3 axis accelerometer and strain sensor readout MEMSbased
3 -axis accelerometer and strain sensor readout MEMS-based capacitive sensors Juan Santana Richard van den Hoven Imec-Holst Centre The Netherlands 1 st MEMSCON Event - 07 October 2010, Bucharest Imec- Holst Centre
Overview Summary • MEMS based charge sensing • Accelerometers & Strain sensors Technical Specifications • Programmable gain by timing control, sensitivity and accuracy read-out • Low-power • TSMC CMOS 0. 25 m with operating voltage (3. 0 V) • ± 2 g input range, 1 mg resolution • High linearity (1%) • Parasitics insensitive Applications • Accelerometers, strain sensors for structural assessment, automotive and BAN, industrial and healthcare 1 st MEMSCON Event - 07 October 2010, Bucharest Imec- Holst Centre
Architecture Novel Technique ü Integration of multiple pulses ü Variable gain set by number of pulses ü Integrated noise proportional to √N ü Timing allows duty-cycle control Architecture ü Signal-to-noise ratio control ü Decouples sensor from amplifier ü Allows readout of wide range of sensors ü Accurate sin(x)/x suppresses artifacts ü Multiplexed output Timing sequence 1 st MEMSCON Event - 07 October 2010, Bucharest Imec- Holst Centre
ASIC ESD System Level characteristics ü 3 -channel architecture Bias stage Y-channel ü 1 Analog multiplexed buffered output ü 1 Analog non-multiplexed (X channel) ü Synchronization signals available 4 mm X-channel ü Embedded filtering (sin(x)/x response) ü 1 Bias voltage (VDD) and 1 clock Z-channel ü Minimum capacitance ESD structures MUX+buffer +digital 2 mm 1 st MEMSCON Event - 07 October 2010, Bucharest Imec- Holst Centre
Results Accelerometer Variable sensitivity ~N Strain sensor Integrated Noise ~√N 1 st MEMSCON Event - 07 October 2010, Bucharest Imec- Holst Centre
Benchmarking Parameter Denison Paavola IMEC-NL Acceleration strain range ~± 1 g ISSCC 2008 ± 2 g Supply voltage Power Noise Floor 1. 7 -2. 2 V 1. 5µW 1 mg/√Hz 1. 0 V 1. 5µW 704µg/√Hz (accel. ) Non-linearity <1% --- Bandwidth FOM 10 Hz 1 Hz <1% (accelerometer) <0. 6% (strain sensor) 100 Hz F√(W/Hz) 8. 1× 10 -22 µW·µg/Hz Technology 1400 4. 41× 10 -20 881 0. 8µm CMOS 0. 25µm CMOS Area ---- 2. 25 mm² c 2 mm² (active) 8 mm 2 ± 2. 5 g ± 20, 000µe Variable gain 3. 0 V 15µW 70µg/√Hz State-of-the-art readout architectures 1 st MEMSCON Event - 07 October 2010, Bucharest Imec- Holst Centre
Conclusions ü Versatile architecture for MEMS-based capacitive sensors ü Cost effective design requires less external components ü Low Power ü Sampled output relaxes demands of following stages ü Embedded filtering ü Novel technique to control gain and SNR of the readout ü Can be extended to many other types of capacitive based sensors 1 st MEMSCON Event - 07 October 2010, Bucharest Company
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