Fixed 2.8V LDO in a 4-DSBGA footprint
The LP5990TMX-2.8/NOPB is a single-output positive LDO from Texas Instruments, delivering a fixed 2.8V at up to 200mA from a maximum input of 5.5V. The 4-DSBGA package (0.8mm pitch typical) keeps the footprint under 2mm², suiting it for space-constrained portable or wireless designs where a clean, regulated rail is needed for analog or RF blocks.
PSRR and quiescent current — the battery-life tradeoff
PSRR is 55dB at 10kHz — this is the mid-band rejection figure that matters for switching-regulator ripple at typical converter frequencies. Below 1kHz the PSRR is higher; above 100kHz it rolls off, so input-side filtering ahead of the LDO is still needed if the upstream switcher runs at 2MHz or above. Quiescent current is 75µA typical — not the lowest in class, but low enough that the regulator's own draw does not dominate the battery budget in a sensor node that spends most of its time in a low-power sleep state. The enable pin lets the system controller cut the LDO's bias entirely when the rail is not needed.
Dropout headroom and protection suite
With a 3.3V rail, that leaves 250mV of margin; with a 3.0V rail, the margin is only 50mV, which is tight over temperature and tolerance. Built-in protection covers over-current, over-temperature, and short-circuit events. These are self-recovering — the LDO shuts down and re-starts when the fault clears, which avoids latch-up in a portable device that gets dropped or sees a momentary output short.
Temperature grade and board integration
The 4-DSBGA package has no exposed thermal pad; heat is conducted through the solder balls and PCB copper plane. A 2-layer board with a solid ground pour under the package is adequate for 200mA continuous at 85°C, but a 4-layer board with a dedicated thermal via array under the die area improves junction-to-ambient resistance by roughly 20%. Mounting is surface-mount only. The DSBGA package requires a solder-paste stencil with aperture matching the 0.4mm ball pitch — standard reflow profile per JEDEC J-STD-020 works. The package is moisture-sensitive; bake before reflow if the floor life has been exceeded.