CMOS Bandgap Reference with Orthogonal Trimming

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Solution Overview

Problem

Existing bandgap voltage reference (BVR) circuits fail to provide necessary accuracy at low core voltages associated with Fin Field Effect Transistors (FinFET) technology, and lack independent control over voltage offset and temperature slope, which are critical for stable voltage references in VLSI circuits.

Innovation Solution

A low power voltage reference circuit that allows independent adjustment of voltage offset and temperature slope using a combination of Proportional To Absolute Temperature (PTAT) and Complementary To Absolute Temperature (CTAT) voltage devices, with a programmable temperature-independent current source and a PTAT current generator, enabling orthogonal trimming of output voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If standard bandgap voltage reference circuits are used, then temperature-independent voltage references are generated, but accuracy is insufficient at low core voltages (e.g., 0.75 V) associated with FinFET technology

Engineering Contradiction:

Improvevoltage reference accuracyVSAvoidoperating voltage level

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent changes the operating parameters of the bandgap voltage reference circuit by introducing separate programmable controls for voltage offset and temperature slope. This allows the circuit to be optimized for low voltage operation (e.g., 0.75 V) while maintaining accuracy through independent adjustment of these critical parameters, resolving the contradiction between low operating voltage and reference accuracy.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces dynamic programmability to the previously fixed bandgap reference circuit. By allowing runtime or one-time programming of voltage offset and temperature slope parameters, the circuit can adapt to different voltage conditions and process variations, enabling accurate operation at low core voltages where standard fixed designs fail.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If voltage offset and temperature slope are controlled together in standard BVR circuits, then circuit simplicity is maintained, but independent control over these parameters is lost

Engineering Contradiction:

Improveindependent parameter controlVSAvoidcircuit structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent segments the control of voltage offset and temperature slope into separate independent mechanisms. Instead of a single coupled control system, the invention introduces distinct programmable paths for adjusting each parameter, allowing independent optimization of voltage offset through one mechanism and temperature slope through another, thereby achieving ease of operation with independent control.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent adds a new dimension of control by introducing programmability as an additional degree of freedom. By incorporating digital or analog programming interfaces that operate independently of the core bandgap generation mechanism, the circuit gains the ability to separately adjust voltage offset and temperature slope without complicating the fundamental bandgap operation.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables the generation of stable, temperature-independent voltage references that can operate at low voltages, such as 0.75 V, and allows for independent control of voltage offset and temperature slope, addressing the limitations of standard BVR circuits in FinFET contexts.

Implementation Method 1

a temperature-independent current source that is separately programmable from a second, temperature-dependent current source

Methodology Applied

Scientific EffectTemperature-independent current generation:

Implementation Method 2

The voltage temperature slope may be the combination of Proportional To Absolute Temperature (PTAT) voltage and Complementary To Absolute Temperature (CTAT) voltage devices

Methodology Applied

Scientific EffectProportional To Absolute Temperature voltage generation: Seebeck Effect

Implementation Method 3

The voltage temperature slope may be the combination of Proportional To Absolute Temperature (PTAT) voltage and Complementary To Absolute Temperature (CTAT) voltage devices

Methodology Applied

Scientific EffectComplementary To Absolute Temperature voltage generation: Seebeck Effect

Data Source

PatentUS9696744B1CMOS low voltage bandgap reference design with orthogonal output voltage trimming

Publication Date: 2017.07.04 SYNOPSYS INC

AI summary

Bandgap Voltage Reference circuits configured to produce reference voltages with both voltage offset and a voltage temperature slope are disclosed. By generating the voltage offset from a temperature-independent current, the voltage offset of the reference voltage may be temperature-independent, while generating the voltage temperature slope from a temperature-dependent current allows the voltage temperature slope to vary with temperature. To ensure that the voltage offset remains independent from the voltage temperature slope, an apparatus is disclosed for orthogonal trimming of voltage offset and voltage temperature slope.