3A fixed 5V LDO with 73dB PSRR floor
The LP3856ES-5.0/NOPB is a single-output positive LDO from Texas Instruments, delivering a fixed 5V rail at up to 3A continuous. The 73dB to 57dB PSRR at 120Hz means this regulator attenuates 120Hz ripple from a rectified mains supply by a factor of roughly 4500 at the low end — critical when the 5V rail feeds an analog front-end or a precision ADC reference. The 0.6V maximum dropout at full load forces the input rail to stay above 5.6V across the load range; below that the output falls out of regulation. The DDPAK/TO-263-5 package (5 leads plus exposed tab) routes the thermal path through the tab to the PCB copper plane — the 3A output at 5V from a 6V input dissipates about 3W, so the board layout must allocate enough copper area to keep the junction below the 125°C absolute maximum. The Enable pin lets a microcontroller or supervisor pull the output to zero without a series pass FET, and the quiescent current sits at 4mA typical. Protection built in covers overcurrent, overtemperature, and short-circuit events — the part folds back current during a fault and recovers automatically when the junction cools.
Active production — no lifecycle risk
ROHS3 compliance is confirmed, so the part ships lead-free and meets the EU RoHS exemption scope. No official second-source or pin-compatible cross-reference exists within the TI portfolio; the DDPAK-5 footprint is specific to this family.
Board-fit and thermal checklist
A 1oz copper pour of at least 1 square inch per watt dissipated keeps the junction temperature in check at 3A load. The Enable pin is active-high; if unused, tie it to the input pin to keep the regulator enabled. Input and output ceramic capacitors should be placed within 5mm of the respective pins to maintain loop stability and transient response.