Data rate tracking filter
AssigneeMarvell International Ltd.
InventorsYingxuan Li, Qing Yang
Life of this patent
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Abstract
The following embodiments relate to an analog filter having an adjustable transfer function for use in a system or circuit that processes a signal having a changing data rate. The transfer function may be adjusted by adjusting the resistance and/or capacitance of components of the analog filter. The analog filter is calibrated based on an optimum operational parameter at a certain data rate, such as a median data rate. The analog filter may be further adjusted as the data rate of the signal changes.
Claims17
A method for calibrating a first programmable resistor of a filter, the first programmable resistor having a resistance that is a function of an N-bit wide data input and an analog signal input, the method comprising:
- generating a current that is proportional to an input frequency;
- passing the current through a second programmable resistor with one or more characteristics that match the first programmable resistor to generate a voltage across the second programmable resistor;
- during a calibration stage:
- adjusting a value of an N-bit wide data input of the second programmable resistor until the voltage generated by the second programmable resistor matches a predetermined voltage;
- and
- setting the N-bit wide data input of the first programmable resistor to a same value as the value of the N-bit wide data input of the second programmable resistor.
An apparatus for controlling a first programmable resistor of a filter, the first programmable resistor having a resistance that is a function of an N-bit wide data input and an analog signal input, the apparatus comprising:
- a frequency-to-current circuit configured to generate a current that is proportional to an input frequency;
- a second programmable resistor having characteristics that match the first programmable resistor, wherein the second programmable resistor is configured to receive the generated current such that a voltage develops across the second programmable resistor;
- and
- a calibration circuit configured to place the apparatus into a calibration stage, wherein the calibration circuit in the calibration stage is configured to:
- adjust a value of an N-bit wide data input of the second programmable resistor until the voltage across the second programmable resistor matches a predetermined voltage;
- and
- set the N-bit wide data input of the first programmable resistor to a same value as the value of the N-bit wide data input of the second programmable resistor.
Dependencies are inferred from the claim text.