Level shifter and method of calibration
First Claim
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1. 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.
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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.
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Citations
20 Claims
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1. A circuit comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of calibrating a level shifter, the method comprising:
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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. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A method comprising:
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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. - View Dependent Claims (17, 18, 19, 20)
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Specification