 Products & Services > Intellectual Property >MEMS Microphone Interface
Cordoba is a complete interface circuit for capacitive MEMS microphones. It consists of an input operational transconductance amplifier (OTA), and a 3rd order continuous-time sigma-delta modulator (SDM). The OTA presents high input impedance to the microphone and act as a pre-amplifier. It has a programmable gain in the range of 0-25dB in order to accommodate different microphone types with different sensitivities and also microphones with built-in amplifier stages.
The system also includes a charge pump (CP) to provide biasing to the microphone in the range of 7-14V with very low ripple of 1Vpp. Two low drop-out regulators (LDO) are used to generate a constant 1.3V for the CP and the rest of the analog circuitry. The design provides an internally generated clock. It can also support an external crystal. Two modes of operation are available : full speed mode at a nominal clock rate of 5MHz that supports 20kHz signal BW for high fidelity audio applications and a half speed mode at a nominal clock rate of 2.5MHz that supports 12kHz signal BW with low power consumption. Cordoba has a high SNR and a high sensitivity, making it an excellent choice for far field applications. The design is implemented in 130nm CMOS technology. It consumes 1.2mA for the full speed mode and occupies an area of 0.27mm².
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Features
- Interfaces directly with the MEMS microphone and provides digital output and microphone bias.
- System includes 3rd order ΣΔ modulator with 20dB programmable gain, and a CP for microphone bias.
- High audio quality with dynamic range of 89dBA for 20kHz signal BW.
- Accommodates different MIC vendors with programmable gain and bias voltage
- Highly integrated with reduced off-chip components
- THD < 1% and < 10% for 50mVpp and 250mVpp input signal, respectively.
- Low current consumption < 1.2mA
- Operate with a battery voltage from 1.5-3.6V
- Small area of ~0.27mm2 in 0.13µ CMOS
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