to an “Acceleration Data Request Mismatch”
error with an “Invalid Accel Request” response as specified in Table 30 on the subsequent SPI message only. No internal fault is
recorded. The arming function will not be updated if an “Acceleration Data Request Mismatch” Error is detected. The PCM output
is not affected by the “Acceleration Data Request Mismatch” error.
Register operations will be executed as specified in Section 4.4.
4.5.3.2
Invalid Register Request
The following conditions result in an “Invalid Register Request” error:
• An attempt is made to write to an un-writable register (Writable registers are defined in Section 3.1, Table 3). Attempts to
write to registers $09, $18, $19, $1A and $1B will result in an error.
• An attempt is made to write to a register while the ENDINIT bit in the DEVCFG register is set
– This applies to all registers with the exception of the DEVCTL register (Only Bits 6 and 7 can be modified)
An attempt is made to read an un-readable register (Readable registers are defined in Section 3.1, Table 3). Attempts to
read registers $09, $18, $19, $1A and $1B will result in an error.
The device responds to an Invalid Register Request” error with an “Invalid Register Request” response as shown in Table 30.
•
4.5.4
Device Reset Indications
If the DEVINIT, or DEVRES bit is set in the DEVSTAT register as described in Section 3.1.11, the device will respond to acceleration data requests with an “Internal Error Present” response until the bits are cleared in the DEVSTAT register. The DEVINIT
bit is cleared automatically when device initialization is complete (Reference tOP in Section 2.7). The DEVRES bit is cleared on
a read of the DEVSTAT register. The arming function will not be updated on Acceleration Data Request commands if the DEVINIT
or DEVRES bit is set in the DEVSTAT register. The PCM output is disabled if the DEVINIT or DEVRES bit is set.
MMA65xx
Sensor
Freescale Semiconductor, Inc.
51
4.5.5
Internal Error
The following errors will result in an internal error, and set the IDE bit in the DEVSTAT register:
• OTP CRC Failure
• Writable Register CRC Failure
• Self Test Error
• Invalid internal logic states
4.5.5.1
CRC Error
If the IDE bit is set in the DEVSTAT register due to one or more of the following errors, the device will respond to acceleration
data requests with an “Internal Error Present” response until the IDE bit is cleared in the DEVSTAT register.
• An OTP Shadow Register CRC failure as described in Section 3.2
• A Writable Register CRC failure as described in Section 3.2
• A clock monitor CRC failure as described in Section 3.4.2
The arming function will not be updated on Acceleration Data Request commands if a CRC Error is detected. The PCM output
is not affected by the CRC error.
If the CRC error is in the writable register array, and the ENDINIT bit in the DEVCFG register has been set, the error can only
be cleared by a device reset. The IDE bit will not be cleared on a read of the DEVSTAT register.
If the CRC error is in the OTP shadow register array, the error cannot be cleared.
Register operations will be executed as specified in Section 4.4.
4.5.5.2
Self Test Error
If the IDE bit is set in the DEVSTAT register due to a Self Test activation failure, the device will respond to acceleration data
requests with a “Self Test Error” response until the IDE bit is cleared in the DEVSTAT register. The arming function will not be
updated on Acceleration Data Request commands if a Self Test Error is detected. The PCM output is not affected by the Self Test
Error. The IDE bit in the DEVSTAT register will remain set until a read of the DEVSTAT register occurs, even if the internal failure
is removed. If the internal error is still present when the DEVSTAT register is read, the IDE bit will remain set.
Register operations will be executed as specified in Section 4.4.
4.5.6
Offset Monitor Error
If an offset monitor error is present as described in Section 3.8.5, the OFFSET_X or OFFSET_Y bit in the DEVSTAT register
will be set. The device will respond to an acceleration request for the corresponding axis with an “Internal Error Present” response
until the OFFSET_X or OFFSET_Y bit is cleared in the DEVSTAT register. The arming function will not be updated. Once the
error condition is removed, the OFFSET_X or OFFSET_Y bit in the DEVSTAT register will remain set until a read of the DEVSTAT
register occurs.
The PCM output is not affected by the offset monitor over range condition.
Register operations will be executed as specified in Section 4.4.
4.6
Initialization SPI Response
The first data transmitted by the device following reset is the SPI Error response shown in Table 30. This ensures that an unexpected reset will always be detectable. The device will respond to all acceleration data requests with the “Invalid Acceleration
Data Request” response until the DEVRES bit in the DEVSTAT register is cleared via a read of the DEVSTAT register. The arming
function will not be updated on Acceleration Data Request commands until the DEVRES bit in the DEVSTAT register is cleared.
MMA65xx
52
Sensor
Freescale Semiconductor, Inc.
4.7
Acceleration Data Representation
Acceleration values are determined from the 12-bit digital output (DV) using the following equations:
= Sensitivity LSB × DV
Acceleration = Sensitivity LSB × ( DV – 2048 )
Acceleration
For Signed Data
For Unsigned Data
The linear range of digital values for signed data is -1920 to +1920, and for unsigned data is 128 to 3968. Resulting ranges
and some nominal acceleration values are shown in the following table.
Table 34. Nominal Acceleration Data Values
Nominal Acceleration
Unsigned Digital Value
Signed Digital Value
105g
105g
120g
Unused
Unused
Unused
3969 - 4095
1921 - 2047
3968
1920
80.000
g
105.49
g
120.00
g
3967
1919
79.958
g
105.44
g
119.94
g
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2050
2
0.083333
g
0.1099
g
0.1250
g
2049
1
0.041667
g
0.0545
g
0.0625
g
2048
0
0
g
0
g
0
g
2047
-1
-0.041667
g
-0.0545
g
-0.0625
g
2046
-2
-0.083333
g
-0.1099
g
-0.1250
g
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
129
-1919
-79.958
g
-105.44
g
-119.94
g
128
-1920
-80.000
g
-105.49
g
-120.00
g
1 - 127
-1921 - 2048
Unused
Unused
Unused
0
0
Fault
Fault
Fault
MMA65xx
Sensor
Freescale Semiconductor, Inc.
53
Figure 38 shows the how the possible output data codes are determined from the input data and the error sources. The relevant parameters are specified in Section 2.4.
Figure 38. Acceleration Data Output Vs. Acceleration Input
MMA65xx
54
Sensor
Freescale Semiconductor, Inc.
5
Package
5.1
Case Outline Drawing
Reference Freescale Case Outline Drawing # 98ASA00090D
http://www.freescale.com/files/shared/doc/package_info/98ASA00090D.pdf
5.2
Recommended Footprint
Reference Freescale Application Note AN3111, latest revision:
http://www.freescale.com/files/sensors/doc/app_note/AN3111.pdf
Table 1. Revision History
Revision
number
Revision
date
3
03/2012
Description of changes
• Added SafeAssure logo, changed first paragraph and disclaimer to include trademark
information.
• Added devices to ordering table: MMA6519KW, MMA6525KW and MMA6527KW
MMA65xx
Sensor
Freescale Semiconductor, Inc.
55
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MMA65XX
Rev. 3
03/2012
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