TVS Diode Breakdown Voltage Margin for 24V Industrial I/O

Overview of Technical Issues:

The voltage-clamping structure (TVS diode) exhibits insufficient precision in its activation threshold relative to the 24V industrial I/O operating voltage—if the breakdown voltage margin is too narrow, normal voltage fluctuations cause harmful false triggering and circuit disruption; if too wide, transient surges transmit excessive voltage to protected components before clamping activates, risking damage; the goal is to optimize the breakdown voltage margin to reliably prevent false triggering during normal 24V operation while ensuring fast protection activation during actual surge events.

Solution directions generated for this problem

Problem Direction 1 :

ImproveBreakdown voltage threshold precision
VS
ConstraintManufacturing precision requirement

Inspiration 1 : Cross-domain reference

Application Principle: #26 Copying
Cross-domain applicability Assess applicability
Methods and systems for detecting genetic variants
Innovative Solution Refine solution

Post-fabrication laser trimming with digital voltage mapping for precision TVS threshold control

Manufacture TVS with standard tolerance then create precision copy via measurement
How to solve :
  • Fabricate TVS diodes using standard ±10% doping tolerance process to maintain high yield and low cost, avoiding precision wafer control
  • After fabrication, measure each device's actual breakdown voltage using automated curve tracer at 1mA test current, record voltage at ±0.1V precision, create digital voltage map as precision copy
  • Apply pulsed laser trimming (Nd:YAG 1064nm, 10ns pulses, 50μJ energy) to ablate thin surface layer of junction, shifting breakdown voltage by 0.3-0.5V per trim cycle until device falls within target ±2% bin (e.g., 27.0-27.5V for 24V application)
  • Final verification test confirms trimmed threshold under surge pulse (8/20μs waveform, 100A peak) with acceptance criteria: breakdown voltage within ±2% target, leakage current <10μA at 80% breakdown voltage, clamping voltage <35V at rated current
Expected Effect : Threshold precision ±2%, manufacturing yield >95%, cost increase <15% vs standard TVS
Risk Control :
  • laser energy variation causing over-trimming
  • thermal damage to junction integrity
  • long-term drift of trimmed threshold

Problem Direction 2 :

ImproveBreakdown voltage threshold precision
VS
ConstraintComponent screening complexity

Inspiration 1 : Cross-domain reference

Application Principle: #35 Parameter changes
Cross-domain applicability Assess applicability
System for characterizing tire uniformity machines and methods of using the characterizations
Innovative Solution Refine solution

Lithographically-defined electrode geometry clamp for precision voltage threshold

Replace doping-based TVS with geometry-controlled clamp
How to solve :
  • Replace avalanche-breakdown TVS with field-effect voltage clamp using lithographically-patterned electrodes — threshold set by electrode spacing (±0.5μm precision) rather than doping concentration (±10% variation)
  • Fabricate lateral MOSFET-based clamp with gate oxide breakdown at 30V±0.6V (±2% tolerance), using 5μm photolithography and 50nm thermal oxide — gate length 2.0±0.05μm controls threshold via capacitive coupling
  • Implement batch wafer-level testing using optical probing at 100 sites simultaneously — accept/reject entire wafer based on statistical process control (Cpk≥1.67 for 28-32V window), eliminating individual device binning
Expected Effect : Threshold tolerance ±2%, zero binning required, response time <500ns
Risk Control :
  • oxide breakdown uniformity across wafer
  • lithography alignment drift
  • gate oxide reliability under repetitive surge

Problem Direction 3 :

ImproveBreakdown voltage threshold precision
VS
ConstraintMust not deteriorate

Inspiration 1 : Cross-domain reference

Application Principle: #10 Preliminary action
Cross-domain applicability Assess applicability
Techniques for timers associated with powering receiver circuitry at a wireless device
Innovative Solution Refine solution

Pre-binned TVS inventory with voltage-class assignment for 24V protection

Pre-test and classify TVS diodes into narrow voltage bins before circuit assembly
How to solve :
  • Procure standard ±8% tolerance TVS diodes (26-32V nominal), test each unit at 1mA leakage current using automated curve tracer to measure actual breakdown voltage within ±0.5V accuracy
  • Sort devices into 1V increment bins (26.0-27.0V, 27.0-28.0V, 28.0-29.0V classes) using barcode labeling and segregated storage trays, creating pre-characterized inventory
  • During PCB assembly, select 27.5-28.5V bin devices for 24V circuits, ensuring 3.5V margin above 24V+15% (27.6V) and 6.5V margin below 35V surge threshold, achieving effective ±1.8% application tolerance without tightening fabrication process
Expected Effect : Threshold precision ±1.8%, false trigger rate <0.01%, surge response <1μs
Risk Control :
  • Automated testing throughput bottleneck
  • Inventory management of 6-8 voltage bins
  • Bin depletion causing production delays
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