ISZ-500 Single-Axis Z-Gyroscope

Product Specification

PS-ISZ-0500B-00-03

Release Date: 07/08/09

CONFIDENTIAL & PROPRIETARY

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6.5

Coriolis Sense

Rotating the sensor about the Z-axis results in a Coriolis force on the Z-rate sensor. The Coriolis force

causes the mechanical structure to vibrate in-plane. The resulting vibration is detected by measuring the

capacitance change between the mechanical structure and fixed electrodes. This signal is converted to a

voltage waveform by means of low-noise charge integrating amplifier and amplification stages.

6.6

Demodulator

The output of the Coriolis sense is an amplitude modulated waveform. The amplitude corresponds to the

rotation rate, and the carrier frequency is the mechanical drive frequency. The synchronous demodulator

converts the Coriolis sense waveform to the low-frequency, angular rate signal.

6.7

Low-Pass Filter

After the demodulation stage, there is a low-pass filter. This filter attenuates noise and high frequency

artifacts before final amplification.

6.8

Auto Zero

The Auto Zero function is used to reduce DC offset caused by bias drift. The implementation of this function

will vary by application requirement. Pin 24 (AZ) is used to set the Auto Zero function, resetting the bias to

approximately VREF.

6.9

Temperature Sensor

A built-in Proportional-To-Absolute-Temperature (PTAT) sensor provides temperature information on Pin 23.

6.10 Charge Pump

The on-chip charge pump generates the voltage required to oscillate the mechanical structure.

6.11 Memory Trim

The on-chip memory is used to select the gyro’s sensitivity, calibrate the sensitivity, null DC offsets and

select the low-pass filter option

6.12 Scale Factor

The Rate-Out of the gyro is not ratiometric to the supply voltage. The scale factor is calibrated at the factory

and is nominally independent of supply voltage.

6.13 Reference Voltage

The gyro includes a bandgap reference circuit. The output voltage is typically 1.35V and is nominally

independent of temperature. The zero-rate signal is nominally equal to the reference value.

6.14 Analog Outputs

The ISZ-500 gyro has two Z-outputs (Z-OUT and Z4.5OUT), with scale factors and full-scale sensitivities that

vary by a factor of 4.5, as detailed in Section 8.2.7.

Having two sensitivities and two full-scale ranges for the one axis allows the end user to have one output that

can be used for faster motions (over a full scale range of ±500º/sec), and a second output that can be used

for slower motions (over a full scale range of ±110º/sec). Thus a lower-resolution analog-to-digital converter

(ADC) may be used to digitize the motion, with the gain of 4.5 in the Z4.5OUT output effectively giving the

user additional two-plus bits of resolution.