Method and apparatus for calibrating a multi-level current mode driver
AssigneeRambus Inc.
InventorsCarl Werner, Mark Horowitz, Pak Chau, Scott Best, Stefanos Sidiropoulos
Life of this patent
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Abstract
A current controller for a multi-level current mode driver. The current controller includes a multi-level voltage reference and at least one source calibration signal. A comparator is coupled by a coupling network to the multi-level voltage reference and the at least one source calibration signal. A selected voltage is applied from the multi-level voltage reference and a selected source calibration signal is applied from the at least one source calibration signal to the comparator.
Claims21
A current controller for a multi-level current mode driver, comprising:
- a multi-level voltage reference adapted to supply a plurality of reference voltage levels;
- at least one source calibration signal;
- a comparator coupled by a coupling network to the multi-level voltage reference and the at least one source calibration signal;
- means for applying a selected voltage from the multi-level voltage reference and a selected source calibration signal from the at least one source calibration signal to the comparator;
- and
- means for adjusting the at least one source calibration signal in accordance with an output of the comparator.
A method of calibrating a multi-level current mode driver, comprising the steps of:
- Providing a first current sink and a second current sink;
- activating the first current sink to drive a known current through a load thereby producing a first input signal;
- activating the second current sink to produce a second input signal;
- calculating an average value of the first input signal and the second input signal;
- comparing the average value of the first input signal and the second input signal to a first known reference voltage;
- adjusting the second current sink, and thereby the second input signal, until the average value equals the known reference voltage;
- applying the adjusted second input signal as a new first input signal;
- activating the first current sink and a second current sink, thereby producing a precalibration voltage as a new second input signal;
- calculating an average value of the new first input signal and the new second input signal;
- comparing the average value of the new first input signal and the new second input signal to a second known reference voltage, wherein the second known reference voltage has a different value than the first known reference voltage;
- and
- adjusting the second current sink, and thereby the new second input signal, until the average value is equal to the second known reference voltage.
A current controller for a multiple pulse amplitude modulation (multi-PAM), drain-source conductance (gds) compensated current mode driver, comprising:
- a multiplexor having at least two distinct reference voltage inputs and a selectable output;
- a first output driver having at least two current control inputs and providing a first driver output, wherein at least one of the at least two current control inputs carries a current control signal that compensates for gds distortion in the first output driver;
- a second output driver having at least two current control inputs and providing a second driver output, wherein at least one of the at least two current control inputs carries a current control signal that compensates for gds distortion in the second output driver;
- a first circuit that provides an output that is an average of the first driver output and the second driver output;
- a second circuit that compares the selectable output to the average and provides an output in accordance with the comparison;
- and
- a third circuit coupled to the at least two current control inputs of the first output driver and the second output driver and coupled to receive the output of the second circuit, wherein the third circuit sets each of the at least two current control inputs in accordance with the output of the second circuit.
Dependencies are inferred from the claim text.