3.3 V fixed-output LDO — 100 mA in a 6-bump BGA
The Texas Instruments LM2931IBP-3.3 is a positive fixed-output low-dropout regulator delivering 3.3 V at up to 100 mA from a maximum input of 26 V. It is part of the LM2931 family, designed for automotive and industrial applications where a regulated 3.3 V rail is needed from a battery or unregulated supply. The device integrates over-temperature, reverse polarity, and short-circuit protection, making it suitable for harsh environments where supply faults are expected.
Dropout and PSRR — the real-world margins
Maximum dropout voltage is 0.3 V at the full 100 mA load, meaning the input rail can drop to 3.6 V before the output loses regulation. This is the key spec for battery-powered designs where the supply sags under load. PSRR is 55 dB at 120 Hz, which provides effective ripple rejection from a full-wave rectified supply or a switching pre-regulator. For noise-sensitive analog loads, this keeps the 100/120 Hz ripple off the 3.3 V rail.
Package — 6-VFBGA, 6-uSMD
The LM2931IBP-3.3 is offered in a 6-bump VFBGA (6-VFBGA) package, also designated as 6-uSMD. This is a tiny BGA footprint — the bumps are under the device body, so the PCB fan-out requires fine traces and at least a two-layer board with via-in-pad or microvia capability. The surface-mount assembly profile follows standard lead-free reflow; the package is moisture-sensitive and should be baked per J-STD-020 if exposed beyond the floor life.