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US 8,427,075 B2Granted
Constant current output sink or source
AssigneeMicrochip Technology Incorporated
InventorsWard R. Brown, Randy Yach
Life of this patent
Estimating the term…
Abstract
A constant current output sink or source eliminates a current limiting series resistor for a light emitting diode (LED) and maintains a constant light intensity from the LED for all operating and manufacturing variables of a digital device since the current through the LED is maintained at a constant value. The constant current output sink or source may be programmable for selection of a constant current value from a plurality of constant current values available.
Claims26
An integrated circuit digital device, comprising:
- an input/output driver circuit driving an input/output connection of the integrated circuit digital device, wherein the input/output driver circuit is selectable to operate as a digital input/output driver or as a current limited output driver;
- and
- a programmable constant current circuit which is configured to be coupled to the input/output connection when the input/output driver is configured to operate as a current limited output driver, wherein the programmable constant current circuit limits the amount of current through the input/output connection to a current value that is programmed into the programmable constant current circuit.
An integrated circuit digital device having an output node that is current limited, comprising:
- an output node;
- a high side drive circuit coupled between the output node and a power supply voltage;
- a first multiplexer having first, second and third nodes, and a control input for selectively coupling the first node to the second node or the first node to the third node, wherein the first node is coupled to the output node and the high side drive circuit;
- a second multiplexer having first, second and third nodes, and a control input for selectively coupling the first node to the second node or the first node to the third node, wherein the first node is coupled to a power supply common;
- a programmable constant current circuit coupled between the second node of the first multiplexer and the second node of the second multiplexer, wherein the programmable constant current circuit limits current therethrough to a current value that is programmed into the programmable constant current circuit;
- and
- a low side drive circuit coupled between the third nodes of the first and second multiplexers;
- wherein when the first and second nodes of the first and second multiplexers are coupled together the programmable constant current circuit limits current going into the output node to the current value, and when the first and third nodes of the first and second multiplexers are coupled together the low side drive circuit couples the output node to substantially the power supply common without limiting current thereto.
5 more elements
An integrated circuit digital device having an output node that is current limited, comprising:
- an output node;
- a low side drive circuit coupled between the output node and a power supply common;
- a first multiplexer having first, second and third nodes, and a control input for selectively coupling the first node to the second node or the first node to the third node, wherein the first node is coupled to a power supply voltage;
- a second multiplexer having first, second and third nodes, and a control input for selectively coupling the first node to the second node or the first node to the third node, wherein the first node is coupled to the output node and the low side drive circuit;
- a programmable constant current circuit coupled between the second node of the first multiplexer and the second node of the second multiplexer, wherein the programmable constant current circuit limits current therethrough to a current value that is programmed into the programmable constant current circuit;
- and
- a high side drive circuit coupled between the third nodes of the first and second multiplexers;
- wherein when the first and second nodes of the first and second multiplexers are coupled together the programmable constant current circuit limits current going from the output node to the current value, and when the first and third nodes of the first and second multiplexers are coupled together the high side drive circuit couples the output node to substantially the power supply voltage without limiting current thereto.
5 more elements
Dependencies are inferred from the claim text.