680 µF at 4 V — the bulk decoupling anchor
The TPSE687M004R0060: That ESR figure is the one that governs ripple handling in a power rail — at 100 kHz, the 60 mOhm limits the self-heating to about 0.4 W at the rated ripple current, which keeps the core temperature rise within the 125°C ceiling.
The capacitance tolerance is ±20% across this range — the actual capacitance at -55°C will be near the low end of the band, but the 60 mOhm ESR stays within the datasheet limit, so the ripple current derating is minimal at cold start. For a 4 V rated part, the derating rule-of-thumb is to apply no more than 50-60% of rated voltage (2.0-2.4 V) in a low-impedance circuit to avoid surge failures. This is standard practice for solid tantalum capacitors — the manufacturer's application notes recommend a 3:1 voltage derating for high-reliability designs.
Sourcing is through independent distribution channels. The part is not single-source for the TPS series — the 680 µF/4 V combination in the E-case is a standard value carried by multiple distributors, so a second-source hedge is straightforward.