Monolithic Power Systems Inc. MP2126DN-LF-Z

Overview

MP2126DN-LF-Z from Monolithic Power Systems is a dual-output power management IC integrating a 2.5A synchronous step-down switcher (1.25MHz, 0.6V–6V output) and a standalone 0.5A low-dropout linear regulator (LDO), both regulated to as low as 0.6V. It operates from 2.5V–6V on IN1 and 1V–VIN1 on IN2, features cycle-by-cycle current limiting, thermal shutdown, and 1µA shutdown current - designed for single-cell Li+-powered portable electronics including DVD±RW drives and LCD TVs.

For engineers reviewing the MP2126DN-LF-Z datasheet, MP2126DN-LF-Z pinout, MP2126DN-LF-Z application, or MP2126DN-LF-Z equivalent, key selection criteria include dual-channel regulation capability, SOIC8E package with exposed pad for thermal management, 1.25MHz fixed-frequency current-mode control, LDO noise isolation via separate IN2 input, and compatibility with ceramic output capacitors for compact, high-efficiency designs.

Technical Context

The MP2126 employs peak current-mode PWM control with internal slope compensation, enabling stable operation at duty cycles >50% and fast transient response. Its integrated high-side PFET (0.20Ω) and synchronous NFET rectifier (0.15Ω) eliminate external diodes and support up to 90% efficiency at 2.5A load.

The standalone LDO uses IN2 as dedicated input for noise-sensitive circuitry, drawing bias from IN1 while allowing independent voltage sourcing - e.g., connecting IN2 to the switcher output reduces power dissipation and improves PSRR by isolating switching noise from the LDO path.

Key Specifications

Pinout & Package

MP2126DN-LF-Z is housed in an 8-pin SOIC package with exposed thermal pad (SOIC8E), optimized for thermal dissipation (θ_JA = 50°C/W) in space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-output power management applications.

Compared with TPS65023RSBR and RT8059ZSP, MP2126DN-LF-Z uniquely combines 2.5A buck current, true 100% duty-cycle operation for extended battery runtime, and isolated LDO input (IN2) - making it optimal for portable systems demanding high current, low-noise analog rails, and deep-discharge resilience.

Availability

MP2126DN-LF-Z is available at Aetrix Electronics and suitable for DVD±RW drives, LCD TVs, industrial handheld meters, and portable medical sensor modules requiring stable component supply across production lifecycles.

Supply support for MP2126DN-LF-Z 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 power ICs, with over 20 years of expertise in DC-DC conversion and power management solutions.

The MP2126 belongs to MPS's integrated power SoC product line, engineered specifically for space- and efficiency-constrained portable electronics that require dual regulated outputs with minimal external components and robust battery discharge support.

FAQ

What is the minimum input voltage required for the MP2126DN-LF-Z to regulate both outputs?

The MP2126DN-LF-Z requires a minimum 2.5V on IN1 to operate the switcher and bias the LDO control circuitry. The LDO's IN2 input must be at least 1V and no less than its output voltage plus dropout (e.g., 1.2V output needs ≥1.45V on IN2). Below 2.5V on IN1, the device enters undervoltage lockout and disables both regulators.

Can the LDO output be set independently of the switcher output voltage?

Yes. The MP2126DN-LF-Z uses separate feedback pins (FB1 and FB2) with identical 0.596V reference voltages, allowing independent resistor-divider programming of VOUT1 (switcher) and VOUT2 (LDO) from 0.6V to 6V. For example, VOUT1 can be set to 1.8V for a processor core while VOUT2 is set to 3.3V for I/O peripherals.

How does the MP2126DN-LF-Z handle short-circuit conditions on the LDO output?

Under LDO output short-circuit, the MP2126 limits current to 625–725mA (typical) and maintains regulation until thermal shutdown activates at 150°C. Unlike the switcher, the LDO lacks active foldback or frequency reduction - its protection relies on current limit and thermal shutdown, requiring external fuse or current-limiting resistor for sustained fault tolerance.

Is the exposed pad on the SOIC8E package electrically connected, and how should it be handled in PCB layout?

Yes, the exposed pad is internally connected to GND and must be soldered to a solid copper thermal pad on the PCB. It serves as the primary thermal and electrical ground return for both switcher and LDO. Layout best practice requires ≥4 thermal vias (0.3mm diameter) connecting the pad to inner-layer ground planes to achieve the specified θ_JA = 50°C/W.

Does the MP2126DN-LF-Z support forced PWM mode, or is it strictly constant-frequency current-mode?

The MP2126DN-LF-Z operates exclusively in fixed-frequency (1.25MHz) peak current-mode control with internal slope compensation. It does not support forced PWM, skip-mode, or burst-mode operation - ensuring consistent EMI profile and predictable transient response, but with higher light-load quiescent current (350–500µA) compared to adaptive-mode ICs.

What is the maximum recommended inductor DCR for achieving 90% efficiency at 2.5A load?

To achieve ≥90% efficiency at 2.5A, the inductor DCR must be ≤100mΩ, as specified in the datasheet. Higher DCR increases I²R losses - for example, a 150mΩ inductor would reduce efficiency to ~87% at 2.5A due to 0.94W conduction loss versus 0.63W with 100mΩ.

Can the EN pin be used to sequence the switcher and LDO turn-on independently?

No. The EN pin enables or disables both the switcher and LDO simultaneously - there is no internal sequencing or independent control. To achieve power-up sequencing, external circuitry (e.g., RC delay on EN or dedicated sequencer IC) must be added to stagger activation of upstream supplies feeding IN1 and IN2.