Source-linked AI summary
Design of a Fast Crowbar Protection Circuit for Single Event Effect Testing
Collin Burt, Joseph D'Amico, Joseph Van Grinsven, Tommy Aldaz, Nathaniel Dodds
TL;DR
Destructive SEL/SEB tests can require frequent device replacement, increasing labor, time, and cost. The paper designs a programmable crowbar that detects overvoltage or overcurrent, conditions the fault signal with a 555 Timer, and rapidly disconnects and grounds the DUT supply. Benchtop tests demonstrated general functionality, while SEL/SEB experiments were ongoing at the time of writing.
Problem
Destructive latchup or burnout during SEE testing can require large numbers of samples and frequent device replacement for cross-section, safe-operating-area, and sensitive-region measurements.
Method
The paper designs a crowbar placed between the supply and DUT that detects programmable overvoltage or overcurrent conditions, delays actuation with a 555 Timer, and disconnects and grounds the DUT input.
Results
Benchtop testing verified general functionality, including crowbar power-cut operation after an emulated high-current event.
Takeaways & Limitations
The circuit is expected to let one DUT undergo repeated nondestructive SEL testing instead of being continuously replaced after destructive events.
Abstract
from arXiv · showhide
We describe the design of a custom crowbar circuit that quickly removes power when a programmable current threshold is exceeded. This protects devices from permanent damage during single event latchup/burnout tests.
I. INTRODUCTION
Destructive SEL/SEB testing can require many device samples and repeated replacement, increasing time and cost. The paper introduces a custom crowbar circuit to address this testing challenge.
- I. INTRODUCTION: Destructive latchup or burnout makes SEL/SEB testing labor intensive because damaged devices must be frequently replaced.Such testing may require large numbers of samples, delaying experiments and increasing cost.
- I. INTRODUCTION: The circuit is intended for tests that measure SEL/SEB cross sections, establish safe operating areas, or locate sensitive regions.
A. Crowbar Circuit
The crowbar is inserted between the supply and DUT to disconnect power and ground the DUT input when an unsafe condition is detected.
- A. Crowbar Circuit: The crowbar sits between the power supply and DUT, monitoring for overvoltage or overcurrent conditions.
- A. Crowbar Circuit: Upon detection, it rapidly cuts DUT power by breaking the supply connection and connecting the DUT input to ground.
C. Overvoltage and Overcurrent Protection
Separate voltage and current detectors provide programmable fault thresholds for the crowbar protection system. Voltage is divider-compared to a reference, while current is sensed, amplified, and compared to another reference.
- C. Overvoltage Protection: Overvoltage detection monitors the input through a voltage divider and compares it with a reference voltage.The threshold is set by adjusting the voltage-divider ratios.
- C. Overvoltage Protection: The overvoltage threshold is set by adjusting the voltage divider ratios.
- C. Overcurrent Protection: Overcurrent detection measures voltage across Rsense, amplifies it with the IN185A1, and sends it to a comparator with a built-in reference.The overcurrent threshold is set by the Rsense resistor.
- C. Protection Schematics: Figures 3 and 4 provide the overvoltage and overcurrent detection schematics, respectively.
D. 555 Timer
The 555 Timer conditions detector outputs before crowbar actuation, preventing rapid power cycling while providing adjustable or manually controlled fault duration and user alerts.
- D. 555 Timer: An OR gate combines overvoltage and overcurrent signals before a 555 Timer in monostable configuration initiates crowbar action.This avoids oscillations that could rapidly power cycle the DUT.
- D. 555 Timer: The 555 Timer introduces a fixed, adjustable delay, with switches allowing manual reset and indefinite state holding.Delay changes use resistor and capacitor values.
- D. 555 Timer: The timer output passes through transistor buffers before driving the crowbar transistors.
- D. 555 Timer: The indicator circuit compares the timer output with a reference to activate an LED and buzzer when the crowbar actuates.
E. Powerup Delay Circuit
The powerup delay circuit prevents startup inrush current from prematurely triggering overcurrent protection by delaying 555 Timer activation until the output reaches a programmable reference.
- Powerup Delay Circuit: Startup inrush current can prematurely trigger overcurrent detection and prevent the output from charging.The circuit addresses this problem during powerup.
- Powerup Delay Circuit: An output-voltage comparator drives a transistor through an RC filter that introduces the startup delay.The comparator uses a programmable reference voltage.
- Powerup Delay Circuit: After the powerup delay, the circuit enables the 555 Timer to respond to overvoltage or overcurrent events.The delay keeps the trigger disabled during startup.
- Powerup Delay Circuit: The powerup delay circuit is presented as a dedicated schematic in Figure 7.
F. Final Circuit Design
The final design combines the protection subcircuits into a single-channel crowbar, replicates it across three voltage rails, and verifies operation through benchtop testing.
- F. Final Circuit Design: The final circuit combines the preceding subcircuits to protect a single voltage rail.The design is shown in the single-channel crowbar schematic.
- F. Final Circuit Design: Three replicated channels protect 0.8V, 1.8V, and 3.3V rails using different program components.A 12V supply drives the high-side FETs, while a linear regulator provides 5V for the integrated circuits.
- F. Final Circuit Design: Benchtop testing emulates a high-current event by connecting an uncharged capacitor to the DUT output.The resulting excess-current burst trips overcurrent protection and initiates the crowbar function.
- F. Final Circuit Design: The 3.3V test measures the delay from output disruption to crowbar power cutoff.The test result is reported in Figure 11.
- F. Final Circuit Design: The powerup-delay circuitry is connected to the 555 Timer trigger in the final implementation.This connection is shown in Figure 9.
III. CONCLUSIONS
The work presents a fast crowbar circuit for protecting devices during single-event latchup and burnout testing. Benchtop tests demonstrated general functionality, while single-event testing was still underway.
- III. CONCLUSIONS: The circuit is designed to protect devices against high-current latchup or burnout during single-event-effects testing.
- III. CONCLUSIONS: Benchtop testing demonstrated the circuit’s general functionality.
- III. CONCLUSIONS: Single-event testing was being performed to evaluate protection in an actual advanced-node CMOS test environment.
- III. CONCLUSIONS: The 0.8V simulation shows 555 Timer output and crowbar voltage/current action during detected overcurrent or overvoltage events.
- III. CONCLUSIONS: The 3.3V test data show the delay between an overcurrent disturbance and crowbar output-power cutoff.