Bidirectional current blocking MOSFET for battery disconnect switching including protection against reverse connected battery charger
AssigneeSiliconix Incorporated
InventorRichard K. Williams
Life of this patent
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Abstract
A bidirectional current blocking switch is disclosed. The switch includes a four-terminal MOSFET in which there is no source-body short. The voltages applied to the source and drain terminals are both higher than the voltage applied to the body terminal (for an N-channel) device so that the source-body and drain-body junction of the MOSFET never become forward-biased. The switch of this invention is particularly useful for switching a cascaded set of batteries in a portable computer. Also included is a disclosure of circuitry to protect the switch against a reverse connected battery charger.
Claims16
A bidirectional current blocking switch comprising:
- a first MOSFET comprising:
- a semiconductor substrate;
- a first N region and a second N region formed in said substrate and being connected to first and second terminals, respectively;
- a P body region formed in said substrate, said P body region comprising a channel region located between said first and second N regions, said P body region being connected to ground;
- and
- a gate;
- wherein neither of said first and second N regions is permanently shorted to said P body region;
- second and third MOSFETs connected in series between said gate and said second terminal of said first MOSFETs;
- and
- a fourth MOSFET connected between said P body region and said second terminal of said first MOSFET, a gate of said fourth MOSFET being connected to said first terminal of said first MOSFET.
A bidirectional current blocking switch comprising:
- a first MOSFET comprising:
- a semiconductor substrate;
- a first N region and a second N region formed in said substrate and being connected to first and second terminals, respectively;
- a P body region formed in said substrate, said P body region comprising a channel region located between said first and second N regions, said P body region being connected to ground;
- and
- a gate;
- wherein neither of said first and second N regions is permanently shorted to said P body region;
- a second MOSFET, said second MOSFET not including a source-body short, a body region of said second MOSFET being connected to ground, said second MOSFET being connected between said gate and said second terminal of said first MOSFET;
- and
- a third MOSFET connected between said P body region and said second terminal of said first MOSFET, a gate of said third MOSFET being connected to said first terminal of said first MOSFET.
A bidirectional current blocking switch in the form of an integrated circuit comprising:
- a P substrate;
- a first N region and a second N region, said first N region and said second N region being separated by a first region of said P substrate, a first gate overlying said first region of said P substrate;
- a third N region, said third N region being separated from said second N region by a second region of said P substrate, a second gate overlying said second region of said P substrate;
- said second gate being connected to said P substrate;
- a first terminal connected to said first N region;
- a second terminal connected to said second N region;
- and
- a third terminal connected to said first gate and to said third N region;
- wherein none of said N regions is shorted to said P substrate.
A bidirectional current blocking switch comprising a first MOSFET, said first MOSFET not including a permanent source-body short, and a pair of MOSFETs connected in series between a gate and a first terminal of said first MOSFET, said bidirectional current blocking switch further comprising a fourth MOSFET connected between said first terminal and a body region of said first MOSFET.
A bidirectional current blocking switch comprising a first MOSFET and a second MOSFET, neither of said first or second MOSFETs including a permanent source-body short, said second MOSFET being connected between a gate and a first terminal of said first MOSFET, a body of said first MOSFET and a body and a gate of said second MOSFET being connected together.
Dependencies are inferred from the claim text.