Bulk decoupling on a 25 V rail — what the 125 mOhm ESR means
The TPSE686K025S0125: That ESR figure directly sets the ripple current rating and the filter cutoff frequency — for a buck converter switching at 500 kHz, the capacitor's impedance at the switching frequency is dominated by the ESR, not the capacitance, so the output ripple is roughly ESR × inductor ripple current. A lower ESR means less ripple voltage and less self-heating. The 25 V rating gives 1.67× derating on a 15 V rail and 2.5× on a 10 V rail — solid tantalums need that margin because surge current during power-up can spike the voltage across the dielectric. Running this part at 16 V or below keeps the failure rate in the reliable zone per MIL-PRF-55365 guidelines.
Case, footprint, and rework reality
That is a standard low-profile tantalum case; the pad layout matches the generic 2917 land pattern in IPC-7351B. The molded body has a clear polarity band on the anode end — no ambiguity for hand placement or AOI. Rework with a hot-air station at 300°C for 10 seconds per pad is safe — the molded epoxy body does not crack from thermal shock the way conformally coated tantalums sometimes do.
That means it remains in the manufacturer's standard product portfolio and is available through authorized distribution channels. The part is not held in ready inventory at this storefront; each order is placed through the supply channel that best matches the requested quantity and delivery window.