MXA6500MP中文资料

Low Cost, Low Noise ±1 g

Dual Axis Accelerometer with Absolute Analog Outputs

MXA6500G/M

FEATURES

Low cost

Resolution better than 1 milli-g

Dual axis accelerometer fabricated on a monolithic CMOS IC

On chip mixed signal processing

No moving parts; >50,000 g shock survival rating 5mm X 5mm X 1.55mm LCC package

2.7V to

3.6V single supply continuous operation Compensated for Sensitivity over temperature Ultra low initial Zero-g Offset

No adjustment needed outside APPLICATIONS

Tilt and motion sensing in cost-sensitive applications Smart handheld devices

Computer security

Input devices

Pedometers and activity monitors

Gaming controllers

No

Connection

No

Connection

Xout

Yout MXA6500G/M FUNCTIONAL BLOCK DIAGRAM

Toys and entertainment products

GENERAL DESCRIPTION

The MXA6500G/M is a low cost, dual axis accelerometer fabricated on a standard, submicron CMOS process. It is a complete sensing system with on-chip mixed signal processing. The MXA6500G/M measures acceleration with a full-scale range of ±1 g and a sensitivity of 500mV/g @3V at 25°C. It can measure both dynamic acceleration (e.g. vibration) and static acceleration (e.g. gravity). The MXA6500G/M design is based on heat convection and requires no solid proof mass. This eliminates stiction and particle problems associated with competitive devices and provides shock survival greater than 50,000 g, leading to significantly lower failure rate and lower loss due to handling during assembly and at customer field application. The max noise floor is 1 m g/Hz allowing signals below 1 milli-g to be resolved at 1 Hz bandwidth.The MXA6500G/M is packaged in a hermetically sealed LCC surface mount package (5 mm x 5 mm x 1.55 mm height).

It is operational over a -40°C to 85°C(M) and 0°C to 70°C(G) temperature range.

Information furnished by MEMSIC is believed to be accurate and reliable. However, no responsibility is assumed by MEMSIC for its use, nor 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. ?MEMSIC, Inc.

800 Turnpike St., Suite 202, North Andover, MA 01845 Tel: 978.738.0900 Fax: 978.738.0196 https://www.wendangku.net/doc/c61820904.html,

MXA6500G/M SPECIFICATIONS(Measurements @ 25°C, Acceleration = 0 g unless otherwise noted; V DD = 3.0V unless otherwise specified)

NOTES

1 Guaranteed by measurement of initial offset and sensitivity.

2 Alignment error is specified as the angle between the true and indicated axis of

sensitivity.

3 Cross axis sensitivity is the algebraic sum of the alignment and the inherent

sensitivity errors.

4 Defined as the output change from ambient to maximum temperature or ambient to

minimum temperature.

5 Output settled to within ±17mg.

ABSOLUTE MAXIMUM RATINGS*

Supply Voltage (V DD) ………………...-0.5 to +7.0V

Storage Temperature ……….…………-65°C to +150°

C

Acceleration ……………………………………..50,000 g

*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 device reliability.

Pin Description: LCC-8 Package

Pin Name Description

1 PD Power Down Control

2 TP Connect to ground

3 COM Common

4 NC Do Not Connect

5 NC Do Not Connect

6 Yout Y Channel Output

7 Xout X Channel Output

8 V DD 2.7V to 3.6V

Ordering Guide

Model Package

Style Temperature

Range

MXA6500GP

LCC8

RoHS compliant 0 to +70°C

MXA6500MP

LCC8

RoHS compliant -40 to 85°C

MXA6500GB LCC8, Pb-free 0 to +70°C MXA6500MB LCC8, Pb-free -40 to 85°C

away from the +X direction following the right-hand rule. Small circle indicates pin one(1) THEORY OF OPERATION

The MEMSIC device is a complete dual-axis acceleration measurement system fabricated on a monolithic CMOS IC process. The device operation is based on heat transfer by natural convection and operates like other accelerometers having a proof mass. The proof mass in the MEMSIC sensor is a gas.

A single heat source, centered in the silicon chip is suspended across a cavity. Equally spaced

aluminum/polysilicon thermopiles (groups of thermocouples) are located equidistantly on all four sides of the heat source (dual axis). Under zero acceleration, a temperature gradient is symmetrical about the heat source, so that the temperature is the same at all four thermopiles, causing them to output the same voltage.

PIN DESCRIPTIONS

V DD – This is the supply input for the circuits and the sensor heater in the accelerometer. The DC voltage should be between 2.7 and 3.6 volts. Refer to the section on PCB layout and fabrication suggestions for guidance on external parts and connections recommended.

COM– This is the ground pin for the accelerometer.

TP- This pin should be connected to the ground.

Xout – This pin is the output of the x-axis acceleration sensor. The user should ensure the load impedance is sufficiently high as to not source/sink >100μA typical. While the sensitivity of this axis has been programmed at the factory to be the same as the sensitivity for the y-axis, the accelerometer can be programmed for non-equal sensitivities on the x- and y-axes. Contact the factory for additional information.

Yout – This pin is the output of the y-axis acceleration sensor. The user should ensure the load impedance is sufficiently high as to not source/sink >100μA typical. While the sensitivity of this axis has been programmed at the factory to be the same as the sensitivity for the x-axis, the accelerometer can be programmed for non-equal sensitivities on the x- and y-axes. Contact the factory for additional information.

PD – Pin 1 is the power down control pin. Pull this pin HIGH will put the accelerometer into power down mode. When the part goes into power down mode, the total current will be smaller than 0.1uA at 3V.

In normal operation mode, this pin should be connected to Ground.

DISCUSSION OF TILT APPLICATIONS AND RESOLUTION

Tilt Applications: One of the most popular applications of the MEMSIC accelerometer product line is in

tilt/inclination measurement. An accelerometer uses the force of gravity as an input to determine the inclination angle of an object.

A MEMSIC accelerometer is most sensitive to changes in position, or tilt, when the accelerometer’s sensitive axis is perpendicular to the force of gravity, or parallel to the Earth’s surface. Similarly, when the accelerometer’s axis is parallel to the force of gravity (perpendicular to the Earth’s surface), it is least sensitive to changes in tilt.

Following table and figure help illustrate the output changes in the X- and Y-axes as the unit is tilted from +90°to 0°. Notice that when one axis has a small change in output per degree of tilt (in m g), the second axis has a large change in output per degree of tilt. The complementary nature of these two signals permits low cost accurate tilt

sensing to be achieved with the MEMSIC device (reference

X-Axis

Y-Axis X-Axis

Orientation

To Earth’s

Surface

(deg.)

X Output

(g)

Change

per deg.

of tilt

(m g)

Y Output

(g)

Change

per deg.

of tilt

(m g)

90 1.000 0.15 0.000

17.45

85 0.996 1.37 0.087

17.37

80 0.985 2.88 0.174

17.16

70 0.940 5.86 0.342

16.35

60 0.866 8.59 0.500

15.04

45 0.707 12.23 0.707

12.23

30 0.500 15.04 0.866 8.59

20 0.342 16.35 0.940 5.86

10 0.174 17.16 0.985 2.88

5 0.087 17.37 0.99

6 1.37

0 0.000 17.45 1.000 0.15

Changes in Tilt for X- and Y-Axes

Resolution: The accelerometer resolution is limited by

noise. The output noise will vary with the measurement

bandwidth. With the reduction of the bandwidth, by

applying an external low pass filter, the output noise drops.

Reduction of bandwidth will improve the signal to noise

ratio and the resolution. The output noise scales directly

with the square root of the measurement bandwidth. The

maximum amplitude of the noise, its peak- to- peak value, approximately defines the worst case resolution of the measurement. With a simple RC low pass filter, the rms

noise is calculated as follows:

Noise (mg rms) = Noise(mg/Hz) * )6.1*)

(

(Hz

Bandwidth

The peak-to-peak noise is approximately equal to 6.6 times

the rms value (for an average uncertainty of 0.1%).

POWER SUPPLY NOISE REJECTION

One capacitor is recommended for best rejection of power

supply noise (reference figure below). The capacitor should

be located as close as possible to the device supply pin

(V DD). The capacitor lead length should be as short as

possible, and surface mount capacitor is preferred. For

PCB LAYOUT AND FABRICATION SUGGESTIONS 1. It is best to connect a 0.1uF capacitor directly across

V DD and COM pin.

2. Robust low inductance ground wiring should be used.

3. Care should be taken to ensure there is “thermal

symmetry” on the PCB immediately surrounding the

MEMSIC device and that there is no significant heat

source nearby.

4. A metal ground plane should be added directly beneath

the MEMSIC device. The size of the plane should be

similar to the MEMSIC device’s footprint and be as

thick as possible.

5. Vias can be added symmetrically around the ground

plane. Vias increase thermal isolation of the device

from the rest of the PCB.