Switched capacitor multiplying digital-to-analog converter
AssigneeAnalog Devices, Inc.
InventorRalph D. Moore
Life of this patent
Estimating the term…
Abstract
Multiplying digital-to-analog converter (MDACs) are implemented in pipelined ADCs to generate an analog output being fed to a subsequent stage. A switched capacitor MDAC can be implemented by integrating a capacitor digital-to-analog converter (DAC) with charge pump gain circuitry. The capacitor DAC can implement the DAC functionality while the charge pump gain circuitry can implement subtraction and amplification. The resulting switched capacitor MDAC can leverage strengths of nanometer process technologies, i.e., very good switches and highly linear capacitors, to achieve practical pipelined ADCs. Moreover, the switched capacitor MDAC has many benefits over other approaches for implementing the MDAC.
Claims20
A switched capacitor multiplying digital-to-analog converter (MDAC) with open loop gain, comprising:
- a bank of capacitors, each capacitor having a first plate and a second plate, wherein:
- each one of the first plates of the bank of capacitors is connectable to a common mode voltage, a first voltage reference, and a second voltage reference, and
- the second plates of the bank of capacitors are connected to a common node connectable to receive a first one of complementary analog input signals;
- a gain capacitor having a first plate connectable to receive a second one of the complementary analog input signals and a second plate at a first complementary output of the switched capacitor MDAC;
- and
- a transfer switch to connect the common node to the first plate of the gain capacitor.
A method for residue generation, the method comprising:
- during a sample phase, connecting a first one of complementary analog input signals to a first plate of a gain capacitor, and connecting a second one of complementary analog input signals to a common node connecting first plates of capacitors within a capacitive digital-to-analog converter;
- and
- during a charge transfer phase, connecting the first plate of the gain capacitor to the common node, connecting each one of second plates of the capacitors within the capacitive digital-to-analog converter to a first reference or a second reference based on an output code controlling the capacitive digital-to-analog converter, and outputting a residue signal at a second plate of the gain capacitor.
A method for generating a residue in a pipelined analog-to-digital converter, comprising:
- converting an analog input signal to an output code;
- during a sampling phase, acquiring the analog input signal onto a top plate of a capacitor and a common node connecting top plates of capacitors within a capacitive digital-to-analog converter;
- and
- during a charge transfer phase,
- connecting each one of bottom plates of the capacitors within the capacitive digital-to-analog converter to a first voltage reference or a second voltage reference based on the output code;
- and
- connecting the top plate of the capacitor and the common node of the capacitive digital-to-analog converter.
Dependencies are inferred from the claim text.