Electronic Components Datasheet Search |
|
ADXL335 Datasheet(PDF) 7 Page - Analog Devices |
|
ADXL335 Datasheet(HTML) 7 Page - Analog Devices |
7 / 11 page Preliminary Technical Data ADXL335 Rev. PrA | Page 7 of 11 APPLICATIONS POWER SUPPLY DECOUPLING For most applications, a single 0.1 μF capacitor, CDC, placed close to the ADXL335 supply pins adequately decouples the accelerometer from noise on the power supply. However, in applications where noise is present at the 50 kHz internal clock frequency (or any harmonic thereof), additional care in power supply bypassing is required as this noise can cause errors in acceleration measurement. If additional decoupling is needed, a 100 Ω (or smaller) resistor or ferrite bead can be inserted in the supply line. Additionally, a larger bulk bypass capacitor (1 μF or greater) can be added in parallel to CDC. Ensure that the connection from the ADXL335 ground to the power supply ground is low impedance because noise transmitted through ground has a similar effect as noise transmitted through VS. SETTING THE BANDWIDTH USING CX, CY, AND CZ The ADXL335 has provisions for band limiting the XOUT, YOUT, and ZOUT pins. Capacitors must be added at these pins to implement low-pass filtering for antialiasing and noise reduction. The equation for the 3 dB bandwidth is F−3 dB = 1/(2π(32 kΩ) × C(X, Y, Z)) or more simply F–3 dB = 5 μF/C(X, Y, Z) The tolerance of the internal resistor (RFILT) typically varies as much as ±15% of its nominal value (32 kΩ), and the bandwidth varies accordingly. A minimum capacitance of 0.0047 μF for CX, CY, and CZ is recommended in all cases. Table 5. Filter Capacitor Selection, CX, CY, and CZ Bandwidth (Hz) Capacitor (μF) 1 4.7 10 0.47 50 0.10 100 0.05 200 0.027 500 0.01 SELF TEST The ST pin controls the self test feature. When this pin is set to VS, an electrostatic force is exerted on the accelerometer beam. The resulting movement of the beam allows the user to test if the accelerometer is functional. The typical change in output is −500 mg (corresponding to −150 mV) in the X-axis, 500 mg (or 150 mV) on the Y-axis, and −200 mg (or −60 mV) on the Z-axis. This ST pin may be left open circuit or connected to common (COM) in normal use. Never expose the ST pin to voltages greater than VS + 0.3 V. If this cannot be guaranteed due to the system design (for instance, if there are multiple supply voltages), then a low VF clamping diode between ST and VS is recommended. DESIGN TRADE-OFFS FOR SELECTING FILTER CHARACTERISTICS: THE NOISE/BW TRADE-OFF The selected accelerometer bandwidth ultimately determines the measurement resolution (smallest detectable acceleration). Filtering can be used to lower the noise floor to improve the resolution of the accelerometer. Resolution is dependent on the analog filter bandwidth at XOUT, YOUT, and ZOUT. The output of the ADXL335 has a typical bandwidth of greater than 500 Hz. The user must filter the signal at this point to limit aliasing errors. The analog bandwidth must be no more than half the analog-to-digital sampling frequency to minimize aliasing. The analog bandwidth can be further decreased to reduce noise and improve resolution. The ADXL335 noise has the characteristics of white Gaussian noise, which contributes equally at all frequencies and is described in terms of μg/√Hz (the noise is proportional to the square root of the accelerometer bandwidth). The user should limit bandwidth to the lowest frequency needed by the applica- tion to maximize the resolution and dynamic range of the accelerometer. With the single-pole, roll-off characteristic, the typical noise of the ADXL335 is determined by ) 1.6 ( × × = BW Density Noise Noise rms Often, the peak value of the noise is desired. Peak-to-peak noise can only be estimated by statistical methods. Table 6 is useful for estimating the probabilities of exceeding various peak values, given the rms value. Table 6. Estimation of Peak-to-Peak Noise Peak-to-Peak Value % of Time that Noise Exceeds Nominal Peak-to-Peak Value 2 × rms 32 4 × rms 4.6 6 × rms 0.27 8 × rms 0.006 USE WITH OPERATING VOLTAGES OTHER THAN 3 V The ADXL335 is tested and specified at VS = 3 V; however, it can be powered with VS as low as 1.8 V or as high as 3.6 V. Note that some performance parameters change as the supply voltage is varied. |
Similar Part No. - ADXL335 |
|
Similar Description - ADXL335 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |