Features

* Three -axis induction

* Small and low -key packaging

* 4mm × 4mm × 1.45 mm LFCSP

* Low power consumption: Typical 350μA

* Single power operation: 1.8 V to 3.6 V v

* 10000 grams of electric shock survival

* Excellent temperature stability

* Each axis per shaft Bandwidth adjustment with a capacitor

* meets the ROHS/Weee lead standard

Application

* cost sensitive, low in cost, low Application of power consumption, sports and tilt sensors

* Mobile device

* Game system

*[ 123] Disk drive protection

*

Stability of the image

sports and health equipment

] ADXL325

is a small, low -power, complete three -axis acceleration meter with signal adjustment voltage output. The minimum full -scale range of the product measurement acceleration is ± 5G. It can measure the static gravity acceleration in the application of tilt sensing, and dynamic acceleration caused by motion, impact or vibration.

The user uses the bandwidth of the acceleration meter on the CX, CY, and CZ capacitors on the Xout, YouT, and ZOUT pins. You can choose applications suitable for the range of 0.5 Hz to 1600 Hz and the z axis that are suitable for X and Y axis to 0.5 Hz to 550 Hz.

ADXL325 has 4 mm × 4 mm × 1.45 mm, 16 lead, plastic lead frame chip size packaging (LFCSP_LQ) and other small -sized products.

Function box diagram

pin configuration and function description

Typical performance features

n gt; 1000, unless there is another explanation.

Operation theory

adxl325 is a complete three -axis acceleration measurement system. Minimum measurement of adxl325The range is ± 5 g. It contains polysilicon surface micro -mechanical sensors and signal conditioning circuits to realize the measuring architecture of the opening of the ring. The output signal is an analog voltage proportional to the acceleration. The acceleration meter can measure the static acceleration of the gravity in the application of the tilt sensor, and the dynamic acceleration generated by the movement, impact or vibration.

This sensor is a polysilicon surface micro -mechanical structure, built on a silicon wafer. The polycrystalline silicon spring hangs the structure on the wafer surface and provides resistance to acceleration. The deflection of the structure is measured with a differential capacitor. The capacitor consists of an independent fixed plate and a board attached to the mobile quality. The fixed board is driven by 180 ° different phase wave. The acceleration makes the movement of the movement, and the differential capacitor loses a balance, which generates a sensor output that generates an amplitude and acceleration. Then use phase sensitive demodulation technology to determine the acceleration and direction.

The output of the demodulator is enlarged and brought away from the chip through a 32 kΩ resistor. The user then adds a capacitor to set the signal bandwidth of the device. This filter can improve measurement resolution and help prevent confusion.

Mechanical sensor

ADXL325 uses a single structure to sense X, Y, and Z axis. Therefore, the three -axis sensing direction is highly positive, and the sensitivity of the cross -axis is very low. The mechanical deviation of sensor mold and packaging is the main source of the sensitivity of cross -axis. Of course, the mechanical deviation can be calibrated at the system level.

Performance

Innovative design technology ensures that ADXL325 has built -in high performance, rather than using additional temperature compensation circuits. As a result, there is no quantization error nor non-monotonous behavior, and the temperature lag is very low (usually within the temperature range of -25 ° C to+70 ° C lt; 3 mg).

Application information

Power supply decoupling

For most applications, a 0.1 μF capacitor CDS is placed near the ADXL325 power pins, which can fully accelerate meter meter meter meter meter meter meter meter meter meter meter meter meter meter meter meter meter meter measuring the acceleration meter full meter meter meter meter meter meter meter meter meter meter meter meter fully meter metering Separation from noise on the power supply. However, in applications with noise in the internal clock frequency (or any harmonic) in the 50 kHz, you need to pay attention to the power bypass, because this noise may cause the acceleration measurement error. If you need extra decoupling, you can insert a 100Ω (or smaller) resistor or iron oxygen magnetic beads on the power line. In addition, you can add larger large -capacity bypass containers (1 μF or larger) to CDS. Make sure that the connection from ADXL325 to the power supply is low impedance, because the noise transmitted through grounding has a similar effect with the noise transmitted through VS.

Use C, C, and C to set the Z axis with bandwidth ten

ADXL325 to have regulations that restrict the frequency band of XOUT, YouT, and ZOUT pins. Capacors must be added to these feet to achieve low -pass filtering to eliminate hybrids and noise. 3DB bandwidthThe equation is:

or simpler

The tolerance of the internal resistor (RFILT) usually changes to its standard The ± 15%of the value (32 kΩ), the bandwidth also changed accordingly. In all cases, the minimum capacitance of CX, CY and CZ is 0.0047μF.

Self -test

ST pin control self -test function. When the pin is set to V, the static power is applied to the acceleration beam. As a result, the beam movement allows users to test whether the acceleration meter works properly. The typical changes of the output are -1.08 g (corresponding to -190 MV) on the X axis, +1.08 g (+190 mv) on the Y axis, and +1.83 g (+320 mv) on the Z axis. When using it normally, this ST pin can keep the road or connect to the public (COM).

Do not expose the ST pin to a voltage greater than V+0.3 V. If this is not guaranteed due to the system design (for example, multiple power voltage) cannot be guaranteed, it is recommended to use a low V clamp diode between ST and V.

Design weighing of the characteristics of the filter: noise/bw weighing

Selected acceleration meter bandwidth finally determines the measurement resolution (minimum detection acceleration). Filter can reduce the noise floor and improve the resolution of the acceleration meter. The resolution depends on the simulation filter bandwidth at the X, Y and Z.

The output of ADXL325 has a typical bandwidth greater than 500Hz. The user must filter the signal at this time to limit the overlapping error. The simulation bandwidth shall not exceed half of the frequency of the simulation to the digital sampling, and minimize it. It can further reduce the simulation bandwidth to reduce noise and increase resolution.

ADXL325 noise has the characteristics of white high noise. At all frequencies, the contribution of white Gaos noise is equal, and it is described by μg/√Hz (the square root of the noise and acceleration meter bandwidth). Users should limit the bandwidth to the minimum frequency required by the application to maximize the resolution and dynamic range of the acceleration meter.

Using the single -pole rolling characteristics, the typical noise of ADXL325 is:

The peak of noise is usually required. The noise in the peak can only be estimated by statistical methods. Table 5 helps to estimate the probability of exceeding various peak values when a given average root value.

Use working voltage other than 3V

ADXL325 is tested and specified under V 3V; however, it can be used as low as 1.8V or Gundam. 3.6V voltage power supply. Please note that some performance parameters change as the power supply voltage changes.

adxl325The output is measured by ratio; therefore, the output sensitivity (or proportional factor) varies with the power supply voltage. When V 3.6 V, the output sensitivity is usually 209 MV/g. When V 2 V, the output sensitivity is usually 116 mv/g.

Zero -G bias output is also the ratio output; therefore, zero G output is nominally equal to V/2 under all power supply voltage.

The output noise is not measured, but the absolute value of the volt as a unit; therefore, the noise density decreases as the power supply voltage increases. This is because when the noise voltage remains constant, the marking factor (MV/G) increases. When V 3.6V, the X -axis and Y -axis noise density is usually 200 μg/√Hz, and when V 2V, the X -axis noise density is usually 300 μg/√Hz.

Self -test response (G) is generally proportional to the square of the power supply voltage. However, when the amount of sensitivity is combined with the power supply voltage, the self -test response of volt -in -units is roughly proportional to the cube of the power supply voltage.

For example, when V 3.6 V, ADXL325 is about -328 MV for the X axis, the Y axis is about +328 MV, and the Z axis is about +553 MV. When V 2 V, the self-propelled response of the X axis is about -56 MV, the Y axis is +56 MV, and the Z axis is -95 MV.

As the power supply voltage decreases, the power supply current decreases. The typical current of V 3.6V consumes 375 μA, and the typical current consumption of 300 μA when V 2V is 300 μA.

Layout and design recommendations

The recommended welding shape is shown in Figure 25, and then the description of the characteristics of the shape in Table 6. The recommended PCB layout or welding ring diagram is shown in Figure 26.