Single-Event Latchup Protection Simulator 2D

Ion Environment

Strike rate 6 /s

Supply voltage V_dd 5.0 V

Protection Circuit

Trip current I_trip 180 mA

Trip delay t_d 20.0 ms

Damage threshold E_dmg 0.90 J

Live Readouts

Latched now

Total current

0 mA

Protected

Destroyed

Strikes total

Alive dies

36 / 36

Legend

Idle die Latched (thyristor on) Just tripped / protected Destroyed

How it works

CMOS ICs contain a parasitic p-n-p-n structure (adjacent well/substrate diodes) that behaves like a thyristor. A heavy ion depositing enough charge along its track can forward-bias this structure into its low-impedance "on" state — single-event latchup (SEL) — which is a physical short, not a data error:

I_latch = (V_dd − V_hold) / R_latch
E(t)    = ∫ I_latch · V_dd dt     (Joule heating while latched)
destroyed if  E(t) > E_dmg  before the circuit breaker trips

Once latched, current stays high (bounded only by R_latch, not by the parasitic gate) until power is removed — an unprotected die self-heats until it fails. A current-limiting protection circuit watches supply current and cuts power once it exceeds I_trip continuously for the response delay t_d, then reconnects power after a cool-down. This is exactly the race modelled here.

Strike rate — Poisson-distributed ion hits across the array; higher V_dd also raises the trigger probability, matching real bias-dependence of the latchup window.
I_trip — set it too high and small latch currents never trip protection at all; too low and normal transients would false-trigger (not modelled, but the trade-off is real).
Trip delay t_d — a slower circuit lets more energy accumulate before cutoff; push it high enough and dies start cooking before the breaker reacts.
E_dmg — the die's own thermal damage budget; a fragile die (low E_dmg) needs a fast, low-threshold breaker to survive at all.

Click any die in the array below to open its thyristor inspector — a live cross-section of the pnpn structure with its own current and accumulated-energy readout. Real-world relevance: this is why spacecraft power rails use current-limiting FETs or fold-back regulators per board, not just fuses — a fuse is too slow, and this same physics is why radiation-hardened parts use epitaxial substrates and guard rings to raise the latchup trigger threshold in the first place.

Die array — click to inspect

Mission clock: 0.0 s

Total supply current vs. time (dashed = I_trip)

Thyristor inspector