Comparator-based buffer with resistive error correction
AssigneeAsahi Kasei Microdevices Corporation
InventorsJeongseok Chae, Gábor C Temes
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Abstract
A comparator-based buffer method and system enhance the driving capability of high-gain amplifiers with switched-capacitor loads. It includes a current source, a comparator, switches, sampling capacitor and overshoot correction resistor. A correction solution using a resistor in the charging path and a correction phase reduces the overshoot of the output voltage while constraining power consumption and minimizing components. Spectre® simulations verify the effectiveness of the invention.
Claims20
A buffer comprising:
- an input terminal;
- an output terminal;
- a comparator comprising a first, positive, terminal, wherein said first positive terminal is connected to said input terminal;
- a resistor in a charging path which is between a second negative terminal of said comparator and said output terminal;
- a current source which supplies a current to said resistor;
- a first switch which is connectable between said second, negative, terminal and said output terminal through said resistor, wherein said first switch is controlled by said comparator;
- a second switch which is connectable between said input terminal and said output terminal, wherein said second switch in a reversed phase of said first switch is controlled by said comparator;
- and
- a third switch which resets a voltage of said first negative terminal.
A comparator-based buffer comprising:
- at least a comparator;
- a current source;
- a switch for cancelling overshoot value of time delay of said comparator;
- and
- a resistor in a charging path, wherein said resistor generates a constant difference between a negative terminal of said comparator and an output terminal of said comparator, for compensating said overshoot.
A system for high gain amplifiers to drive a switched capacitor load comprising:
- a buffer section comprising:
- a high gain amplifier input;
- a current source;
- a comparator;
- at least a first switch, a second switch, and a resistor in a charging path;
- and
- an analog to digital converter (ADC) section comprising:
- a sampling capacitor;
- wherein when a second phase rises, said sampling capacitor is discharged and reset to ground when a first phase rises and a third phase rises, voltage VA resets, and output of said comparator turns on said first switch connected to said current source,
- when said third phase falls, said sampling capacitor charges to input voltage Vin,
- when said voltage VA exceeds said input voltage Vin, said first switch opens and output of said high gain amplifier is connected directly to input of said sampling capacitor of said ADC through said second switch, reducing overshoot error, and
- when said second phase rises, charge on said sampling capacitor is delivered to said ground and an amplifier of said ADC.
A method for use with a high gain amplifier to drive a switched capacitor load, said method comprising the steps of:
- discharging at least one sampling capacitor when a second phase Φ2 rises;
- resetting voltage VA, and turning on at least a first switch by a comparator output when a first phase Φ1 and a third phase ΦS rise;
- charging said sampling capacitor to voltage Vin when said third phase ΦS falls;
- opening said first switch when said voltage VA exceeds said voltage to Vin;
- and
- delivering charge of said at least one sampling capacitor to virtual ground and an amplifier of an analog to digital converter (ADC) section when said second phase Φ2 rises.
Dependencies are inferred from the claim text.