SPI Preregulator Circuit for Negative Power Transient Stability

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Solution Overview

Problem

In electronic systems using serial peripheral interfaces, maintaining consistent logic thresholds during power transients is challenging, especially in automotive applications where negative power supply transients can cause high current draw and power supply voltage drops, potentially leading to controller shutdown.

Innovation Solution

A high-side switch circuit with a preregulator circuit, input and output buffer circuits, and a control circuit that includes transistors and Zener diodes to regulate and isolate voltages, ensuring stable operation during power transients by limiting voltage fluctuations and maintaining appropriate logic states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the circuit uses standard voltage regulation during power transients, then the regulation response is slow, but the voltage fluctuations cause logic threshold inconsistencies and controller shutdown

Engineering Contradiction:

Improvelogic threshold consistencyVSAvoidvoltage regulation response speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The preregulator circuit is activated before the main voltage regulator to preemptively establish stable voltage levels. During power transients, the preregulator responds immediately to clamp voltage excursions before they can affect the digital core circuitry, ensuring logic thresholds remain consistent while the main regulator catches up.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The voltage regulation function is divided into two independent circuits: a preregulator circuit for immediate transient response and a main voltage regulator for steady-state regulation. This segmentation allows each circuit to be optimized for its specific function, with the preregulator providing fast protection and the main regulator providing stable long-term operation.

Inventive Principle:

Principle #1Segmentation

2Speed

If the circuit allows fast voltage changes during transients, then the response time is reduced, but the current draw increases and causes power supply voltage drops

Engineering Contradiction:

Improvetransient response timeVSAvoidcurrent draw during transients

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The preregulator circuit acts as an intermediary between the power supply and the digital core circuitry during transients. It absorbs the initial voltage transient energy through its transient response mechanism, preventing direct high current draw from the power supply while still protecting the sensitive logic circuits from voltage fluctuations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The preregulator circuit provides beforehand cushioning by being pre-positioned to immediately counteract voltage transients before they propagate to the main circuitry. This cushioning effect reduces the severity of transients that reach the power supply and digital core, thereby reducing peak current draw and preventing power supply voltage drops.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If the circuit uses complex voltage isolation, then the voltage stability during transients is improved, but the circuit complexity increases

Engineering Contradiction:

Improvevoltage stability during transientsVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The preregulator circuit is designed to perform multiple functions: it provides immediate transient response, establishes preliminary voltage regulation, and protects the digital core circuitry. By consolidating these functions into a single circuit block with a relatively simple structure, the design achieves high voltage stability without proportionally increasing circuit complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 circuit maintains stable voltage levels and reduces current draw during negative power supply transients, preventing controller shutdown and ensuring reliable communication and operation of high-side switches.

Implementation Method 1

The first Zener diode has a first terminal coupled to the second terminal of the first transistor, and a second terminal coupled to the control terminal of the first transistor. The second Zener diode has a first terminal coupled to the control terminal of the second transistor, and a second terminal coupled to the second terminal of the first Zener diode.

Methodology Applied

Scientific EffectZener breakdown: Avalanche Breakdown

Data Source

PatentUS20260005690A1Serial peripheral interface

Publication Date: 2026.01.01 TEXAS INSTRUMENTS INC

AI summary

A circuit includes a preregulator circuit. The preregulator circuit includes first and second transistors, and first and second Zener diodes. The first transistor has a first terminal, a second terminal, and a control terminal. The first Zener diode has a first terminal coupled to the second terminal of the first transistor, and a second terminal coupled to the control terminal of the first transistor. The second transistor has a first terminal coupled to the second terminal of the first transistor, a second terminal, and a control terminal coupled to the first terminal of the first transistor. The second Zener diode has a first terminal coupled to the control terminal of the second transistor, and a second terminal coupled to the second terminal of the first Zener diode.