Low voltage isolation switch, in particular for a transmission channel for ultrasound applications

A switching circuit, comprising:

• a connection terminal;
• an output terminal;
• first and second voltage reference terminals;
• first and second switching transistors electrically coupled in series to each other, and having respective body diodes coupled in anti-series, between said connection terminal and said output terminal, the first switching transistor having a first control terminal and the second switching transistor having a second control terminal;
• a bootstrap circuit connected to the first and second control terminals and to the first and second voltage references and including:
• first and second bootstrap nodes;
• a first parasitic capacitance electrically coupled between said first control terminal and the first bootstrap node;
• and
• a second parasitic capacitance electrically coupled between said second control terminal and the second bootstrap node, the first and second parasitic capacitances having capacitance values of at least one order of magnitude lower than gate-source capacitances of said first and second switching transistors, wherein said bootstrap circuit further comprises:
• a first bootstrap transistor and a first bootstrap resistive element electrically coupled in series to each other between said first control terminal and said second bootstrap node;
• and
• a second bootstrap transistor and a second bootstrap resistive element electrically coupled in series to each other between said second control terminal and said first bootstrap node.

A transmission channel comprising:

• a connection terminal;
• an output terminal;
• and
• a switching circuit having:
• first and second voltage reference terminals;
• first and second switching transistors electrically coupled in series to each other, and having respective body diodes coupled in anti-series, between said connection terminal and said output terminal, the first switching transistor having a first control gate and the second switching transistor having a second control gate;
• a bootstrap circuit connected to the first and second control gates and to the first and second voltage references and including:
• first and second bootstrap nodes;
• a first parasitic capacitance electrically coupled directly between said first control gate and the first bootstrap node;
• and
• a second parasitic capacitance electrically coupled directly between said second control gate and the second bootstrap node, the first and second parasitic capacitances having capacitance values of at least one order of magnitude lower than gate-source capacitances of said first and second switching transistors.

A transmission channel comprising:

• a connection terminal;
• an output terminal;
• and
• a switching circuit having;
• first and second voltage reference terminals;
• first and second switching transistors electrically coupled in series to each other, and having respective body diodes coupled in anti-series, between said connection terminal and said output terminal, the first switching transistor having a first control gate and the second switching transistor having a second control gate;
• a bootstrap circuit connected to the first and second control gates and to the first and second voltage references and including:
• first and second bootstrap nodes;
• a first parasitic capacitance electrically coupled between said first control gate the first bootstrap node;
• and
• a second parasitic capacitance electrically coupled between said second control gate and the second bootstrap node, the first and second parasitic capacitances having capacitance values of at least one order of magnitude lower than gate-source capacitances of said first and second switching transistors, wherein said bootstrap circuit further comprises:
• a first bootstrap transistor and a first bootstrap resistive element electrically coupled in series to each other between said first control gate and said second bootstrap node;
• and
• a second bootstrap transistor and a second bootstrap resistive element electrically coupled in series to each other between said second control gate and said first bootstrap node.

A method, comprising:

• transmitting a high voltage signal from a high voltage input terminal to an input/output terminal while a switching circuit, electrically coupled between the input/output terminal and a low voltage output terminal, blocks the high voltage signal from the low voltage output terminal;
• and
• receiving a low voltage signal at the input/output terminal;
• and
• transmitting the low voltage signal through the switching circuit to said low voltage output terminal, wherein the switching circuit includes:
• first and second voltage reference terminals;
• first and second switching transistors electrically coupled in series to each other, and having respective body diodes coupled in anti-series between said input/output terminal and said low voltage output terminal, the first switching transistor having a first control gate and the second switching transistor having a second control gate;
• a bootstrap circuit connected to the first and second control gates and to the first and second voltage references and including:
• first and second bootstrap nodes;
• a first parasitic capacitance electrically coupled directly between said first control gate and the first bootstrap node;
• and
• a second parasitic capacitance electrically coupled directly between said second control gate and the second bootstrap node, the first and second parasitic capacitances having capacitance values of at least one order of magnitude lower than gate-source capacitances of said first and second switching transistors.