Pressure sensor device for measuring a differential normal pressure to the device and related methods

Patent metadata

Field	Value
Publication number	US-9719874-B2
Application number	US-201514754788-A
Country	US
Kind code	B2
Filing date	Jun 30, 2015
Priority date	Jun 30, 2015
Publication date	Aug 1, 2017
Grant date	Aug 1, 2017

Abstract

A pressure sensor device is to be positioned within a material where a mechanical parameter is measured. The pressure sensor device may include an IC having a ring oscillator with an inverter stage having first doped and second doped piezoresistor couples. Each piezoresistor couple may include two piezoresistors arranged orthogonal to one another with a same resistance value. Each piezoresistor couple may have first and second resistance values responsive to pressure. The IC may include an output interface coupled to the ring oscillator and configured to generate a pressure output signal based upon the first and second resistance values and indicative of pressure normal to the IC.

First claim

That which is claimed is:

1. A pressure sensor device to be positioned within a material where a mechanical parameter is measured, the pressure sensor device comprising:
an integrated circuit (IC) comprising
a ring oscillator comprising at least one inverter stage comprising first doped and second doped piezoresistor couples,
each piezoresistor couple comprising two piezoresistors arranged orthogonal to one another with a same resistance value,
each piezoresistor couple having first and second resistance values responsive to pressure, and
an output interface coupled to said ring oscillator and configured to generate a pressure output signal based upon the first and second resistance values and indicative of pressure normal to said IC.

2. The pressure sensor device of claim 1 wherein said first doped piezoresistor couple comprises a semiconductor material having a first conductivity type; and wherein said second doped piezoresistor couple comprises semiconductor material having a second conductivity type.

3. The pressure sensor device of claim 1 wherein said output interface comprises a wireless transmitter.

4. The pressure sensor device of claim 3 wherein the output interface comprises a modulator coupled upstream of said wireless transmitter and configured to generate the pressure output signal by modulating an output of said ring oscillator circuit.

5. The pressure sensor device of claim 4 wherein said modulator is configured to operate based upon an amplitude-shift keying modulation.

6. The pressure sensor device of claim 1 wherein said at least one inverter stage comprises a capacitor coupled to said first and second doped piezoresistor couples.

7. A method of determining a pressure, the method comprising:
experiencing a pressure at a pressure sensor, the pressure experienced in first, second and third directions that are orthogonal to one another;
using a first n-doped piezoresistor and a first p-doped piezoresistor to cancel out a pressure effect in the first direction, the first n-doped piezoresistor and the first p-doped piezoresistor being arranged in a first common orientation;
using a second n-doped piezoresistor and a second p-doped piezoresistor to cancel out a pressure effect in the second direction, the second n-doped piezoresistor and the second p-doped piezoresistor being arranged in a second common orientation that is orthogonal with the first common orientation; and
determining a pressure measurement indicative of a pressure experienced in the third direction, the third direction being normal to a horizontal plane of the pressure sensor.

8. The method of claim 7 , wherein determining the pressure measurement comprises using ring oscillator circuitry that comprises a first inverter coupled to the first n-doped piezoresistor and the second n-doped piezoresistor and a second inverter coupled to the first p-doped piezoresistor and the second p-doped piezoresistor, wherein the first and second inverters are different inverters or the same inverter.

9. The method of claim 8 , wherein the ring oscillator circuitry comprises a first ring oscillator that comprises the first inverter and a second ring oscillator that comprises the second inverter.

10. The method of claim 7 , wherein the pressure sensor is embedded in a solid material, the method further comprising wirelessly transmitting a pressure output signal that provides an indication of the pressure measurement.

11. The method of claim 10 , further comprising calibrating the pressure sensor with a known amount of pressure normal to the horizontal plane of the pressure sensor to determine a piezoresistivity of each of the first n-doped piezoresistor, the second n-doped piezoresistor, the first p-doped piezoresistor and the second p-doped piezoresistor.

12. A pressure sensor to be positioned within a material to measure pressure in the material, the pressure sensor comprising:
ring oscillator circuitry comprising:
a first inverter coupled to a first piezoresistor couple, the first piezoresistor couple including a first n-doped piezoresistor and a second n-doped piezoresistor that are arranged orthogonal to one another across a surface of the pressure sensor, the first n-doped piezoresistor and a second n-doped piezoresistor having the same resistance value; and
a second inverter coupled to a second piezoresistor couple, the second piezoresistor couple including a first p-doped piezoresistor and a second p-doped piezoresistor that are arranged orthogonal to one another across the surface of the pressure sensor, the first p-doped piezoresistor and a second p-doped piezoresistor having the same resistance value;
wherein the first and second inverters are different inverters or the same inverter and wherein each piezoresistor couple has a resistance value responsive to pressure; and

an output interface coupled to the ring oscillator circuitry configured to generate a pressure output signal based upon the resistance values in the ring oscillator circuitry, and indicative of pressure normal to the pressure sensor.

13. The pressure sensor of claim 12 , wherein the first inverter and the second inverter are different inverters, the first and second n-doped piezoresistors being coupled to an output of the first inverter and the first and second p-doped piezoresistors being coupled to the output of the second inverter.

14. The pressure sensor of claim 12 , wherein the first inverter and the second inverter are a single inverter, the first and second n-doped piezoresistors and the first and second p-doped piezoresistors being coupled to the output of the single inverter.

15. The pressure sensor of claim 14 , further comprising:
a first transistor coupled between the output of the single inverter and the first and second n-doped piezoresistors; and
a second transistor coupled between the output of the single resistor and the first and second p-doped piezoresistors.

16. The pressure sensor of claim 14 , further comprising:
a first diode coupled between the output of the single inverter and the first and second n-doped piezoresistors; and
a second diode coupled between the output of the single resistor and the first and second p-doped piezoresistors.

17. The pressure sensor of claim 12 , wherein the first and second inverters are two separate inverters;
wherein the first inverter comprises a first p-channel transistor coupled in series with a first n-channel transistor between a reference voltage node and a ground node, the first and second n-doped piezoresistors coupled between the first p-channel transistor and the reference voltage node;
wherein the pressure sensor further comprises third and fourth n-doped piezoresistors coupled between the first n-channel transistor and the ground node, the third n-doped piezoresistor being arranged in the same direction as the first n-doped piezoresistor and the fourth n-doped piezoresistor being arranged in the same direction as the second n-doped piezoresistor;
wherein the second inverter comprises a second p-channel transistor coupled in series with a second n-channel transistor between the reference voltage node and the ground node, the first and second p-doped piezoresistors coupled between the second p-channel transistor and the reference voltage node; and
wherein the pressure sensor further comprises third and fourth p-doped piezoresistors coupled between the second n-channel transistor and the ground node, the third p-doped piezoresistor being arranged in the same direction as the first p-doped piezoresistor and the fourth p-doped piezoresistor being arrange

Assignees

• St Microelectronics Srl

Inventors

• Motta Alessandro
• Pagani Alberto
• Sicurella Giovanni

Classifications

• G01L9/065

  with temperature compensating means (non electric temperature compensating means G01L19/04) · CPC title

• G01L9/0052 Primary

  of piezoresistive elements (circuits therefor G01L9/06) · CPC title

• G01L9/04

  of resistance-strain gauges · CPC title

• G01L1/225 Primary

  Measuring circuits therefor · CPC title