Level shifter and method of calibration
AssigneeTexas Instruments Incorporated
InventorNathan Richard Schemm
Life of this patent
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Abstract
A level shifter includes a signal generator that generates differential signals on a first output and a second output. A first capacitor is coupled between the first output and a first node and a second capacitor is coupled between the second output and a second node. A third capacitor is coupled between the first node and a first voltage potential, wherein the capacitance of the third capacitor is variable. A fourth capacitor is coupled between the second node and the first voltage potential, wherein the capacitance of the fourth capacitor is variable.
Claims20
A circuit comprising:
- a signal transmitter having a first transmitter terminal and a second transmitter terminal;
- a signal receiver having a first receiver terminal and a second receiver terminal;
- a first capacitor coupled between the first transmitter terminal and the first receiver terminal, and having a first capacitance;
- a second capacitor coupled between the second transmitter terminal and the second receiver terminal, and having a second capacitance;
- a third capacitor coupled between the first receiver terminal and a terminal voltage source, and having a third capacitance defining a first ratio over the first capacitance;
- and
- a fourth capacitor coupled between the second receiver terminal and the terminal voltage source, and having a fourth capacitance defining a second ratio over the second capacitance, the second ratio matching the first ratio.
A method of calibrating a level shifter, the method comprising:
- coupling a first node to a first voltage potential, the first node being coupled to a first capacitor coupled to a signal generator, a second capacitor coupled to a second voltage potential, and a first input to a first differential amplifier;
- coupling a second node to the first voltage potential, the second node being coupled to a third capacitor coupled to the signal generator, a fourth capacitor coupled to the second voltage potential, and a second input to the first differential amplifier;
- decoupling the first voltage from the first node and the second node;
- sweeping a voltage across the level shifter to generate a differential voltage between the first node and the second node;
- measuring the voltage difference between the first node and the second node;
- and
- adjusting the capacitance value of at least one of the second capacitor and the fourth capacitor in response to the measuring.
A method comprising:
- generating, by a transmitter, a first signal having a first voltage amplitude during a calibration mode;
- generating, by the transmitter, a second signal having a second voltage amplitude during an operation mode, the second voltage amplitude greater than the first voltage amplitude;
- and
- setting a threshold voltage of a comparator in a receiver to detect the first signal during the calibration mode and the second signal during the operation mode.
Dependencies are inferred from the claim text.