a Dual Axis Accelerometer Evaluation Board ADXL202EB GENERAL DESCRIPTION The ADXL202EB is a simple evaluation board that allows the user to quickly evaluate the performance of the ADXL202 dual axis ± 2 g accelerometer. Only three additional through-hole passive components must be added, depending on the bandwidth required in your application. The ADXL202EB has a 5-pin 0.1-inch spaced header for access to all power and signal lines that may be attached to a prototyping board (breadboard) or wired via a standard plug. Two holes are provided for mechanical attachment of the ADXL202EB to your application. CIRCUIT DESCRIPTION The schematic and parts list of the ADXL202EB are shown in Figure 1 and Table I respectively. The minimal application will require at least one resistor (RSET) added to the board to set the PWM period (T2). Analog bandwidth may be set by adding capacitors C2 and C3. Refer to the ADXL202 data sheet for a complete description of the operation of the accelerometer. ADXL202EB A VDD D XOUT C5 0.47F 1 RSET ADDED BY USER C3 ADDED BY USER C4 2200pF C YOUT E COM B ST C1 2200pF C2 ADDED BY USER Figure 1. ADXL202EB Schematic The part layout of the ADXL202EB is shown in Figure 2. The ADXL202EB has two factory- installed 2200 pF capacitors (C1 and C4) at XFILT and YFILT to satisfy the minimum filter capacitor specification of the ADXL202. Your application will likely require narrower bandwidth (and lower noise), in which case a throughhole capacitor may be added in parallel in the space provided at C2 and C3 respectively. When calculating the capacitance required to achieve the desired analog bandwidth do not forget to subtract the 2200 pF already on the PCB. The pinout description of the ADXL202EB is shown in Table II. SETTING THE PERIOD OF THE DUTY CYCLE MODULATOR The DCM period is set by RSET. Choose a value between 100 kΩ and 2 MΩ. See Table III for some typical RSET values. REV. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices 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 Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 2000 ADXL202EB Reference Value Function C1 C2 C3 C4 J1 R1 U1 2200 pF/25 V Added by User Added by User 2200 pF/25 V Connector Added by User ADXL202 XFILT. Sets X axis analog bandwidth along with C2 XFILT. Sets X axis analog bandwidth along with C1 YFILT. Sets Y axis analog bandwidth along with C4 YFILT. Sets Y axis analog bandwidth along with C3 All power and signal connection through J1 RSET. Sets the PWM period (T2) Dual axis ± 2g accelerometer C01939–0-6/00 (rev. 0) Table I. ADXL202EB Parts List Table II. ADXL202EB Pinout Description Pin Reference Pinout E B D C A GROUND SELF-TEST INPUT X AXIS DUTY CYCLE OUT Y AXIS DUTY CYCLE OUT +V SUPPLY (3 V dc to 5.25 V dc) C5 C1 C2 RSET U1 C4 C3 Table III. DCM Period vs. RSET Value T2 Period RSET 1 ms 2 ms 5 ms 10 ms 124 kΩ 248 kΩ 620 kΩ 1.24 MΩ J1 E B D C A Figure 2. ADXL202EB Part Layout (Top View) SPECIAL NOTES ON HANDLING Note that the ADXL202EB is not reverse polarity protected. Reversing the +V SUPPLY and Ground pins will damage the ADXL202. Table IV. Typical XFILT and YFILT Values vs. Bandwidth and Noise Performance Bandwidth RMS Noise 0.01 µF 0.047 µF 0.1 µF 0.47 µF 500 Hz 100 Hz 50 Hz 10 Hz 12.7 mg 7 mg 4.2 mg 2.3 mg Dropping the ADXL202EB on a hard surface may generate several thousand g of acceleration. Enough to damage the accelerometer. Please refer to the ADXL202 data sheet for information on shock survivability. PRINTED IN U.S.A. XFILT, YFILT SETTING THE ADXL202’s BANDWIDTH The ADXL202EB is supplied with the minimum specified XFILT and YFILT values installed. Your application will likely require a narrower bandwidth to improve noise performance. See Table IV for some typical capacitor values. –2– REV. 0