What the 35 mOhm ESR means for your decoupling budget
The TPSD337K004R0035: The 35 mOhm ESR at 100 kHz is the key figure for a layout engineer sizing the output capacitor bank on a 4 V rail. A 330 µF cap with this ESR gives a self-resonant frequency around 1-2 MHz, where it shunts switching noise from a buck converter before the loop gain runs out. Operating range from -55°C to 125°C covers both cold-start and under-hood ambient without derating the capacitance at high temperature — the tantalum dielectric holds its value across the band.
Single-source risk and the TPS family footprint
The TPSD337K004R0035 is a single-source part from KYOCERA AVX — no direct second-source pin-compatible alternative in the same D case with identical 35 mOhm ESR. For a BOM cost engineer, that flags a single-source risk on a high-volume decoupling position. The ±10% tolerance and 4 V rated voltage are standard for 3.3 V rail bypass, but the 35 mOhm ESR is tighter than many commodity tantalums; a substitution would require re-simulating the ripple current and transient response. If the design can tolerate a slightly higher ESR, the broader TPS family offers other D-case 330 µF parts at 4 V with different impedance profiles — but the order code itself has no listed cross-reference.