Pseudo-differential accelerometer with high electromagnetic interference rejection

Patent metadata

Field	Value
Publication number	US-9116164-B2
Application number	US-201313788709-A
Country	US
Kind code	B2
Filing date	Mar 7, 2013
Priority date	Mar 7, 2013
Publication date	Aug 25, 2015
Grant date	Aug 25, 2015

Abstract

A pseudo-differential accelerometer resistant to EMI is disclosed that includes a device with a sensor core connected to an integrated circuit including a chopper, differential amplifier, and dummy core. The chopper swaps input to output connections during different states. The dummy core is coupled to a dummy chopper input. Three bond wires coupling the sensor output to a sensor chopper input, a first chopper output to a first sensor input, and a second chopper output to a second sensor input can connect the sensor and integrated circuit. The device can include a dummy pad and dummy bond wire connecting the dummy pad to the dummy chopper input. This configuration requires four bond wires connecting the sensor and integrated circuit. A neutralization core can be connected to the sensor chopper input. The chopper can change states to smear noise across a wide range, or away from a band of interest.

First claim

We claim:

1. A pseudo-differential accelerometer resistant to electromagnetic interference, the pseudo-differential accelerometer comprising:
a microelectromechanical device including a capacitive sensor core having a first sensor core input, a second sensor core input and a sensor core output;
an integrated circuit including a chopper system, a differential amplifier, a dummy core and a reference voltage, the integrated circuit being coupled to the microelectromechanical device by bond wires;
the differential amplifier including an inverting input, a non-inverting input and producing an amplifier output voltage;
the chopper system having a plurality of chopper inputs and a plurality of chopper outputs wherein during a chop state 0 the chopper system connects a first set of the plurality of chopper inputs to a first set of the plurality of chopper outputs and during a chop state 1 the chopper system connects a second set of the plurality of chopper inputs to a second set of the plurality of chopper outputs;
the dummy core being coupled to a dummy core chopper input of the chopper system;

a sensor core bond wire coupling the sensor core output of the capacitive sensor core to a sensor core chopper input of the chopper system;
a first feedback bond wire coupling a first feedback signal to the first sensor core input of the capacitive sensor core, the first feedback bond wire being coupled to a first chopper feedback output; and
a second feedback bond wire coupling a second feedback signal to the second sensor core input of the capacitive sensor core, the second feedback bond wire being coupled to a second chopper feedback output;
wherein when the chopper system is in the chop state 0 , the chopper system connects the sensor core chopper input to the inverting input of the differential amplifier, connects the dummy core chopper input to the non-inverting input of the differential amplifier, connects the first chopper feedback output to a difference of the amplifier output and reference voltages, connects the second chopper feedback output to a sum of the amplifier output and reference voltages; and
when the chopper system is in the chop state 1, the chopper system connects the sensor core chopper input to the non-inverting input of the differential amplifier, connects the dummy, core chopper input to the inverting input of the differential amplifier, connects the first chopper feedback output to the inverse of the difference of the amplifier output and reference voltages, connects the second chopper feedback output to the inverse of the sum of the amplifier output and reference voltages, the inverse of the difference of the amplifier output and reference voltages having the same magnitude and opposite polarity as the difference of the amplifier output and reference voltages, and the inverse of the sum of the amplifier output and reference voltages having the same magnitude and opposite polarity as the sum of the amplifier output and reference voltages.

2. The pseudo differential accelerometer of claim 1 , wherein the dummy core includes a first dummy core input, a second dummy core input and a dummy core output, the dummy core output being coupled to the dummy core chopper input of the chopper system;
wherein when the chopper system is in the chop state 0 , the chopper system connects the reference voltage to the first dummy core input, and connects the inverse reference voltage to the second dummy core input, the inverse reference voltage, having the same magnitude and opposite polarity as the reference voltage, and
when the chopper system is in the chop state 1, the chopper system connects the inverse reference voltage to the first dummy core input, and connects the reference voltage to the second. dummy core input.

3. The pseudo-differential accelerometer of claim 2 , wherein the dummy core includes a first dummy capacitor having a first dummy capacitor input and a first dummy capacitor output, and a second dummy capacitor having a second dummy capacitor input and a second dummy capacitor output, the first dummy capacitor input being the first dummy core input, the second dummy capacitor input being the second dummy core input, and a common node receiving the first and second dummy capacitor outputs being the dummy core output.

4. The pseudo-differential accelerometer of claim 2 , wherein the chopper system is varied between the chop state 0 and the chop state 1 at frequencies that smear noise away from a frequency band of interest.

5. The pseudo-differential accelerometer claim 2 , wherein the chopper system is varied between the chop state 0 and the chop state 1 at frequencies that smear noise substantially evenly across a wide frequency range.

6. The pseudo-differential accelerometer of claim 2 , wherein only the sensor core bond wire, and the first and second feedback bond wires are required to fully connect the capacitive sensor core of the microelectromechanical device to the integrated circuit.

7. The pseudo-differential accelerometer of claim 2 , further comprising a neutralization core connected to the sensor core chopper input of the chopper system.

8. The pseudo-differential accelerometer of claim 7 , wherein the neutralization core includes a first neutralization core input, a second neutralization core input and a neutralization core output, the neutralization core output being coupled to the sensor core chopper input of the chopper system;
wherein when the chopper system is in the chop state 0 , the chopper system connects the first neutralization core input to the inverse of the difference of the amplifier output and reference voltages, connects the second neutralization core input to the inverse of the sum of the amplifier output and reference voltages; and
when the chopper system is in the chop state 1, the chopper system connects the first neutralization core input to a difference of the amplifier output and reference voltages, connects the second neutralization core input to a sum of the amplifier output and reference voltages.

9. The pseudo-differential accelerometer of claim 8 , wherein the neutralization core includes a first neutralization capacitor having a first neutralization capacitor input and a first neutralization capacitor output, and a second neutralization capacitor having a second neutralization capacitor input and a second neutralization capacitor output, the first neutralization capacitor input being the first neutralization core input, the second neutralization capacitor input being the second neutralization core input, and a common node receiving the first and second neutralization capacitor outputs being the neutralization core output.

10. The pseudo-differential accelerometer of claim 8 , wherein only the sensor core bond wire, and the first and second feedback bond wires are required to fully connect the capacitive sensor core of the microelectromechanical device to the integrated circuit.

11. The pseudo-differential accelerometer of claim 1 , further comprising a dummy bond wire, and wherein the microelectromechanical device further includes a dummy pad, the dummy bond wire connecting the dummy pad to the dummy core chopper input.

12. The pseudo-differential accelerometer of claim 11 , wherein the dummy core includes a first dummy core input, a second dummy core input and a dummy core output, the dummy core output being coupled to the dummy core chopper input of the chopper system;
wherein When the chopper system is in the chop state 0 , the chopper system connects the reference voltage to the first dummy core input, and connects the inverse reference voltage to the second dummy core input, the inverse reference voltage having the sam

Assignees

• Bosch Gmbh Robert

Inventors

• Balachandran Ganesh
• Petkov Vladimir

Classifications

• H10W90/753

  between laterally-adjacent chips · CPC title

• H10W72/932

  Plan-view shape, i.e. in top view · CPC title

• G01D5/2417

  by varying separation · CPC title

• G01P15/0802

  Details · CPC title

• G01P15/125 Primary

  by capacitive pick-up · CPC title