ADIS16354AMLZ Analog Devices Inc, ADIS16354AMLZ Datasheet - Page 12

• Manufacturer Part Number: ADIS16354AMLZ
• Description: MODULE GYRO/ACCELEROMETER 24LD
• Manufacturer: Analog Devices Inc
• Series: iSensor™r

Specifications of ADIS16354AMLZ

• Output Type: Digital - SPI
• Sensor Type: Gyroscope and Accelerometer
• No. Of Axes: 3
• Sensor Case Style: ML-24-2
• No. Of Pins: 24
• Supply Voltage Range: 4.75V To 5.25V
• Operating Temperature Range: -40°C To +85°C
• Acceleration Range: ± 1.7g
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• For Use With: ADIS16354/PCBZ - BOARD EVAL FOR ADIS16354
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Not applicable / Not applicable

ADIS16354
THEORY OF OPERATION
OVERVIEW
The ADIS16354 integrates three orthogonal axes of gyroscope
sensors with three orthogonal axes of accelerometer sensors,
creating the basic six degrees of freedom (6DOF) in a single
package. The accelerometers are oriented along the axis of rota-
tion for each gyroscope. These six sensing elements are held
together by a mechanical structure that provides tight force and
motion coupling. Each sensor’s output signal is sampled using
an ADC, and then the digital data is fed into a proprietary
digital processing circuit. The digital processing circuit applies
the correction tables to each sensor’s output, manages the
input/output function using a simple register structure and
serial interface, and provides many other features that simplify
system-level designs.
GYROSCOPE SENSOR
The core MEMS angular rate sensor (gyroscope) used in the
ADIS16354 operates on the principle of a resonator gyroscope.
Two polysilicon sensing structures each contain a dither frame,
which is electrostatically driven to resonance. This provides the
velocity element required to produce a Coriolis force during
rotation. At two of the outer extremes of each frame, orthogonal
to the dither motion, are movable fingers, which are placed
between fixed 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.
ACCELEROMETER SENSOR
The core acceleration sensor used in the ADIS16354 is a surface
micromachined polysilicon structure built on top of the silicon
wafer. Polysilicon springs suspend the structure over the surface
of the wafer and provide a resistance against acceleration forces.
Deflection of the structure is measured using a differential
capacitor that consists of independent fixed plates and central
plates attached to the moving mass. Acceleration deflects the
beam and unbalances the differential capacitor, resulting in a
differential output that is fed to a series of gain and demodula-
tion stages that produce the electrical rate signal output.
FACTORY CALIBRATION
The ADIS16354 provides a factory calibration that simplifies
the process of integrating it into system-level designs. This
calibration provides correction for initial sensor bias and
sensitivity, power supply variation, temperature variation, axial
alignment, and linear acceleration (gyroscopes). An extensive,
three-dimensional characterization provides the basis for
generating correction tables for each individual sensor.
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CONTROL REGISTER STRUCTURE
The ADIS16354 provides configuration control to many critical
operating parameters by using a dual-memory register structure.
The volatile SRAM register locations control operation of the
part while the nonvolatile flash memory locations preserve the
configuration settings. Updating a register’s contents only affects
its SRAM location. Preserving the updates in its corresponding
flash memory location requires initiation of the flash update
command. This helps reduce the number of write cycles to the
flash memory and consequently increases the endurance of the
flash memory. During startup and reset-recovery sequences, the
flash memory contents are automatically loaded into the SRAM
register locations.
AUXILIARY ADC FUNCTION
The auxiliary ADC function integrates a standard 12-bit ADC
into the ADIS16354 to digitize other system-level analog signals.
The output of the ADC can be monitored through the AUX_ADC
register, as defined in Table 7. The ADC is a 12-bit successive
approximation converter. The output data is presented in
straight binary format with the full-scale range extending from
0 V to 2.5 V.
Figure 26 shows the equivalent circuit of the analog input struc-
ture of the ADC. The input capacitor (C1) is typically 4 pF and
can be attributed to parasitic package capacitance. The two diodes
provide ESD protection for the analog input. Care must be taken to
ensure that the analog input signals are never outside the range
of −0.3 V to +3.5 V. Signals outside this range causes the diodes
to become forward-biased and to start conducting. The diodes
can handle 10 mA without causing irreversible damage. The
resistor is a lumped component that represents the on resistance
of the switches. The value of this resistance is typically 100 Ω.
Capacitor C2 represents the ADC sampling capacitor and is
typically 16 pF.
For ac applications, removing high frequency components from
the analog input signal is recommended by the use of a low-pass
filter on the analog input pin.
In applications where harmonic distortion and signal-to-noise
ratios are critical, the analog input must be driven from a low
impedance source. Large source impedances significantly affect
the ac performance of the ADC. This can necessitate the use of
an input buffer amplifier. When no input amplifier is used to drive
the analog input, the source impedance should be limited to
values lower than 1 kΩ.
Figure 26. Equivalent Analog Input Circuit
Conversion Phase: Switch Open
C1
Track Phase: Switch Closed
VDD
D
D
R1
C2