What this LDO brings to the rail
The STMicroelectronics LD29150DT25R is a single-output, fixed 2.5V LDO regulator rated for 1.5A continuous output. It comes in a TO-252-3 DPAK surface-mount package with an exposed tab for thermal dissipation.
Dropout and headroom — the 0.7V max at full load
Maximum dropout voltage is 0.7V at 1.5A load. That means a 3.3V input rail still holds the 2.5V output in regulation during a cold-crank or brownout condition where the input sags. For a 5V nominal input, the headroom is generous, but the designer should check the minimum input voltage at the worst-case load and temperature when sizing the pre-regulator or bulk capacitor.
The 70 dB power-supply rejection ratio at 120 Hz is the figure that matters when this LDO feeds an analog front-end or ADC reference. It attenuates the 100/120 Hz ripple from a mains-rectified bulk supply by a factor of about 3160. For a 100 mVpp ripple on the input, the output sees roughly 32 µVpp — clean enough for 12-bit systems without a post-filter. The PSRR rolls off at higher frequencies, so a 1 µF to 4.7 µF ceramic on the output helps maintain rejection above 10 kHz.
DPAK package — thermal and mounting notes
The TO-252-3 DPAK has two leads plus the tab. The tab is the ground connection and the primary heat path. For 1.5A output with a 1V dropout, dissipation is 1.5W; without a copper pour or via stitch on the tab pad, the junction temperature climbs above 125°C at 85°C ambient.
Protection features and quiescent draw
Over-current and over-temperature protection are built in. The quiescent current is 180 µA typical, which is moderate for a 1.5A LDO — not the lowest-Iq choice for battery gear, but acceptable for always-on rails in line-powered equipment. The maximum supply current is 80 mA, which covers the drive stage at full load.
No single-supplier exposure — the DPAK footprint is standard across multiple LDO families if a second source is needed.