Datasheet ADIS16334 (Analog Devices) - 10

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Data Sheet ADIS16334 THEORY OF OPERATION
The ADIS16334 is a six degree of freedom (6DOF) inertial sensing
DATA SAMPLING AND PROCESSING
system. This sensing system collects data autonomously and The analog signals from each inertial sensor feed into a mixed makes it available to any processor system that supports a 4-wire signal processing circuit, which includes buffering, analog serial peripheral interface (SPI). filtering, digital sampling, digital filtering, and calibration.
GYROSCOPES CALIBRATION
Angular rate sensing in the ADIS16334 begins with a MEMS The digital processing stage includes a correction function for gyroscope that operates on the principle of a resonator gyro. Two each accelerometer and gyroscope sensor. Each sensor within polysilicon sensing structures each contain a dither frame that each unit has unique correction formulas, which optimize their is electrostatically driven to resonance, producing the necessary bias and sensitivity accuracy over temperature and supply. The full, velocity element to produce a Coriolis force during angular rate. 6DOF characterization also enables an internal frame alignment, At two of the outer extremes of each frame, orthogonal to the which minimizes cross-axis sensitivity and simplifies frame dither motion, are movable fingers that are placed between alignment after system installation. fixed pickoff fingers to form a capacitive pickoff structure that senses Coriolis motion. The resulting signal is fed to a series of
USER INTERFACE
gain and demodulation stages that produce the electrical rate
SPI Interface
signal output. The dual-sensor design rejects external g-forces The user registers manage user access to both sensor data and and vibration. configuration inputs. Each 16-bit register has its own unique bit
ACCELEROMETERS
assignment and two addresses: one for its upper byte and one for Acceleration sensing in the ADIS16334 starts with a MEMS its lower byte. Table 8 provides a memory map for each register, accelerometer core on each axis, which provides a linear motion-to- along with its function and lower byte address. Each data col ection electrical transducer function. Tiny polysilicon springs to tether a and configuration command both use the SPI, which consists of movable structure to a fixed frame inside the sensor core. The four wires. The chip select (CS) signal activates the SPI interface springs and mass of the movable structure provide a dependable and the serial clock (SCLK) synchronizes the serial data lines. relationship between acceleration and physical displacement Input commands clock into the DIN pin, one bit at a time, on between them. The moving structure and fixed frame have the SCLK rising edge. Output data clocks out of the DOUT pin electrical plates in a balanced, differential capacitor network. on the SCLK falling edge. As a SPI slave device, the DOUT contents When experiencing dynamic or static acceleration, it causes a reflect the information requested using a DIN command. physical deflection, which causes an imbalance in the capacitive network. A modulation/de-modulation circuit translates the capacitor imbalance into a representative electrical signal.
MEMS FILTERING AND OUTPUT ADC SENSOR CALIBRATION REGISTERS T LS R A PO IGN CONTROLLER CONTROL I S SPI P REGISTERS S
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DIGITAL I/O
09362- Figure 9. Simplified Sensor Signal Processing Diagram Rev. B | Page 9 of 20 Document Outline Features Applications General Description Functional Block Diagram Revision History Specifications Timing Specifications Timing Diagrams Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Theory of Operation Gyroscopes Accelerometers Data Sampling and Processing Calibration User Interface SPI Interface Basic Operation Reading Sensor Data Burst Read Function Memory Map Output Data Registers Gyroscopes Accelerometers Internal Temperature Measurements Device Configuration Dual Memory Structure Digital Processing Configuration Sample Rate Input Clock Configuration Digital Filtering Dynamic Range Optimizing Accuracy Automatic Bias Correction Manual Bias Correction Restoring Factory Calibration Point-of-Percussion/Linear-g Compensation System Tools Global Commands General-Purpose I/O Data Ready I/O Indicator Self-Test Memory Test Status Device Identification Flash Memory Management Alarms Static Alarm Use Dynamic Alarm Use Alarm Reporting Alarm Example Applications Information ADIS16334/PCBZ Installation Mounting Approaches Outline Dimensions Ordering Guide