5V fixed rail with 80dB PSRR — what that means for your analog supply
The MCP1755-5002E/MC is a fixed 5V output LDO delivering 300 mA continuous from a 16 V max input rail. The 80 dB PSRR at 1 kHz means ripple from a downstream switching regulator is attenuated by a factor of 10,000 at that frequency — critical for powering analog front-ends, ADC reference buffers, or sensor bias rails where a noisy supply directly degrades SNR.
Dropout and headroom — sizing the input rail
Maximum dropout is 0.5 V at 300 mA load. If the input rail is a 5.0 V switching regulator, the LDO output will fall out of regulation under full load unless the switcher's output is set above 5.5 V with margin for ripple and tolerance. A 6 V or 6.5 V pre-regulator rail gives comfortable headroom.
Temperature range and protection — industrial and automotive ambient
On-chip protection includes over-current, over-temperature, short-circuit, and under-voltage lockout (UVLO) — the UVLO prevents the output from turning on until the input rail is high enough to keep the pass element in regulation.
Package and layout — 8-DFN (2x3) exposed pad
The 8-VFDFN with exposed pad (supplier device package 8-DFN 2x3 mm) requires a thermal via array under the pad to conduct heat to the inner ground plane. The datasheet's recommended land pattern uses a 1.8 x 2.0 mm solder paste aperture on the pad — without adequate thermal vias, the junction temperature rise at 300 mA with 0.5 V dropout (150 mW dissipation) can push the die above 125°C in still air.
Quiescent current and control features — always-on and sequencing
Quiescent current is 100 µA typical, rising to 400 µA max at full load. For battery-backed always-on rails, the 100 µA Iq is low enough to avoid significant drain. The Enable pin allows external sequencing — hold it low until the upstream rail is stable. The Power Good open-drain output asserts when Vout reaches ~92% of nominal, giving a clean reset signal for downstream logic or an MCU.