Datasheet ADIS16260, ADIS16265 (Analog Devices) - 9

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Data Sheet ADIS16260/ADIS16265 THEORY OF OPERATION
The ADIS16260 and ADIS16265 integrate a MEMS gyroscope
USER INTERFACE
with data sampling, signal processing, and calibration functions,
SPI Interface
along with a simple user interface. This sensing system collects Data collection and configuration commands both use the SPI, data autonomously and makes it available to any processor system which consists of four wires. The chip select (CS) signal activates that supports a 4-wire serial peripheral interface (SPI). the SPI interface, and the serial clock (SCLK) signal synchronizes
SENSING ELEMENT
the serial data lines. The serial input data clocks into DIN on The sensing element operates on the principle of a resonator the SCLK rising edge, and the serial output data clocks out of gyro. Two polysilicon sensing structures each contain a dither DOUT on the SCLK falling edge. Many digital processor plat- frame that is electrostatically driven to resonance, producing forms support this interface with dedicated serial ports and the necessary velocity element to produce a Coriolis force simple instruction sets. during angular rate. At two of the outer extremes of each frame,
User Registers
orthogonal to the dither motion, movable fingers are placed The user registers provide addressing for all input/output between fixed pickoff fingers to form a capacitive pickoff operations on the SPI interface. Each 16-bit register has its structure that senses Coriolis motion. The resulting signal is fed own unique bit assignment and has two 7-bit addresses: one into a series of gain and demodulation stages that produce the for its upper byte and one for its lower byte. Table 7 provides electrical rate signal output. The differential structure minimizes a memory map of the user registers, along with the function of the response to linear acceleration (gravity, vibration, and so each register. on) and to EMI. The control registers use a dual memory structure. The SRAM
DATA SAMPLING AND PROCESSING
controls operation while the part is on and facilitates all user The ADIS16260 and ADIS16265 run autonomously, based on configuration inputs. The flash memory provides nonvolatile the configuration in the user control registers. The analog storage for control registers that have flash backup (see Table 7). gyroscope signal feeds into an analog-to-digital converter Storing configuration data in the flash memory requires a separate (ADC) stage, which passes digitized data into the controller for command (GLOB_CMD[3] = 1, DIN = 0xBE08). When the data processing and register loading. Data processing in the device powers on or resets, the flash memory contents are embedded controller includes correction formulas, filtering, loaded into the SRAM, and the device then starts producing and checking for preset alarm conditions. The correction formulas data according to the configuration in the control registers. are unique for each individual ADIS16260/ADIS16265 and come from the factory characterization of each device over a
MANUAL FLASH
temperature range of −40°C to +85°C.
BACKUP NONVOLATILE VOLATILE FLASH MEMORY SRAM MEMS OUTPUT SENSOR REGISTERS S (NO SPI ACCESS) SPI ACCESS L A N T T STARTUP G TEMP R R ADC OR RESET
8
O CONTROLLER O SI
00
SENSOR
6-
I P I P
24
SPI
08
SP CONTROL SP REGISTERS
Figure 8. SRAM and Flash Memory Diagram
AIN SIGNALS
7
CLOCK
00 6- 24 08 Figure 7. Simplified Sensor Signal Processing Diagram Rev. E | Page 9 of 20 Document Outline Features Applications General Description Functional Block Diagram Table of Contents Revision History Specifications Timing Specifications Timing Diagrams Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Theory of Operation Sensing Element Data Sampling and Processing User Interface SPI Interface User Registers Basic Operation SPI Write Commands SPI Read Commands Memory Map Processing Sensor Data Operational Controls Internal Sample Rate Sensor Bandwidth Digital Filtering Dynamic Range Calibration Global Commands Power Management Input/Output Functions General-Purpose I/O Data Ready I/O Indicator Auxiliary DAC Diagnostics Self-Test Memory Test Status Alarm Registers Product Identification Applications Information Assembly Bias Optimization Interface Printed Circuit Board (PCB) Outline Dimensions Ordering Guide