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ADXRS300 Arkusz danych(PDF) 5 Page - Analog Devices |
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ADXRS300 Arkusz danych(HTML) 5 Page - Analog Devices |
5 / 8 page ADXRS300 Rev. A | Page 5 of 8 THEORY OF OPERATION The ADXRS300 operates on the principle of a resonator gyro. Two polysilicon sensing structures each contain a dither frame, which is electrostatically driven to resonance. This produces the necessary velocity element to produce a Coriolis force during angular rate. At two of the outer extremes of each frame, orthogonal to the dither motion, are movable fingers that are placed between fixed pickoff fingers to form a capacitive pickoff structure that senses Coriolis motion. The resulting signal is fed to a series of gain and demodulation stages that produce the electrical rate signal output. The dual-sensor design rejects external g-forces and vibration. Fabricating the sensor with the signal conditioning electronics preserves signal integrity in noisy environments. The electrostatic resonator requires 14 V to 16 V for operation. Since only 5 V is typically available in most applications, a charge pump is included on-chip. If an external 14 V to 16 V supply is available, the two capacitors on CP1–CP4 can be omit- ted and this supply can be connected to CP5 (Pin 7D) with a 100 nF decoupling capacitor in place of the 47 nF. After the demodulation stage there is a single-pole low-pass filter consisting of an internal 7 kΩ resistor (RSEN1) and an external user-supplied capacitor (CMID). A CMID capacitor of 100 nF sets a 400 Hz ±35% low-pass pole and is used to limit high frequency artifacts before final amplification. Bandwidth limit capacitor, COUT, sets the pass bandwidth (see Figure 4 and the Setting Bandwidth section). AGND TEMP ST2 ST1 CP1 CP2 RATEOUT CP4 PDD CMID SUMJ 2.5V 6A 5A 4A 3A 2A 1B 1C 1D 1E 1F 7B 7C 7D 7E 7F 6G 5G 4G 3G 2G CP5 CP3 100nF COUT = 22nF 22nF AVCC 100nF 100nF PGND 22nF 47nF 5V NOTE THAT INNER ROWS/COLUMNS OF PINS HAVE BEEN OMITTED FOR CLARITY BUT SHOULD BE CONNECTED IN THE APPLICATION. Figure 3. Example Application Circuit (Top View) Supply and Common Considerations Only power supplies used for supplying analog circuits are rec- ommended for powering the ADXRS300. High frequency noise and transients associated with digital circuit supplies may have adverse effects on device operation. Figure 3 shows the recommended connections for the ADXRS300 where both AVCC and PDD have a separate decoupling capacitor. These should be placed as close to the their respective pins as possible before routing to the system analog supply. This will minimize the noise injected by the charge pump that uses the PDD supply. It is also recommended to place the charge pump capacitors connected to the CP1–CP4 pins as close to the part as possible. These capacitors are used to produce the on-chip high voltage supply switched at the dither frequency at approximately 14 kHz. Care should be taken to ensure that there is no more than 50 pF of stray capacitance between CP1–CP4 and ground. Surface-mount chip capacitors are suitable as long as they are rated for over 15 V. 5V + - SELF TEST AVCC ST1 ST2 3A 5G 4G ADXRS300 CP2 CP1 PDD 4A 5A 7E 6G CHARGE PUMP/REG. 12V PTAT 7F 6A 7B 7C 7D 47nF CP4 CP3 CP5 RATE SENSOR 2G 1F 1D CORIOLIS SIGNAL CHANNEL AGND CMID 1C SUMJ RATE- OUT 2.5V 1B 2A 1E 3G TEMP ROUT 180k Ω 1% RESONATOR LOOP DEMOD π 2.5V REF ≈7kΩ±35% 100nF 22nF 100nF 100nF COUT RSEN1 RSEN2 22nF PGND Figure 4. Block Diagram with External Components Setting Bandwidth External capacitors CMID and COUT are used in combination with on-chip resistors to create two low-pass filters to limit the bandwidth of the ADXRS300’s rate response. The –3 dB fre- quency set by ROUT and COUT is ( ) OUT OUT OUT C R π / f × × × = 2 1 and can be well controlled since ROUT has been trimmed during manufacturing to be 180 kΩ ±1%. Any external resistor applied |
Podobny numer części - ADXRS300 |
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Podobny opis - ADXRS300 |
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