MEMS microphone with improved sensitivity
View Patent ↗A MEMS microphone with an improved sensitivity, e.g., a reduced temperature dependence of the sensitivity. The microphone includes a MEMS capacitor, a charging circuit and a bias circuit. The bias circuit includes a closed loop control circuit and creates a bias voltage with a temperature dependence.
1. MEMS microphone with improved sensitivity, comprising
a MEMS capacitor with a variable capacitance,
a charging circuit provided for charging the MEMS capacitor,
a bias circuit provided for creating a bias voltage V bias applied to the charging circuit, where
the bias circuit comprises a closed loop control circuit and
the bias voltage V bias has a temperature dependence.
2. MEMS microphone according to claim 1 , where the bias voltage V bias has a piecewise linear temperature dependence.
3. MEMS microphone according to claim 1 , where the closed loop control circuit comprises a temperature sensor.
4. MEMS microphone according to claim 3 , where the temperature sensor provides a Proportional To Absolute Temperature (PTAT) voltage V sen .
5. MEMS microphone according to claim 1 , where the closed loop control circuit comprises a slope generator.
6. MEMS microphone according to claim 5 , where the slope generator comprises a comparator and a plurality of serial connections of a resistor and a switch.
7. MEMS microphone according to claim 1 , where the closed loop control circuit comprises a slope control circuit.
8. MEMS microphone according to claim 7 , where the slope control circuit comprises a plurality of comparators.
9. MEMS microphone according to claim 1 , where the charging circuit comprises a charge pump.
10. MEMS microphone according to claim 5 , where
the slope generator generates a linear voltage V sg and
a slope of V sg is mainly proportional to the negative slope of the temperature dependence of the sensitivity of the microphone, —S(T), at a given temperature.
11. MEMS microphone according to claim 1 , where the bias voltage is the sum of a plurality of voltages selected from a plurality of temperature independent voltages and temperature dependent voltages.
12. MEMS microphone according to claim 1 , where the bias circuit is a part of an ASIC of the MEMS microphone.
13. MEMS microphone according to claim 1 , further comprising a non-volatile memory element for storing linearity parameters.
14. MEMS microphone with improved sensitivity, comprising
a MEMS capacitor with a variable capacitance,
a charging circuit provided for charging the MEMS capacitor,
a bias circuit provided for creating a bias voltage V bias applied to the charging circuit, where
the bias circuit comprises a closed loop control circuit,
the bias voltage V bias has a temperature dependence, and where the bias voltage V bias has a piecewise linear temperature dependence.
15. MEMS microphone with improved sensitivity, comprising
a MEMS capacitor with a variable capacitance,
a charging circuit provided for charging the MEMS capacitor,
a bias circuit provided for creating a bias voltage V bias applied to the charging circuit, where
the bias circuit comprises a closed loop control circuit which comprises a slope generator, and
the bias voltage V bias has a temperature dependence.