US 10,069,483 B1Granted

Multi-path analog system with multi-mode high-pass filter

AssigneeCirrus Logic, Inc.

InventorsRamin Zanbaghi, Siladitya Dey, Daniel J. Allen, John L. Melanson, Aniruddha Satoskar

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Abstract

A system may comprise a high-pass filter having an input for receiving an input signal, an output for generating an output signal, a capacitor coupled between the input and the output, a switched-capacitor resistor coupled between the output and a reference voltage, and control circuitry configured to control the reference voltage to cancel current leakage into a circuit coupled to the output. The input, the output, the capacitor, and the switched-capacitor resistor may be arranged to generate the output signal as a high-pass filtered version of the input signal and the high-pass filter may be configured to operate in a plurality of modes comprising at least a high-impedance mode and a low-impedance mode in which the resistance of the switched-capacitor resistor is significantly smaller than the resistance when in the high-impedance mode.

Claims74

Dependent claims

A system comprising:

a plurality of processing paths comprising:
a first processing path configured to generate a first digital signal based on an analog input signal;
and
a second processing path configured to generate a second digital signal based on the analog input signal;
and
control circuitry for determining weighted proportions of the first digital signal and the second digital signal to be combined into an output digital signal based on a characteristic of the analog input signal;
wherein the second processing path includes a high-pass filter for filtering the analog input signal prior to the analog input signal being processed by the remainder of the second processing path, the high-pass filter comprising:
an input for receiving an input signal;
an output for generating an output signal;
a capacitor coupled between the input and the output;
and
a switched-capacitor resistor coupled to the output;
and
further wherein:
the input, the output, the capacitor, and the switched-capacitor resistor are arranged to generate the output signal as a high-pass filtered version of the input signal;
and
the high-pass filter is configured to operate in a plurality of modes comprising at least:
a first mode in which the control circuitry causes the switching frequency of switched capacitors of the switched-capacitor resistor to be approximately equal to an integer multiple of a sample rate of an analog-to-digital converter receiving the output signal such that the switched-capacitor resistor has a first resistance;
and
a second mode in which the switched-capacitor resistor has a second resistance significantly smaller than first resistance.

17 more elements

A method comprising:

processing an analog input signal with a first processing path to generate a first digital signal based on the analog input signal;
processing the analog input signal with a second processing path to generate a second digital signal based on the analog input signal;
determining weighted proportions of the first digital signal and the second digital signal to be combined into an output digital signal based on a characteristic of the analog input signal;
high-pass filtering, with a high-pass filter, the analog input signal prior to the analog input signal being processed by the remainder of the second processing path, the high-pass filter comprising:
an input for receiving an input signal;
an output for generating an output signal;
a capacitor coupled between the input and the output;
and
a switched-capacitor resistor coupled to the output;
wherein the input, the output, the capacitor, and the switched-capacitor resistor are arranged to generate the output signal as a high-pass filtered version of the input signal;
and
operating the high-pass filter in a plurality of modes comprising at least:
a first mode in which the switching frequency of switched capacitors of the switched-capacitor resistor is approximately equal to an integer multiple of a sample rate of an analog-to-digital converter receiving the output signal such that the switched-capacitor resistor has a first resistance;
and
a second mode in which the switched-capacitor resistor has a second resistance significantly smaller than first resistance.

12 more elements

A system comprising:

a plurality of processing paths comprising:
a first processing path configured to generate a first digital signal based on an analog input signal;
and
a second processing path configured to generate a second digital signal based on the analog input signal;
and
control circuitry for determining weighted proportions of the first digital signal and the second digital signal to be combined into an output digital signal based on a characteristic of the analog input signal;
wherein the second processing path includes a high-pass filter for filtering the analog input signal prior to the analog input signal being processed by the remainder of the second processing path, the high-pass filter comprising:
an input for receiving an input signal;
an output for generating an output signal;
a capacitor coupled between the input and the output;
and
a switched-capacitor resistor coupled to the output;
and
further wherein:
the input, the output, the capacitor, and the switched-capacitor resistor are arranged to generate the output signal as a high-pass filtered version of the input signal;
and
the high-pass filter is configured to operate in a plurality of modes comprising at least:
a first mode in which the control circuitry causes the switching frequency of switched capacitors of the switched-capacitor resistor to be such that the switched-capacitor resistor has a first resistance;
a second mode in which the switched-capacitor resistor has a second resistance significantly smaller than the first resistance;
and
a third mode in which the switching frequency is a maximum frequency to enable a quick charging of the output of the high-pass filter.

18 more elements

A method comprising:

processing an analog input signal with a first processing path to generate a first digital signal based on the analog input signal;
processing the analog input signal with a second processing path to generate a second digital signal based on the analog input signal;
determining weighted proportions of the first digital signal and the second digital signal to be combined into an output digital signal based on a characteristic of the analog input signal;
high-pass filtering, with a high-pass filter, the analog input signal prior to the analog input signal being processed by the remainder of the second processing path, the high-pass filter comprising:
an input for receiving an input signal;
an output for generating an output signal;
a capacitor coupled between the input and the output;
and
a switched-capacitor resistor coupled to the output;
wherein the input, the output, the capacitor, and the switched-capacitor resistor are arranged to generate the output signal as a high-pass filtered version of the input signal;
and
operating the high-pass filter in a plurality of modes comprising at least:
a high-impedance mode in which the switching frequency of switched capacitors of the switched-capacitor resistor is such that the switched-capacitor resistor has a first resistance;
a low-impedance mode in which the switched-capacitor resistor has a second resistance significantly smaller than the first resistance;
and
a quick charge mode in which the switching frequency is a maximum frequency to enable a quick charging of the output of the high-pass filter.

13 more elements

Dependencies are inferred from the claim text.