The STMicroelectronics ST1L08SPUR is a single-output, positive-adjustable LDO regulator delivering up to 800 mA from a 5.5 V maximum input. The headline number is the 0.09 V maximum dropout at the full 800 mA load — that is 90 mV of headroom needed above the output voltage. For a 3.3 V rail, a 3.4 V input holds regulation through brownout; for a 1.8 V core rail, a 1.89 V supply clears it. The adjustable output range spans 0.5 V to 4 V, set by an external resistor divider, covering the common FPGA core (0.9 V / 1.0 V / 1.2 V), MCU I/O (1.8 V / 2.5 V / 3.3 V), and analog supply voltages without a second regulator variant. Quiescent current sits at 35 µA typical — low enough for always-on domains in battery-powered or standby circuits, while still sourcing the full 800 mA when the load demands it.
80 dB PSRR rolling off to 50 dB at 1 MHz
Power-supply rejection ratio is 80 dB at 100 Hz, degrading to 50 dB at 1 MHz. That 50 dB at 1 MHz is where a 2.2 MHz or 1 MHz switching regulator's fundamental ripple lives — the ST1L08SPUR still attenuates that ripple by a factor of ~316, which is enough to keep a 10 mV p-p switching artifact down to ~30 µV at the output. Below 100 kHz the rejection is better than 70 dB, making this part a clean choice for post-regulating a DC-DC feeding an analog front-end or ADC reference. The PSRR curve is not flat — if your switching frequency sits near 500 kHz to 1 MHz, budget the lower rejection in your noise budget.
Active production, ROHS3, and the control feature set
It is ROHS3 compliant, with no exemptions that complicate EU or California market entry. Control features include an enable pin for sequencing and a power-good open-drain output for reset or PG monitoring; protection covers over-current and over-temperature shutdown.