High voltage analog switch

Patent metadata

Field	Value
Publication number	US-9401659-B2
Application number	US-201414563675-A
Country	US
Kind code	B2
Filing date	Dec 8, 2014
Priority date	Nov 12, 2014
Publication date	Jul 26, 2016
Grant date	Jul 26, 2016

Abstract

A high voltage analog switch can be used in medical ultrasound applications. The high voltage analog switch can pass high voltage transducer excitation signals without necessarily having any high voltage power supplies. The high voltage analog switch can include three output switches, with one of the output switches having a clamp circuit for ensuring that transistors of an output switch on an input end of the high voltage analog switch remain OFF when the high voltage analog switch is OFF.

First claim

What is claimed is:

1. A high voltage analog switch comprising:
a first output switch comprising a first node coupled to a first end node of the high voltage analog switch and a second node coupled to a first node of a second output switch, the first end node of the high voltage analog switch being coupled to receive a high voltage transducer excitation signal, the first output switch including a clamp circuit that keeps the first output switch open when the high voltage analog switch is OFF;
the second output switch comprising a second node coupled to a second end node of the high voltage analog switch, the second end node of the high voltage analog switch being coupled to a piezoelectric transducer; and
a third output switch comprising a first node coupled to the second node of the first output switch and the first node of the second output switch, the third output switch comprising a second node coupled to ground,
wherein the first and second output switches are closed and the third output switch is open to pass the high voltage transducer excitation signal from the first end node to the second end node of the high voltage analog switch when the high voltage analog switch is ON, and the first and second output switches are open and the third output switch is closed when the high voltage analog switch is OFF,
wherein the first output switch comprises a first transistor and a second transistor forming an analog switch, and
the clamp circuit comprises a third transistor having a first terminal, a second terminal, and a gate, the first terminal of the third transistor being coupled to a gate of the first transistor and a gate of the second transistor, the second terminal of the third transistor being coupled to a source of the first transistor and a source of the second transistor, and the third transistor is ON to shunt the gates and the sources of the first and second transistors together when the first output switch is open.

2. The high voltage analog switch of claim 1 , wherein a source of the third transistor is coupled to the sources of the first and second transistors and a drain of the third transistor is coupled to the gates of the first and second transistors.

3. The high voltage analog switch of claim 1 , wherein the clamp circuit further comprises a clamp gate driver circuit that drives the gate of the third transistor, the clamp gate driver circuit comprising a latched cell.

4. The high voltage analog switch of claim 3 , wherein the latched cell comprises a first inverter and a second inverter, an output of the first inverter drives an input of the second inverter, an output of the second inverter drives an input of the first inverter, and the output of the second inverter drives the gate of the third transistor.

5. The high voltage analog switch of claim 4 , wherein the first inverter comprises a fourth transistor and a fifth transistor and the second inverter comprises a sixth transistor and a seventh transistor, a source of the fifth transistor and a source of the seventh transistor being coupled to the sources of the first and second transistors and a drain of the sixth transistor and a drain of the seventh transistor being coupled to the gate of the third transistor.

6. The high voltage analog switch of claim 5 , further comprising a current source and a capacitor, wherein current from the current source charges the capacitor to generate an internal supply voltage that is referenced to the sources of the first and second transistors.

7. A medical ultrasound device comprising:
a high voltage analog switch comprising a first end node and a second end node, the high voltage analog switch comprising a first output switch, a second output switch, and a third output switch, a first terminal of the first output switch being coupled to the first end node of the high voltage analog switch, a second terminal of the second output switch being coupled to the second end node of the high voltage analog switch, a first terminal of the third output switch being coupled to a second terminal of the first output switch and to a first terminal of the second output switch, a second terminal of the third output switch being coupled to ground, the high voltage analog switch further comprising a clamp circuit that keeps the first output switch open when the high voltage analog switch is OFF;
a transmitter/receiver pair being coupled to the first end node of the high voltage analog switch; and
a piezoelectric transducer coupled to the second end node of the high voltage analog switch to receive a high voltage transducer excitation signal transmitted by a transmitter of the transmitter/receiver pair through the high voltage analog switch when the high voltage analog switch is ON,
wherein the first and second output switches are closed and the third output switch is open to pass the high voltage transducer excitation signal from the first end node to the second end node of the high voltage analog switch when the high voltage analog switch is ON, and the first and second output switches are open and the third output switch is closed when the high voltage analog switch is OFF,
wherein the clamp circuit comprises a third transistor having a first terminal, a second terminal, and a gate, the first terminal of the third transistor being coupled to a gate of the first transistor and a gate of the second transistor, the second terminal of the third transistor being coupled to a source of the first transistor and a source of the second transistor, and the third transistor is ON to shunt the gates and the sources of the first and second transistors together when the first output switch is open.

8. The medical ultrasound device of claim 7 , wherein the high voltage analog switch does not have a power supply that provides more than +/−10V.

9. The medical ultrasound device of claim 7 , wherein the high voltage transducer excitation signal has a voltage of at least 80V peak-to-peak.

10. The medical ultrasound device of claim 7 , wherein the first output switch comprises a first transistor and a second transistor.

11. The medical ultrasound device of claim 7 , wherein a source of the third transistor is coupled to the sources of the first and second transistors and a drain of the third transistor is coupled to the gates of the first and second transistors.

12. The medical ultrasound device of claim 7 , wherein the clamp circuit further comprises a clamp gate driver circuit that drives the gate of the third transistor, the clamp gate driver circuit comprising a latched cell.

13. The medical ultrasound device of claim 12 , wherein the latched cell comprises a first inverter and a second inverter, an output of the first inverter drives an input of the second inverter, an output of the second inverter drives an input of the first inverter, and the output of the second inverter drives the gate of the third transistor.

14. A high voltage analog switch comprising:
a first output switch comprising a first node coupled to a transmitter/receiver pair, the first output switch comprising a first transistor and a second transistor forming a first analog switch, the first output switch further comprising a clamp circuit that keeps the first transistor and the second transistor OFF when the high voltage analog switch is OFF;
a second output switch comprising a first node coupled to a second node of the first output switch and a second node coupled to a piezoelectric transducer, the second output switch comprising a fourth transistor and a fifth transistor forming a second analog switch; and
a third output switch comprising a first node coupled to the second node of the first out

Assignees

• Lei Jimes
• Tiew Kee Chee
• Monolithic Power Systems Inc

Inventors

• Lei Jimes
• Tiew Kee Chee

Classifications

• G01S7/52017 Primary

  particularly adapted to short-range imaging (G01S7/53 takes precedence) · CPC title

• H02M7/217 Primary

  using semiconductor devices only · CPC title

• A61B8/54

  Control of the diagnostic device · CPC title

• A61B8/4405

  Device being mounted on a trolley · CPC title

• A61B8/4427

  Device being portable or laptop-like · CPC title