DAC Termination via Parallel Impedance Networks

Solution Overview

Problem

Digital-to-analog converters (DACs) face limitations due to increased output impedance, which restricts speed, introduces noise, and causes glitching, particularly in DAC circuits with series resistor connections.

Innovation Solution

The implementation of parallel impedance networks in DAC circuits, including termination impedance paths and switching networks, reduces alternating current (AC) impedance, enhances speed, and modifies the transfer function by selectively coupling voltage signals to generate an analog output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If series resistor connections are used in DAC circuits, then output impedance is increased, but speed is restricted and noise increases

Engineering Contradiction:

Improveoutput impedanceVSAvoidDAC speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent inverts the conventional series resistor connection to a parallel configuration. Instead of connecting resistors in series between the DAC output and ground, the patent connects resistors in parallel from the DAC output node to ground, fundamentally changing the impedance characteristics of the circuit.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the electrical parameters by using parallel resistor connections instead of series connections. This parameter change transforms the output impedance from high (series) to low (parallel), thereby improving speed and reducing noise while maintaining the voltage division functionality through adjusted resistance values.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If series resistor connections are used in DAC circuits, then output impedance is increased, but output noise increases

Engineering Contradiction:

Improveoutput impedanceVSAvoidoutput noise

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent inverts the conventional series resistor connection to a parallel configuration. Instead of connecting resistors in series between the DAC output and ground, the patent connects resistors in parallel from the DAC output node to ground, fundamentally changing the impedance characteristics of the circuit.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the electrical parameters by using parallel resistor connections instead of series connections. This parameter change transforms the output impedance from high (series) to low (parallel), thereby improving speed and reducing noise while maintaining the voltage division functionality through adjusted resistance values.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If series resistor connections are used in DAC circuits, then output impedance is increased, but settling time increases

Engineering Contradiction:

Improveoutput impedanceVSAvoidsettling time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent inverts the conventional series resistor connection to a parallel configuration. Instead of connecting resistors in series between the DAC output and ground, the patent connects resistors in parallel from the DAC output node to ground, fundamentally changing the impedance characteristics of the circuit.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the electrical parameters by using parallel resistor connections instead of series connections. This parameter change transforms the output impedance from high (series) to low (parallel), thereby improving speed and reducing noise while maintaining the voltage division functionality through adjusted resistance values.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10425098B2Digital-to-analog converter (DAC) termination

Publication Date: 2019.09.24 ANALOG DEVICES INT UNLTD CO

AI summary

Embodiments of the disclosure can provide digital-to-analog converter (DAC) termination circuits. A single or multiple parallel impedance networks can be coupled to a DAC to reduce the DAC's AC impedance, increase the DAC speed, and reduce the DAC settling time. The parallel impedance networks can be coupled to one or more of the DAC terminals in termination specific cases, or to nodes within the DAC. In an example, one-sided T-termination can be used with a single termination impedance path coupled in parallel with the DAC terminals, for reducing AC impedance at the DAC reference terminals, increasing speed, and reducing settling time. In an example, multiple impedance networks can be used in an H-bridge termination solution, which can be useful for high resolution DACs with or within a high voltage range.