Current sensing circuit
First Claim
1. A current sensing circuit coupled between a load having a load current passing therethrough and a supply voltage terminal, comprising:
- a first current means coupled between said load and said supply voltage terminal for carrying a first portion of said load current;
resistive means coupled to said supply voltage terminal for providing a voltage drop;
second current means coupled between said load and said resistive means for carrying a second portion of said load current, said first portion being substantially larger than said second portion;
control means coupled to said first current means and said second current means for biasing said first current means and said second current means;
output means coupled to a first node between said second current means and said resistive means for providing an output.
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Accused Products
Abstract
A current sensing circuit is disclosed wherein a small portion of a load current is sampled through a sensing resistor and a substantially larger portion of the load current is allowed to bypass the sensing resistor. A first high current vertical MOS transistor is coupled between the load and the ground terminal. A second vertical MOS transistor is coupled in series between the load and ground terminal. The transistors are constructed in a vertical MOS cellular construction whereby the first transistor comprises on the order of three-thousand cells and the second transistor comprises a single cell. A signal is taken across the sensing resistor and may be provided as feedback to a control means driving the first and second transistors for performing a current limiting or constant current function.
113 Citations
8 Claims
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1. A current sensing circuit coupled between a load having a load current passing therethrough and a supply voltage terminal, comprising:
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a first current means coupled between said load and said supply voltage terminal for carrying a first portion of said load current; resistive means coupled to said supply voltage terminal for providing a voltage drop; second current means coupled between said load and said resistive means for carrying a second portion of said load current, said first portion being substantially larger than said second portion; control means coupled to said first current means and said second current means for biasing said first current means and said second current means; output means coupled to a first node between said second current means and said resistive means for providing an output. - View Dependent Claims (2, 3, 4)
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5. A current sensing circuit having an input terminal for receiving a load current, a supply voltage terminal and an output terminal, comprising:
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a first transistor having current carrying electrodes coupled between said input terminal and said supply voltage terminal; a second transistor having a first current carrying electrode coupled to said input terminal; resistive means coupled between a second current carrying electrode of said second transistor and said supply voltage terminal for providing a voltage drop, wherein said second current carrying electrode is also coupled to said output terminal; and a drive circuit coupled to a control electrode of each of said first and second transistors. - View Dependent Claims (6, 7)
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8. A circuit for providing a constant current to a load comprising:
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first current means coupled between said load and a supply voltage terminal for carrying a first portion of said current; resistive means coupled to said supply voltage terminal for providing a voltage drop; second current means coupled between said load and said resistive means for carrying a second portion of said current, said first portion being substantially larger than said second portion; control means coupled to said first and second current means for controlling the value of said first portion and said second portion; and drive means coupled from a node between said resistive means and said second current means to said control means and for driving said control means.
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Specification