On-chip emulation of large resistors for integrating low frequency filters
AssigneeVidatronic, Inc.
InventorAnand Veeravalli Raghupathy
Life of this patent
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Abstract
A system for processing of signals with poles that are low in frequency includes a switched capacitor circuit that includes two switches connected to an input and an output of a switching capacitor (Cs), respectively, in an alternating manner at a selected switching frequency (fSW); and a filter capacitor connected between an input and the switched capacitor circuit. The filter capacitor and the switched capacitor circuit together function as a filter, thereby a pole frequency depending on a ratio of capacitance of the switching capacitor (Cs) and the filter capacitor, instead of an RC product.
Claims8
A system for processing of signals with poles that are low in frequency, comprising:
- a switching capacitor circuit network comprising two switches connected to an input and an output of a switching capacitor (Cs), respectively, in an alternating manner at a selected frequency (fSW), wherein the switching capacitor circuit network is connected to a common mode reference of the system and is used for fixing a DC bias level of the system;
- and
- a filter capacitor (CHPF) connected between an input and the switching capacitor circuit network, wherein the filter capacitor and the switching capacitor circuit network together function as a fully integrated on-chip filter,
- thereby resulting in a pole frequency depending on a ratio of capacitance of the switching capacitor circuit network and the filter capacitor (CHPF), wherein a capacitance of the filter capacitor is substantially larger than a capacitance of the switching capacitor,
- wherein the system is fully integrated on chip using an advanced process node of ≤20 nm.
A method for implementing ultra large resistance on-chip without physical use of a resistor component that is sensitive to pA levels of leakage and that is either not available in advanced process nodes ≤20 nm or prohibitive in die area cost due to lack of high sheet resistance components, to allow integration of a large external de-coupling capacitor for realizing a fully integrated on-chip filter pole that is low in frequency, comprising;
- a. using a switching capacitor circuit network to implement the ultra large resistor, wherein the switching capacitor circuit network comprises two switches connected to an input and an output of a switching capacitor (Cs), respectively, in an alternating manner at a selected frequency (fSW), wherein the switching capacitor circuit network is connected to a common mode reference of a system and is used for fixing a DC bias level of the system, and wherein a filter capacitor (CHPF) is connected between an input and the switching capacitor circuit network;
- and
- b. setting a pole frequency to be a function of a ratio of capacitance of the filter capacitor (CHPF) and the switching capacitor (Cs), instead of a RC product, wherein a capacitance of the filter capacitor is substantially larger than a capacitance of the switching capacitor,
- thereby attenuating an impact of switching noise by the ratio of capacitance of the capacitors.
Dependencies are inferred from the claim text.