Monolithic Power Systems Inc. MP20045DN-18-LF

Overview

MP20045DN-18-LF from Monolithic Power Systems is a fixed-output 1.8V, 1A low-noise linear regulator with 140mV dropout at full load, 110μA ground current, and 13μVRMS output noise. It uses an internal PMOS pass element and operates from 2.5V to 5.5V input, targeting battery-powered handheld instruments and portable communication devices requiring stable, quiet power rails.

For engineers reviewing the MP20045DN-18-LF datasheet, MP20045DN-18-LF pinout, MP20045DN-18-LF application, or MP20045DN-18-LF equivalent, key selection criteria include dropout voltage under 1A load, PSRR of 56dB at 1kHz, open-drain power-good signaling, thermal shutdown at 150°C, and SOIC8E package compatibility with legacy PCB layouts.

Technical Context

The MP20045DN-18-LF implements a super-low-dropout architecture using an internal PMOS pass transistor, enabling regulation down to 140mV input–output differential at 1A. Its feedback loop references a precise 1.5V internal bandgap, delivering ±2.5% output voltage accuracy across temperature and line/load conditions.

It integrates multiple protection functions: current limiting (1.4–3.0A depending on VIN), thermal shutdown with 20°C hysteresis, and undervoltage lockout with 160mV hysteresis. The EN pin accepts logic-level control (1.5V high threshold), while the open-drain PG pin asserts when VOUT is within 6% of nominal, supporting system power sequencing.

Key Specifications

Pinout & Package

MP20045DN-18-LF is housed in an SOIC8E package (5.0mm × 6.2mm, 1.75mm height) with exposed pad connected to GND for thermal enhancement. Pin 1 is marked by a notch or index area; the exposed pad must be soldered to a PCB ground plane for optimal thermal performance (θJA = 50°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise, 1A LDO applications.

Compared with XC6210B182MR-G and ADP1740ACPZ-1.8-R7, MP20045DN-18-LF uniquely balances ultra-low dropout (140mV), sub-15μVRMS noise, and integrated PG signaling in a compact SOIC8E-making it optimal for space-constrained, battery-sensitive designs where both precision and reliability are non-negotiable.

Availability

MP20045DN-18-LF is available at Aetrix Electronics and suitable for portable medical sensors, industrial handheld scanners, wireless audio transceivers, and smart meter communication modules requiring stable component supply with RoHS-compliant, lead-free packaging.

Supply support for MP20045DN-18-LF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Monolithic Power Systems (MPS) is a fabless semiconductor company specializing in high-performance analog and mixed-signal ICs for power management, motor drive, and automotive applications.

The MP20045 product line targets ultra-low-noise, high-PSRR linear regulation in space-constrained portable electronics-designed specifically to replace older LDOs where battery efficiency, signal integrity, and thermal robustness are critical.

FAQ

What is the minimum input voltage required for MP20045DN-18-LF to maintain regulation?

The MP20045DN-18-LF requires a minimum input voltage of 2.5V to operate, but to sustain 1.8V output at 1A load, VIN must be ≥1.94V (1.8V + 140mV dropout). Its UVLO activates at 2.0V (rising), ensuring reliable startup from fully charged Li-ion cells (≥3.0V) and graceful shutdown near end-of-discharge (≈2.5V).

Can MP20045DN-18-LF be used with ceramic output capacitors smaller than 2.2μF?

No-MP20045DN-18-LF is optimized for 2.2μF ceramic capacitors with ESR <0.9Ω. Using smaller values risks instability, as shown in Figure 2 of the datasheet: ESR must remain within 0.1–100Ω across 0–1A load to ensure phase margin >45°. A 1μF capacitor falls outside this stable region and may cause oscillation or overshoot.

How does the power-good (PG) pin behave during thermal shutdown?

During thermal shutdown, the MP20045DN-18-LF's PG pin remains asserted (high-impedance/open) until VOUT drops below 94% of 1.8V (≈1.7V). Since thermal shutdown preserves output voltage briefly before collapse, PG deasserts only after junction temperature exceeds 150°C *and* output regulation fails-providing accurate fault indication rather than premature warning.

Is the EN pin internally pulled up, and what happens if left unconnected?

The EN pin has no internal pull-up; it features a 550kΩ–1.1MΩ weak pull-down (not pull-up). Leaving EN floating causes undefined behavior due to noise susceptibility. Datasheet explicitly states "Do not float the EN pin." For always-on use, tie EN directly to VIN; for controlled enable, drive with a clean logic signal referenced to GND.

What is the maximum allowable power dissipation in SOIC8E at 70°C ambient?

At TA = 70°C, maximum power dissipation is calculated as PD(MAX) = (TJ(MAX) − TA) / θJA = (125°C − 70°C) / 50°C/W = 1.1W. Exceeding this causes thermal shutdown. With VIN = 5.5V and VOUT = 1.8V, max safe load current is IOUT = PD(MAX) / (VIN − VOUT) ≈ 1.1W / 3.7V ≈ 297mA-confirming full 1A operation requires active cooling or lower VIN.

Does MP20045DN-18-LF support reverse current blocking?

Yes-the internal PMOS pass transistor inherently blocks reverse current flow from VOUT to VIN when the device is disabled or VIN drops below VOUT. This prevents back-powering of upstream supplies and protects battery systems during hot-swap or fault conditions, without requiring external diodes or MOSFETs.