Bandgap Startup Circuit With Hysteresis for Stable Reference Voltage

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Solution Overview

Problem

Bandgap reference circuits in semiconductor devices face variability issues due to process, voltage, and temperature variations, leading to inconsistent startup and reference voltage output, which affects the accuracy and efficiency of electronic devices.

Innovation Solution

A startup circuit with a comparator circuit, current mirror, and hysteresis circuit is integrated to stabilize the bandgap core circuit's output voltage by mirroring its operation and using feedback mechanisms to ensure consistent ramping across various PVT conditions, reducing oscillations and enabling accurate initialization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a startup circuit is used to initialize the bandgap reference circuit, then the output voltage can be ramped to a stable value, but the circuit becomes susceptible to process, voltage, and temperature variations causing inconsistent reference voltages

Engineering Contradiction:

Improvereference voltage consistencyVSAvoidPVT condition adaptability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The startup circuit performs preliminary action by pre-charging the bandgap core circuit before normal operation. The circuit uses a startup switch and current source to initially charge the output capacitor, ensuring the bandgap circuit reaches its operational voltage range before the feedback loop engages, thereby preventing startup failures under varying PVT conditions

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The circuit employs feedback mechanisms where the output voltage is monitored and fed back to control the startup switch and current source. When the output voltage reaches a predetermined threshold, the feedback signal turns off the startup switch, preventing over-charging and ensuring stable initialization across different process, voltage, and temperature conditions

Inventive Principle:

Principle #23Feedback

2Ease of manufacture

If circuit components are made susceptible to PVT variations for ease of manufacture, then manufacturing becomes simpler, but the bandgap reference circuit provides different reference voltages under various conditions

Engineering Contradiction:

Improvecircuit component fabricationVSAvoidreference voltage precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The circuit uses dynamic components such as switches and current sources that can adapt their operation based on real-time conditions. The startup switch dynamically controls the charging current based on the output voltage level, and the current source adjusts its output to maintain proper charging rates across different process and temperature conditions, ensuring precision despite manufacturing variations

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The circuit compensates for manufacturing variations by changing operating parameters dynamically. The startup current magnitude and duration are adjusted based on detected output voltage levels, allowing the circuit to achieve consistent reference voltages despite variations in component characteristics caused by different manufacturing processes

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the startup circuit ramps the output voltage quickly, then initialization time is reduced, but oscillations and time delays occur affecting accuracy

Engineering Contradiction:

Improveinitialization speedVSAvoidreference voltage accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The startup circuit employs periodic charging action through controlled current sources that charge the output capacitor in regulated intervals. The circuit uses a switch controlled by feedback signals to enable and disable the charging current, creating a controlled periodic action that prevents oscillations while maintaining fast initialization. This periodic control ensures the voltage ramps smoothly to the target level without overshooting or oscillating

Inventive Principle:

Principle #19Periodic action

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

The solution ensures consistent operation of bandgap circuits across a broader range of process, voltage, and temperature conditions, reducing time delays and oscillations, and allowing the bandgap circuit to maintain a stable reference voltage, enhancing the accuracy and efficiency of semiconductor devices.

Implementation Method 1

a hysteresis circuit is integrated to reduce oscillations

Methodology Applied

Scientific EffectHysteresis: Hysteresis

Implementation Method 2

Methodology Applied

Scientific EffectCurrent mirror effect:

Data Source

PatentUS11829177B2Systems and methods for initializing bandgap circuits

Publication Date: 2023.11.28 MICRON TECHNOLOGY INC

AI summary

A semiconductor device may include a bandgap circuit that outputs a reference voltage. The bandgap circuit may include a bandgap core circuit and a startup circuit coupled to the bandgap core circuit. The startup circuit may connect a voltage source to a node that corresponds to an output of the bandgap core circuit in response to the bandgap core circuit being initialized. The startup circuit may also disconnect the voltage source from the node in response to the output voltage being equal to or greater than a desired voltage (e.g., a threshold voltage) and one or more local voltages of the bandgap core circuit being equal to or greater than a local threshold voltage.