Ramp voltage generator and method for testing an analog-to-digital converter
AssigneeFreescale Semiconductor, Inc.
InventorsXiankun Jin, Douglas A. Garrity
Life of this patent
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Abstract
A method and circuit for generating ramped voltages are provided. The ramp voltage generator circuit includes: a switched-capacitor amplifier having an input terminal, an output terminal, a sampling capacitor switchably coupled to the input terminal, and a gain capacitor switchably coupled to the output terminal; and a current source having a terminal coupled to a supply terminal, and a terminal coupled to the input terminal. The ramp voltage generator circuit may be coupled to test an analog-to-digital converter (ADC).
Claims19
A ramp voltage generator comprising:
- a switched-capacitor amplifier having a first input terminal, a first output terminal, a first sampling capacitor having a first terminal switchably coupled to the first input terminal, and a first gain capacitor having a first terminal switchably coupled to the first output terminal;
- a first current source having a first terminal coupled to a first supply terminal, and a second terminal coupled to the first input terminal;
- a first switch having a first terminal coupled to a second supply terminal, and a second terminal coupled to the first terminal of the first sampling capacitor;
- a second switch having a first terminal coupled to the second supply terminal, and a second terminal coupled to a second terminal of the first sampling capacitor;
- and
- a third switch having a first terminal coupled to the second supply terminal, and a second terminal coupled to the first terminal of the first gain capacitor.
A ramp voltage generator comprising:
- a first current source having a first terminal coupled to a first supply terminal, and a second terminal;
- a first switch having a first terminal coupled to the second terminal of the first current source, and a second terminal;
- a second switch having a first terminal coupled to a second supply terminal, and a second terminal coupled to the second terminal of the first switch;
- a third switch having a first terminal coupled to the second supply terminal, and a second terminal;
- a fourth switch having a first terminal and a second terminal;
- a first capacitor having a first terminal coupled to the second terminal of the first switch, and a second terminal coupled to the second terminal of the third switch;
- a second capacitor having a first terminal coupled to the second terminal of the first capacitor, and a second terminal coupled to the first terminal of the fourth switch;
- and
- an amplifier having a first input coupled to the second terminal of the first capacitor, and a first output coupled to the second terminal of the fourth switch.
A method for generating a ramped voltage, the method performed in a ramp voltage generator circuit including an output terminal, a current source, a first capacitor, a second capacitor, an offset generation circuit, and an amplifier having a first input and a first output, the method comprising:
- during a first phase having a first configuration of a plurality of switches, charging the first capacitor using the current source;
- during a second phase having a second configuration of the plurality of switches, transferring charge from the first capacitor to the second capacitor such that a change in charge at the second capacitor causes a first predetermined voltage change at the output terminal;
- and
- during a third phase having a third configuration of the plurality of switches, transferring charge from the offset generation circuit to the second capacitor such that a change in charge at the second capacitor causes a second predetermined voltage change at the output terminal.
Dependencies are inferred from the claim text.