Solving the quandary of MEMS in closed loop
The validation of a MEMS electronic loop (SENSOR + ASIC) can easily become a nightmare without appropriate means for ASIC specification and validation.
The Dummy MEMS is an electrical emulator of the mechanical sensor behavior in closed loop. The main issue for specifying it is to assess with the right accuracy each of its domains of equivalence with the sensor.
Key Objectives
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Performing system prototyping with the capability to emulate the physical signal being sensed
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Optimizing the ASIC design
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Validating the ASIC performances in closed loop
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Getting a MEMS electronic loop working in a single pass
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Operating over a range where the MEMS displays a linear behavior
Equivalence Domains for an accelerometer
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Electrical input to represent the external acceleration
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Feedback force consists in any combination of the following (treating separately or combining) : sensor linearization and activation, force Balance and compensation of process variations
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First resonance frequency in closed loop
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Sensor sensing capacitance
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Closed loop gain
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Second resonance frequency
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Parasitics resistance
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MEMS Thermal Noise
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…
The best way to design a purely electronic Testbench for the ASIC
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Specify the Dummy Sensor
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Perform simulations with the electronics
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Develop the Dummy Sensor
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Perform validation of the electronics with the Dummy Sensor
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Check the MEMS electronic loop with the real Sensor
Mechanics to Electronics Translation
The purpose is to translate the behavior of mechanics into the electronics domain through efficient modeling techniques.
The whole process makes sense as soon as the level of mechanical modeling allows a piecemeal construction using the EMBLEM library elements from an analysis of the geometries of the mechanical structure.
Similarly the electronic dummy is synthesized on a library of circuit models.
