SC-70-5 LDO for noise-sensitive 1.8 V rails
The MAX8511EXK18 is a single-output, fixed 1.8 V LDO from Analog Devices, rated for 120 mA continuous output. The PSRR profile — 72 dB at 1 kHz, rolling off to 46 dB at 100 kHz — is the headline spec for anyone feeding a sensitive analog load. A 1.8 V ADC reference or a PLL supply sees the 1 kHz ripple from a switching preregulator attenuated by 72 dB; at 100 kHz the attenuation drops to 46 dB, so the upstream converter's switching frequency should stay below 100 kHz or the output cap needs a low-ESR ceramic to handle the residual ripple.
90 µA quiescent — always-on and battery duty
Quiescent current is 90 µA typical, drawn regardless of load. In an always-on sensor node or a micro that sleeps at 10 µA, the LDO's own consumption dominates the idle budget — the trade-off is the PSRR and the 120 mA headroom for brief transmit bursts. The shutdown pin (active-low) pulls Iq to near zero when the load is powered down, so a GPIO-controlled enable can cut the 90 µA during long sleep intervals. The 90 µA figure is typical at 25°C; expect it to rise with temperature, but the datasheet's maximum at 85°C is still within the budget for most battery-powered designs.