Pressure sensor having sense elements in multiple wheatstone bridges with chained outputs

Patent metadata

Field	Value
Publication number	US-10260981-B2
Application number	US-201715424994-A
Country	US
Kind code	B2
Filing date	Feb 6, 2017
Priority date	Feb 6, 2017
Publication date	Apr 16, 2019
Grant date	Apr 16, 2019

Abstract

A pressure sensor includes a diaphragm suspended across a cavity in a substrate. A first group of piezoresistors is provided in the diaphragm, the piezoresistors of the first group being coupled to one another to form a first Wheatstone bridge having first positive and negative output nodes. A second group of piezoresistors is provided in the diaphragm, the piezoresistors of the second group being coupled to one another to form a second Wheatstone bridge having second positive and negative output nodes. The first negative output node of the first Wheatstone bridge is electrically connected to the second positive output node of the second Wheatstone bridge to directly chain the outputs of the Wheatstone bridges. The first and second Wheatstone bridges each produce an output signal as a function of an external pressure stimulus that is combined via the chained arrangement of the Wheatstone bridges to produce a composite output signal.

First claim

What is claimed is:

1. A pressure sensor comprising:
a substrate having a cavity;
a diaphragm suspended across said cavity;
a first group of sense elements provided in said diaphragm, said sense elements of said first group being coupled to one another to form a first Wheatstone bridge, said first Wheatstone bridge having a first positive output node and a first negative output node; and
a second group of sense elements provided in said diaphragm, said sense elements of said second group being coupled to one another to form a second Wheatstone bridge, said second Wheatstone bridge having a second positive output node and a second negative output node, wherein said first negative output node of said first Wheatstone bridge is electrically connected to said second positive output node of said second Wheatstone bridge, said first positive output node of said first Wheatstone bridge is electrically disconnected from said second negative output node of said second Wheatstone bridge, and said first and second Wheatstone bridges produce a composite output signal as a function of an external pressure stimulus detected by said each of said first and second Wheatstone bridges.

2. The pressure sensor of claim 1 wherein:
said first Wheatstone bridge has a first positive input node and a first negative input node;
said second Wheatstone bridge has a second positive input node and a second negative input node; and
said pressure sensor further comprises a current source interconnected between said first positive input node and said first negative input node of said first Wheatstone bridge, said current source further being interconnected between said second positive input node and said second negative input node of said second Wheatstone bridge, and said current source being configured to deliver a supply current to said each of said first and second Wheatstone bridges.

3. The pressure sensor of claim 2 wherein one of said first and second negative input nodes is electrically coupled to a system ground and the other of said first and second negative input nodes is not electrically coupled to said system ground.

4. The pressure sensor of claim 1 further comprising a differential amplifier having a positive terminal, a negative terminal, and an output terminal wherein said first positive output node of said first Wheatstone bridge is electrically connected to said positive terminal, said second negative output node of said second Wheatstone bridge is in electrical communication with said negative terminal, and said output terminal provides said composite output signal.

5. The pressure sensor of claim 1 further comprising additional groups of sense elements provided in said diaphragm to form additional Wheatstone bridges, each of said additional Wheatstone bridges having a positive output node and a negative output node, wherein said second negative output node of said second Wheatstone bridge is electrically connected to said positive output node of a first one of said additional Wheatstone bridges, and said negative output node of each of said additional Wheatstone bridges is electrically connected to said positive output node of a successive one of said additional Wheatstone bridges to form a chained arrangement of said first, second, and additional Wheatstone bridges to produce said composite output signal.

6. The pressure sensor of claim 5 further comprising a current source interconnected between a positive input node and a negative input node of each of said first Wheatstone bridge, said second Wheatstone bridge, and said each of said additional Wheatstone bridges, said current source being configured to deliver a supply current to each of said Wheatstone bridges.

7. The pressure sensor of claim 5 further comprising a differential amplifier having a positive terminal, a negative terminal, and an output terminal wherein said first positive output node of said first Wheatstone bridge is electrically connected to said positive terminal, said negative output node of a last one of said additional Wheatstone bridges in said chain is electrically connected to said negative terminal, and said output terminal provides said composite output signal.

8. The pressure sensor of claim 1 wherein said diaphragm includes regions that are under high stress relative to other regions of said diaphragm, and said sense elements of each of said first and second groups of sense elements are located within said regions that are under high stress.

9. The pressure sensor of claim 1 wherein said diaphragm has first and second outer edges, said first group of sense elements forming said first Wheatstone bridge is located proximate said first outer edge, and said second group of sense elements forming said second Wheatstone bridge is located proximate said second outer edge.

10. The pressure sensor of claim 1 wherein said diaphragm includes a central region circumscribed by outer edges, said first group of sense elements forming said first Wheatstone bridge is located proximate one of said first outer edges, and said second group of sense elements forming said second Wheatstone bridge is located at said central region.

11. The pressure sensor of claim 1 wherein said diaphragm has an outer edge, said first group of sense elements forming said first Wheatstone bridge is located proximate said outer edge, and said second group of sense elements forming said second Wheatstone bridge is located proximate said outer edge and adjacent to said first group of sense elements.

12. The pressure sensor of claim 1 wherein:
said diaphragm has first, second, third, and fourth outer edges, said first and second outer edges being disposed on opposing sides of a surface of said diaphragm, and said third and fourth outer edges being disposed on opposing sides of said surface of said diaphragm and interposed between said first and second outer edges so that said surface of said diaphragm is circumscribed by said first, second, third, and fourth outer edges;
one each of said sense elements of said first group of sense elements forming said first Wheatstone bridge is located proximate one each of said first, second, third, and fourth edges; and
one each of said sense elements of said second group of sense elements forming said second Wheatstone bridge is located proximate said one each of said first, second, third, and fourth edges.

13. The pressure sensor of claim 1 wherein:
said diaphragm includes a central region circumscribed by first, second, third, and fourth outer edges;
one each of said sense elements of said first group of sense elements forming said first Wheatstone bridge is located proximate one each of said first, second, third, and fourth edges; and
said second group of sense elements forming said second Wheatstone bridge is located at said central region.

14. A pressure sensor comprising:
a substrate having a cavity;
a diaphragm suspended across said cavity, said diaphragm including regions that are under high stress relative to other regions of said diaphragm; and
a plurality of groups of sense elements provided in said diaphragm within said regions that are under high stress, said groups of sense elements forming a plurality of Wheatstone bridges, each of said plurality of Wheatstone bridges having a positive output node and a negative output node, wherein for said plurality of Wheatstone bridges, said negative output node of an immediately preceding one of said Wheatstone bridges is electrically connected to said positive output node of an immediately successive one of said Wheatstone bridges to form a chained arrangement of said plurality of Wheatstone bridges, said

Assignees

• Nxp Usa Inc

Inventors

• Holm Paige M
• Schlarmann Mark Edward

Classifications

• G01L9/06

  of piezo-resistive devices · CPC title

• G01L9/0052 Primary

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

• G01L19/148 Primary

  Details about the circuit board integration, e.g. integrated with the diaphragm surface or encapsulation · CPC title

• G01L1/18 Primary

  using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material · CPC title

• G01L9/0054

  integral with a semiconducting diaphragm · CPC title