Case Studies

Structured engineering narratives covering context, constraints, architecture decisions, and verification outcomes from representative advisory engagements.

Biphasic Stimulation Architecture

Architecture advisory for a charge-balanced therapeutic stimulation system requiring safety-critical output control.

Problem

The engineering team had developed a functional prototype of a biphasic stimulation system for therapeutic neuromodulation. While the prototype demonstrated correct output waveforms under nominal conditions, the architecture lacked formal safety boundaries between the high-voltage output stages and digital control logic. There was no structured approach to ensuring charge balance under fault conditions.

Constraints

The system operated at voltages capable of causing tissue damage if charge balance was lost. Regulatory expectations required demonstrable safety interlocks independent of the primary control firmware. The team had limited experience with safety-critical architecture patterns and needed to maintain their existing development timeline.

Architecture Decisions

Introduced a dual-path architecture separating the waveform generation logic from an independent safety monitor subsystem. The safety monitor was designed to verify charge balance and timing parameters independently of the main control path. Defined explicit interface contracts between the high-voltage domain and digital control domain, with hardware-enforced fault containment at domain boundaries.

Failure Considerations

Analyzed failure modes including timing drift between control and output stages, firmware hang conditions during active stimulation, and power supply transients affecting charge balance accuracy. Designed hardware interlocks that could terminate output independently of firmware state. Established worst-case charge accumulation budgets for all identified fault scenarios.

Verification Strategy

Defined a verification approach based on fault injection at domain boundaries, timing margin analysis under worst-case operating conditions, and charge balance measurement under representative fault scenarios. Verification artifacts were mapped to specific safety claims to support regulatory evidence requirements.

High-Voltage Piezo Driver Systems

System architecture review for a precision high-voltage piezo actuation platform experiencing intermittent field failures.

Problem

A precision piezo actuation system was experiencing intermittent failures in deployed units that could not be reproduced reliably in the laboratory. The failures manifested as unexpected output behavior and occasional drive-circuit protection trips. The engineering team had exhausted component-level debugging and suspected a system-level architecture issue.

Constraints

The system operated at voltages exceeding 200V with precision timing requirements in the microsecond range. Thermal management was critical due to high duty-cycle operation. The existing PCB layout and enclosure design had limited modification headroom, requiring solutions that worked within the current physical architecture.

Architecture Decisions

Restructured the interface design between the high-voltage drive domain and the low-voltage control electronics. Introduced explicit voltage domain isolation with defined creepage and clearance boundaries. Redesigned the fault detection architecture to distinguish between transient protection trips and genuine fault conditions, reducing false shutdowns while maintaining safety coverage.

Failure Considerations

Root-cause analysis traced the intermittent failures to inadequate fault isolation at domain boundaries, where high-voltage transients were coupling into control-side signal paths through shared ground references. Thermal analysis revealed that sustained high-duty-cycle operation was degrading isolation characteristics over time, explaining the intermittent and deployment-dependent nature of the failures.

Verification Strategy

Established a thermal-stress verification protocol that replicated field operating profiles. Defined boundary-scan verification for domain isolation under combined thermal and electrical stress. Created a regression test suite targeting the specific fault coupling mechanism to prevent reintroduction in future design revisions.

Biomedical Signal Acquisition Platform

Architecture and verification strategy for a multi-channel biosignal acquisition system transitioning from research prototype to clinical product.

Problem

A multi-channel biosignal acquisition system had been developed as a research prototype with excellent signal quality under controlled laboratory conditions. The transition to a clinical product required the architecture to maintain signal integrity across a wider range of operating environments, patient interfaces, and electromagnetic conditions while meeting regulatory evidence requirements.

Constraints

The signal chain operated at microvolt-level resolution with strict noise budgets. The system needed to handle variable electrode impedances and motion artifacts without compromising diagnostic accuracy. The firmware had to support deterministic data acquisition across all channels simultaneously while managing real-time data transfer to the host application.

Architecture Decisions

Restructured the analog front-end architecture with explicit noise budget allocation across each stage of the signal chain. Introduced a firmware architecture based on deterministic acquisition scheduling with hardware-triggered sampling to eliminate software timing jitter. Defined clear interface boundaries between the acquisition subsystem, digital processing pipeline, and host communication layer.

Failure Considerations

Analyzed failure modes including electrode disconnect detection, signal saturation recovery, and data integrity under communication bus contention. Designed graceful degradation behavior for individual channel failures that preserved the diagnostic value of remaining channels. Established monitoring points for real-time signal quality assessment.

Verification Strategy

Defined a verification approach centered on signal integrity measurements under representative operating conditions including simulated patient interfaces, ambient electromagnetic environments, and concurrent system loading. Mapped verification evidence to specific performance claims required for the regulatory submission. Established acceptance criteria for noise floor, common-mode rejection, and cross-channel isolation.