Granted Patent B1

US 8,680,894 · App. 13/787,621 · Granted Mar 25, 2014

Abstract

Claims (38)

1. A driver circuit to drive a micro-electro-mechanical system (MEMS) comprising:

a converter to convert a digital input value into a pulse-width modulated signal having a precise amplitude;

a low pass filter to extract an average DC component of the pulse-width modulated signal; and

an amplifier to amplify the average DC component to provide an output voltage to drive an electrode of the MEMS.

2. The driver circuit of claim 1 , wherein the converter includes a precision voltage reference circuit to set the amplitude of the pulse-width modulated signal.

3. The driver circuit of claim 2 , wherein the pulse-width modulated signal is output from a buffer circuit powered from the precision voltage reference circuit.

4. The driver circuit of claim 1 , wherein the amplifier includes a switch to selectively direct the output voltage to a first output or a second output, the first output to drive a first electrode of the MEMS and the second output to drive a second electrode of the MEMS.

5. The driver circuit of claim 4 , wherein the amplifier further includes a feedback circuit to provide a feedback signal derived from the selected one of the first output and the second output.

6. The driver circuit of claim 5 , wherein the amplifier has a non-inverting input to receive the average DC component and an inverting input to receive the feedback signal.

7. The driver circuit of claim 4 , wherein the switch selectively directs the output voltage to the first output or the second output responsive to a sign bit of the digital input value.

8. The driver circuit of claim 1 , further comprising:

an error compensator to generate the digital input value based on a digital target voltage value,

wherein the error compensator compensates for one or more of an offset error, a gain error, and a linearity error of the combined converter, low pass filter, and amplifier.

9. The driver circuit of claim 8 , wherein the error compensator comprises a memory storing compensation data.

10. The driver circuit of claim 9 , wherein the compensation data comprises a lookup table.

11. The driver circuit of claim 9 , wherein

the error compensator comprises a processor that derives the digital input value from the digital target voltage value based on an equation, and

the compensation data comprises one or more coefficients for use in the equation.

12. The driver circuit of claim 9 , wherein the compensation data is derived from measurements performed on the combined converter, low pass filter, and amplifier.

13. A method of driving a micro-electro-mechanical system (MEMS) device, comprising:

converting a digital input value into a pulse-width modulated signal having a precise amplitude;

filtering the pulse-width modulated signal to extract an average DC component;

amplifying the average DC component to provide an output voltage; and

driving an electrode of the MEMS device with the output voltage.

14. The method of claim 13 , wherein converting a digital input value into a pulse-width modulated signal having a precise amplitude comprises:

setting the amplitude of the pulse-width modulated signal with a precision voltage reference circuit.

15. The method of claim 14 , wherein setting the amplitude of the pulse-width modulated signal with a precision voltage reference circuit comprises:

outputting the pulse-width modulated signal from a buffer circuit powered from the precision voltage reference circuit.

16. The method of claim 13 , wherein amplifying the average DC component to provide an output voltage comprises:

selectively directing the output voltage to a first output or a second output, the first output coupled to a first electrode of the MEMS device and the second output coupled to a second electrode of the MEMS device.

17. The method of claim 16 , wherein selectively directing the output voltage to a first output or a second output comprises:

directing the output voltage to the first output or the second output responsive to a sign bit of the digital input value.

18. The method of claim 13 , further comprising:

compensating for one or more of an offset error, a gain error, and a linearity error of the combined converter, low pass filter, and amplifier.

19. The method of claim 18 , wherein compensating for one or more of an offset error, a gain error, and a linearity error comprises:

using a lookup table to convert a digital target voltage value into the digital input value.

20. The method of claim 18 , wherein compensating for one or more of an offset error, a gain error, and a linearity error comprises:

deriving the digital input value from a digital target voltage value based on an equation.

Assignments (6)