Rad-Tolerant / Space LDO — Selection & Validation Guide

Budget mission dose realistically and apply 1.5× to 2× design margin. Verify with curves, not single points, across temperature and bias. Acceptable drift bands must be defined for Vout, Iq, dropout, and PSRR. If data only exists at HDR, add extra conservatism for long LDR exposure.

LET_th is the threshold where latch-up stops occurring; LET_max is the highest tested level without destructive effects. Choose devices whose LET_th exceeds your environment and confirm protection: current limit, power-cycle timing, and thermal margins. If only LET_max is stated, treat immunity as uncertain.

LDR testing usually reflects long mission exposure more closely, but you still need HDR data to de-risk process sensitivity. Compare both sets for parameter drift trends. If only HDR is available, increase margin and plan an engineering test campaign with representative temperature and bias conditions.

Define frequency points (100 Hz, 10 kHz, 1 MHz) and a noise bandwidth (e.g., 10–100 kHz). Require drift curves at each dose step. Re-measure stability and phase margin with post-TID capacitors. If noise rises into ADC bands, add a secondary low-noise stage or RC/π filtering.

Use a start-up profile tolerant of pre-biased outputs and place ideal-diode OR-ing or reverse blocking where rails can interact. Confirm discharge paths and soft-start ramp avoid reverse current. Validate with scoped transients under worst-case cable resistance and temperature corners.

Place the filter after the regulator where load sensitivity is highest and size the cutoff above the control loop bandwidth but below expected SET energy. Reference feedback RC to AGND and re-check phase margin with injection. Tune snubbers only with measured waveforms, not estimates.

Limit quickly to protect silicon and thermals, then enforce a power-off interval long enough to clear parasitic conduction. Re-enable with an idempotent boot sequence. Keep SEL recovery independent from A/B source switchover to avoid tug-of-war between redundant rails.

Partition analog and power grounds and make a single-point tie near the regulator ground pin or sense return. Keep feedback, reference, and sense networks in the AGND island. Route high di/dt returns in PGND and avoid cross-currents through sensitive nodes.

Don’t share sense traces with power currents or route them near switching edges. Keep the pair tightly coupled and equal length to the load pads. Place the sense RC at the amplifier side and reference it to AGND. Validate with load-step measurements at temperature extremes.

Use two stages when radiation limits noise/PSRR performance, or when a sensitive ADC/RF block needs a quieter local domain. Make the outer stage space-qualified and the inner stage focused on noise. Ensure start-up ordering and drop-out stacking remain valid across temperature.

Sample each lot with reduced TID dose points and at least one SEE condition covering SEL susceptibility. Compare against development reference curves with predefined drift windows. Deliver raw CSV logs, waveforms, setup photos, and a signed acceptance form with lot IDs and screening grades.

Normalize each metric versus nominal and weight by mission criticality. Penalize drift beyond acceptance bands and count event density for SEL/SET. Use a rolling window to smooth noise and store pre-trigger history for context. Score ranges should map to action: observe, retest, or replace.

It depends on the architecture, but reference drift and loop gain reduction often degrade PSRR before noise hits user limits. Always compare curves at defined frequency points and re-validate stability. If PSRR is marginal, add post-filtering or a cascaded low-noise regulator.

Choose QML-V/ESCC when mission risk and process assurance dominate or your customer mandates it. Choose Rad-Tolerant with third-party reports for cost- or schedule-driven prototypes, but document limitations, add larger margins, and perform your own validation to mission-like conditions.

Use pre-trigger RAM, periodic snapshots, and wear-aware storage. On PG drop, write a compact record with timestamps and last-known states, then shut down. On restart, merge records and increment a monotonic boot counter. Keep logging firmware idempotent and test under worst-case transients.