US 2018/0019740 A1Published application

Method and apparatus for protecting gate-source junction of low-voltage mosfet in high-voltage circuit

AssigneeNuvoton Technology Corporation

InventorJan-Harm Nieland

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Abstract

A high-voltage circuit has a protection circuit protecting a low-voltage MOSFET. A first MOSFET, a low-voltage device with a gate coupled to an input voltage, is coupled in a series with a second MOSFET which is a high-voltage device, both of a first conductivity type. A protection circuit includes a third, a fourth, and a fifth MOSFET. The third MOSFET has a second conductivity type and source and body coupled to the input voltage. The fourth MOSFET has the first conductivity type and a drain coupled to a drain of the third MOSFET, a gate coupled to a second bias voltage, and a source and a body coupled to the first power terminal. The fifth MOSFET has the first conductivity type and a drain coupled to the input voltage, a gate coupled to the drain of the fourth MOSFET, and a source coupled to the first power terminal.

Claims20

Dependent claims

A high-voltage circuit including a protection circuit for protecting a low-voltage MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), wherein high-voltage devices are configured to operate with a power supply voltage and low-voltage devices are configured to operate with a maximum allowable voltage lower than the power supply voltage, the high-voltage circuit comprising:

a first MOSFET, being a low-voltage device of a first conductivity type and having a gate coupled to an input voltage and a source coupled to a first power terminal;
a second MOSFET, being a high-voltage device of the first conductivity type and in a series connection with the first MOSFET, the second MOSFET having a source coupled to a drain of the first MOSFET and a gate coupled to a first bias voltage;
and
a protection circuit for protecting the gate-source junction of the first MOSFET, the protection circuit including:
a third MOSFET, being a device of a second conductivity type and having a source to the input voltage;
a fourth MOSFET, being a device of the first conductivity type and having a drain coupled to a drain of the third MOSFET, a gate coupled to a second bias voltage, and a source and a body coupled to the first power terminal;
and
a fifth MOSFET, being a device of the first conductivity type and having a drain coupled to the input voltage, a gate coupled to the drain of the fourth MOSFET, and a source coupled to the first power terminal.

5 more elements

A high-voltage circuit including a protection circuit for protecting a low-voltage MOSFET device, wherein high-voltage devices are configured to operate with a power supply voltage and low-voltage devices are configured to operate with a maximum allowable voltage lower than the power supply voltage, the high-voltage circuit comprising:

a first MOSFET, being a low-voltage NMOS device and having a gate coupled to an input voltage and a source coupled to a ground;
a second MOSFET, being a high-voltage NMOS device and in a series connection with the first MOSFET, the second MOSFET having a source coupled to a drain of the first MOSFET and a gate coupled to a first bias voltage;
and
a protection circuit for protecting the gate-source junction of the first MOSFET, the protection circuit including:
a third MOSFET, being a PMOS device and having a source and a body coupled to the input voltage, and a gate coupled to the first bias voltage;
a fourth MOSFET, being a NMOS device and having a drain coupled to a drain of the third MOSFET, a gate coupled to a second bias voltage, and a source and a body coupled to the ground;
and
a fifth MOSFET, being a NMOS device and having a drain coupled to the input voltage, a gate coupled to the drain of the fourth MOSFET, and a source coupled to the ground.

5 more elements

A high-voltage circuit including a protection circuit for protecting a low-voltage MOSFET device, wherein high-voltage devices are configured to operate with a power supply voltage and low-voltage devices are configured operate with a maximum allowable voltage lower than the power supply voltage, the high-voltage circuit comprising:

a first MOSFET, being a low-voltage PMOS device and having a gate coupled to an input voltage and a source coupled to a power supply;
a second MOSFET, being a high-voltage PMOS device and in a series connection with the first MOSFET, the second MOSFET having a source coupled to a drain of the first MOSFET and a gate coupled to a first bias voltage;
and
a protection circuit for protecting the gate-source junction of the first MOSFET, the protection circuit including:
a third MOSFET, being an NMOS device and having a source coupled to the input voltage and a gate coupled to the first bias voltage;
a fourth MOSFET, being a PMOS device and having a drain coupled to a drain of the third MOSFET, a gate coupled to a second bias voltage, and a source and a body coupled to a power supply terminal;
and
a fifth MOSFET, being a PMOS device of the first conductivity type and having a drain coupled to the input voltage, a gate coupled to the drain of the fourth MOSFET, and a source coupled to the power supply terminal.

5 more elements

Dependencies are inferred from the claim text.