68 µF bulk decoupling for 20 V rails
The TPSD686M020R0200: This part sits in the TPS series, KYOCERA AVX's general-purpose industrial-grade molded tantalum line.
ESR and temperature — the real selection axes
The 200 mΩ ESR governs how much AC ripple this cap can absorb before the internal temperature rise exceeds the 125°C absolute max. For a 20 V rail switching at 500 kHz, the ripple current rating is roughly 1.2 A RMS — above that, the ESR losses push the core temperature past the derating curve. The -55°C to 125°C operating range covers industrial motor drives and automotive underhood electronics, but at the low end the ESR roughly doubles, so the ripple current budget shrinks. The ±20% tolerance is standard for tantalum electrolytics — this is a bulk storage cap, not a timing or filter element. At 68 µF, the actual capacitance at 20 V bias is about 20% lower than the nominal value due to DC bias derating, so the effective decoupling capacitance is closer to 54 µF. The D case is the most common footprint for this capacitance-voltage combination, meaning the PCB land pattern is widely supported across manufacturers.
Active production — no LTB pressure
For a BOM that already qualifies this cap, the supply chain risk is low — no forced redesign or end-of-life inventory hoarding.