Autonomous 8-Angle Tip-Over Sensor
with High Vibration Immunity
MXD6240/6241AU
FEATURES
8 Pin-programmable angle thresholds
Single-wire digital output
Fully autonomous- no uC required
Built-in self-test functionality
Small, 6-pin 3 x 3mm LCC package
Operates from 2.7V to 5.5V Supply
No sensor resonance
Vibration filter: tolerates 20 g p-p @ 50Hz
vibration with < 1º incremental angle error
High reliability automotive process
RoHS compliant
Operates from -40 C to +125 C
APPLICATIONS :
Motorcycle Fall-Down Detection
Off-Road Vehicles
Jetski, watercraft
Other Tip-Over Detection (Space heaters, Irons, etc)
VDD
P2 P1 P0
2-Axis
Sensor
Signal
Cond’g
&A/D
DSP &
Hyst.
Delay
3-state
Output
Driver
OUT
Trim &
Cal
Circuits
Ref &
Bias
Gen
Clock &
Timing
Gen
GND
Figure 1. FUNCTIONAL BLOCK DIAGRAM
DESCRIPTION:
The MXD6240/6241AU is an inclination sensor with 8
built-in, pin-programmable angle thresholds. If the
device orientation with respect to vertical exceeds the
programmed threshold angle, the digital output
changes state to alert the system to a tip-over or fall-
down event. An internal anti-vibration filter
provides >45dB attenuation above 25Hz, and >60dB
attenuation above 50Hz.
The MXD6240/6241AU is designed to run
autonomously, making it ideal for systems where there
is no uC available. One of eight threshold angles (40,
42.5, 45, 50, 55, 60, 65, and 70 degrees) is selected
by connecting each of three programming pins to Vdd
or Gnd. The threshold accuracy is guaranteed to meet
+/-5 degrees (max) over a temperature range of -20C
to +80C (Operation is guaranteed over -40C to
+125C).
A built-in self-test function can detect a fault in the
internal sensor, and if triggered will cause the output
to go to a high impedance state.
Information furnished by MEMSIC is believed to be accurate and reliable.
However, no responsibility is assumed by MEMSIC for its use, or for any
infringements of patents or other rights of third parties which may result from
its use. No license is granted by implication or otherwise under any patent or
patent rights of MEMSIC.
The MXD6240/6241AU uses MEMSIC’s proprietary
thermal accelerometer technology. Because the
sensing element uses heated gas molecules instead
of a mechanical beam structure, the device is
extremely robust and reliable, with 50,000g shock
tolerance, no possibility of “stiction”, virtually no
mechanical resonance, and extremely high accuracy
over temperature. This makes the device extremely
well suited to harsh or high vibration environments,
where other sensors can exhibit false readings due to
resonance or other errors.
The MXD6240AU output is a logic low under normal
operation, and logic high during tip-over; the
MXD6241AU uses the opposite output polarity
(normally high, low during tip-over). A high-Z output
state signifies an internal self-test failure.
Both devices operate from a single 2.7V to 5.5V
supply, and are packaged in a small 6-pin, 3x3x1 mm
LCC package.
MEMSIC,
Inc.
One Technology Drive, Suite 325, Andover, MA 01810, USA
Tel: +1 978 738 0900
Fax: +1 978 738 0196
www.memsic.com
MEMSIC MXC6240/41AU Rev.A (6/27/2016)
Page 1 of 6
Formal release date: 8/18/2016
SENSOR CHARACTERISTICS:
(TA=25C, V
DD
= 5V, unless otherwise specified. Typical values are specified at 25C)
Parameter
Threshold Angles
Threshold Accuracy (Note 1)
Threshold Error due to Vibration
(Note 2)
Sensor Bandwidth
Resonance
Shock Tolerance
Off-Axis Tilt Range
LOW-G Lockout Threshold
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Conditions
Pin-Programmable via P2, P1, P0
TA = -20C to +80C
20g p-p @ f
≥
25Hz
20g p-p @ f
≥
50Hz
(Note 3)
(Note 4)
(For rated accuracy)
(Note 5)
Min
Typ
40, 42.5,
45, 50,
55, 60,
65, 70
±2
±3
±0.5
11
Undetectable
50,000
±15
0.375
Max
Units
Deg
±5
Deg
Deg
Hz
Hz
g
Deg
g
Guaranteed by design and characterization, using ±4σ limits.
This is the incremental threshold error due to the vibration signal, applied parallel to the y axis
The sensor has an inherent low pass filter characteristic, which is very effective in attenuating out of band vibration.
The thermal accelerometer sensors use heated gas molecules, and have no measurable resonance
The LOW-G Lockout feature disables tip-over detection if the magnitude of both X and Y acceleration vectors fall below 0.375g (as in
the case of a free-fall or large off-axis tilt condition). See also “Fault Detection”.
ELECTRICAL SPECIFICATIONS:
(TA=25C, V
DD
= 5V, unless otherwise specified. Typical values are specified at 25C)
Parameter
Supply Voltage
Supply Current
Operating Temperature
Output Update Rate (ODR)
Power On Time
Power On Reset Threshold
VDD Rise Time
Note 6:
Note 7:
Conditions
Min
2.7
Typ
0.8
Max
5.5
3
125
3.3
500
1.6
8
Units
V
mA
C
Hz
ms
V
ms
-40
(Note 6)
VDD rising edge to angle detection active
0.8
(Note 7)
2.7
3
300
1.2
This is the rate at which the logic state of the OUTPUT pin is updated. The output will typically change state within 1 – 2 ODR cycles of
a change in tip-over orientation. The above applies for Vdd = 5V. At Vdd = 2.7V, the ODR slows by ~15%.
Maximum allowable power supply rise time from 0.25V to 2.7V (minimum). Slower VDD rise time may cause erroneous data retrieval
from OTP memory at power-up.
DIGITAL PARAMETERS
(TA=25C, V
DD
= 5V, unless otherwise specified. Typical values are specified at 25C)
Parameter
Logic Input Low
Logic Input High
Logic Output Low
Logic Output High
Logic Output High-Z
Note 8:
Conditions
P2, P1, P0 Inputs
P2, P1, P0 Inputs
Sinking 0.5mA (Note 8)
Sourcing 0.5mA (Note 8)
After sensor fault is detected
Min
0.7*Vdd
0.9*Vdd
Typ
0
Vdd
Max
0.3*Vdd
0.1*Vdd
Units
V
V
V
Mohm
1
The output driver is capable of sourcing and sinking much higher currents, but it is recommended to keep the load current below 0.5mA
to avoid thermal gradients which may affect the angle threshold accuracy.
MEMSIC MXC6240/41AU Rev.A (6/27/2016)
Page 2 of 6
Formal release date: 8/18/2016
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (V
DD
) ………………………..-0.5 to +7V
Storage Temperature
….……………-40C to
+150C
*Stresses above those listed under Absolute Maximum Ratings may cause
permanent damage to the device. This is a stress rating only; the functional
operation of the device at these or any other conditions above those indicated
in the operational sections of this specification is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect the
device’s reliability.
THRESHOLD PROGRAMMING GUIDE
P2
0
0
0
0
1
1
1
1
P1
0
0
1
1
0
0
1
1
P0
0
1
0
1
0
1
0
1
Threshold Angle
ϴ
40 degrees
45 degrees
50 degrees
55 degrees
60 degrees
65 degrees
70 degrees
42.5 degrees
PIN DESCRIPTION: LCC-6 Package
Pin
1
Name
OUT
Description
Digital Output. This pin will be
low under normal operation,
and will transition to high to
alert to a tip-over event
(MXD6240). The MXD6241
uses the opposite convention
(high under normal operation,
low to signify tip-over). A high
impedance state reflects a
fault condition in the sensor.
Programming pin. Sets the
threshold angle (see table).
Positive power supply.
Connect to 2.7V to 5.5V.
Bypass this to ground using a
tbd capacitor.
Programming pin. Sets the
threshold angle (see table).
Programming pin, sets the
threshold angle (see table).
Connect to power supply
ground.
I/O
O
MOUNTING ORIENTATION
(Threshold Angle =
ϴ
below)
(Off-Axis Tilt =
Ф
below)
2
3
P2
VDD
I
P
4
5
6
P1
P0
GND
I
I
P
Note the package must be oriented vertically as
shown in the figure above, so that when the detection
angle is zero, the edge of the package with pins 1 and
6 is on the bottom edge and parallel to the earth.
Off-axis tilt is the angle of the x-y plane of the device
from vertical (See figure above). As off-axis tilt
increases from 0 to 90 degrees, the magnitude of the
acceleration vector in the x-y plane decreases. If the
acceleration signal is too small, an accurate
determination of orientation cannot be made. For
orientation measurements to be valid, the off-axis tilt
must be less than the off-axis tilt threshold. Angle
accuracy is degraded when off-axis tilt angle exceeds
15 degrees. If the off axis tilt exceeds 60 degrees, the
angle detection function is disabled.
MEMSIC MXC6240/41AU Rev.A (6/27/2016)
Page 3 of 6
Formal release date: 8/18/2016
INTERNAL FAULT DETECTION
The MXD6240/6241 has a variety of internal fault
detection circuit features.
On power up, the internal circuitry checks for the
following condition:
(a)
Valid non-volatile memory contents. Within
10ms of VDD rising edge, a CRC algorithm
checks if any of the bits have changed from
their factory programmed values. On power
up, the OUT pin is high-Z. A transition to a
valid logic state signifies the successful
completion of the CRC self-check. If this test
fails, the output will remain in a high
impedance state until the power supply is
removed and re-applied, at which time the
self-test is repeated.
In addition to the above test done at power up, the
following monitoring is performed on a continuous
basis:
(b)
If at any time either the X or Y output exceeds
2g continuously for more than approximately 4
seconds (see Note 9), the output is set to a
high impedance state, and remains there for
as long as the condition persists
(c)
If at any time both the X and the Y outputs fall
below 0.375g (which is an indication of either
a free fall event, excessive off-axis tilt, or a
leak in the gas cavity), the angle-detection
function is disabled immediately, to prevent
false triggering of the angle comparator. If this
condition persists for more than approximately
4 seconds (See Note 9), the output will go to a
high impedance state for as long as the
condition persists.
In each of the above cases (b) and (c), the fault
detection circuitry takes precedence over the tip-over
detection circuitry (the output will remain in the high
impedance state regardless of the angle detected, for
as long as the fault condition persists).
RESPONSE TO VIBRATION
The MXD6240/6241 is unique in its vibration
characteristics, due both to its sensor structure, and
its signal processing features.
The MXD6241/6241 uses MEMSIC’s proprietary
thermal MEMS acceleration sensor, which uses
heated gas molecules in a sealed cavity. This
technology offers two distinct benefits: (a) The sensor
has no detectable resonance, and (b) The sensor has
an inherent low-pass frequency response, which
provides very effective filtering of unwanted vibration
signals prior to the electronic signal path. Additional
filtering is provided in the signal processing circuitry,
which enables the device to tolerate very high levels
of out-of-band vibration with negligible effect on angle
detection accuracy.
Figure A is a plot showing the worst case threshold
error caused by a 20g p-p vibration signal, swept from
10 Hz to 1 kHz. The angle error will scale linearly with
the vibration amplitude at any given frequency.
Figure A: Threshold Angle Error vs. Vibration
Frequency (simulated), 20g p-p Vibration Swept from
10Hz to 1kHz
1.E+01
Threshold Angle Error,
degrees
10
100
1000
1.E‐02
1.E‐05
Threshold…
1.E‐08
MEMSIC has some flexibility in tuning the frequency
response and full scale range of the solution. For
applications with unique vibration environments,
contact the factory for more information.
Note 9: The actual delay time for the triggering of the fault condition (high impedance output) can vary from a minimum of 2.3 sec to a maximum of
5.7 seconds, depending on the state of the internal signal processing when the fault condition is first detected. Note this is not to be confused with
the Tip-Over delay, which is based on the 3Hz Output Data Rate (ODR) of the device (thus tip-over would be reflected on the OUT pin within 1-2
clock cycles (330 – 670ms).
MEMSIC MXC6240/41AU Rev.A (6/27/2016)
Page 4 of 6
Formal release date: 8/18/2016
CIRCUIT SCHEMATICS
REFLOW PROFILE
Notes:
Reflow is limited to two cycles.
If a second reflow cycle is implemented, it should be
applied only after device has cooled down to 25℃
(room temperature)
LANDING PATTERN
(Unit: mm)
Above is the reflow profile for Pb free process
The peak temperature on the sensor surface must be
limited to under 260℃ for 10 seconds. Follow solder
paste supplier’s recommendations for the best SMT
quality.
When soldering manually or repairing via soldering
iron for the accelerometer, the time must be limited to
less than 10 seconds and the temperature must not
exceed 275 . If a heat gun is used, the time must be
limited to less than 10seconds and the temperature
must not exceed 270
Avoid bending the PCB after sensor assembly
3
1.8
35
0.
R
1 OUT
1.15
6 GND
0.6
0.7
3
2 P2
3 VDD
0.3
1.2
1.2
5 P0
4 P1
MEMSIC MXC6240/41AU Rev.A (6/27/2016)
Page 5 of 6
Formal release date: 8/18/2016
