|Dimensions||1800μm x 1670μm|
As part of the PROXYST project, we have developed a transmitter/receiver front-end IC for a miniaturized ultrasound range finder for small distances 1 .. 10 cm. The range finder uses silicon membrane transducers fabricated in standard CMOS technology, to generate or detect ultrasound waves at 90-100kHz. The system architecture allows the measurement of the distance using a novel delta f phase shift method and can be fully integarted in the same technology as used for the membrane.
The mixed-signal chip features all relevant functions to accomplish the measurement as well as to drive and read-out the silicon membranes. In receive mod, 72dB gain, AC coupled and low noise amplification of the sensor signals is performed.
As a transmitter, the IC excites the membrane thermally by applying a 100kHz, 1.5V AC signal superimposed with a DC voltage to a 100Ohm heater. The DC voltage is derived form a monotonic 12 bit D/A converter to set a self-calibrated, proper operating point for the membrane.
The IC also incorporates a band-gap cell fo the analog ground generator and a frequency synthesizer needed for the deltaf phase shift measurement.