Monolithic Power Systems Inc. MPM3805GQB-18-Z

Overview

MPM3805GQB-18-Z from Monolithic Power Systems is a synchronous step-down DC-DC power module with integrated inductor, delivering 1.8 V fixed output at up to 0.6 A from 2.5–6 V input. It uses Constant-On-Time (COT) control for fast transient response, features ultra-low 17 μA quiescent current, and includes power-good (PG) and enable (EN) pins for sequencing in space-constrained portable systems.

For engineers reviewing the MPM3805GQB-18-Z datasheet, MPM3805GQB-18-Z pinout, MPM3805GQB-18-Z application, or MPM3805GQB-18-Z equivalent, this module supports compact, low-noise, high-efficiency point-of-load regulation in FPGA I/O rails, SSD power domains, and battery-powered instrumentation where board area and thermal performance are critical.

Technical Context

The MPM3805GQB-18-Z integrates a 110 mΩ P-channel and 70 mΩ N-channel MOSFET pair with a 0.47 µH shielded inductor in a monolithic QFN-12 package. Its COT architecture uses input-voltage feedforward to maintain switching frequency stability across 2.5–6 V input and 1.8 V output, achieving 2.8–4.2 MHz operation with 60 ns minimum off-time.

It implements cycle-by-cycle over-current protection with ≥1 A current limit, hiccup-mode short-circuit recovery, thermal shutdown at 150 °C (30 °C hysteresis), and precise ±1.5% output regulation (1.755–1.845 V at 10 mA, 25 °C). The PG pin provides open-drain status with ±10% window and 50 µs delay relative to FB voltage deviation.

Key Specifications

Pinout & Package

MPM3805GQB-18-Z is housed in a thermally enhanced QFN-12 package (2.5 mm × 3.0 mm × 0.9 mm) with exposed thermal pad (pins 3–4 connected internally to SW node and tied to copper pour for heat dissipation).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output synchronous buck module applications.

Compared with TPS826718 and LTM4622IY#PBF, the MPM3805GQB-18-Z uniquely balances ultra-small size, sequencing-enabling PG/EN pins, and ultra-low IQ in a single 1.8 V rail - making it optimal for portable, battery-sensitive, and space-constrained single-rail designs.

Availability

MPM3805GQB-18-Z is available at Aetrix Electronics and suitable for portable instrumentation, FPGA I/O power, and SSD controller applications requiring stable component supply, consistent parametric performance, and long-term production continuity.

Supply support for MPM3805GQB-18-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 design centers in the US, China, and Taiwan, and global manufacturing partnerships.

The MPM3805 series targets space-constrained, low-power embedded systems needing fully integrated, easy-to-deploy DC-DC solutions - emphasizing minimal external components, thermal robustness, and seamless integration into portable and industrial platforms.

FAQ

What is the absolute maximum input voltage rating for MPM3805GQB-18-Z?

The absolute maximum VIN is 6.5 V per the datasheet's Absolute Maximum Ratings table. Exceeding this may cause permanent damage. The recommended operating range remains 2.5 V to 6 V, and the under-voltage lockout (UVLO) rising threshold is 2.15–2.48 V, ensuring reliable startup across battery discharge profiles.

Does MPM3805GQB-18-Z require external feedback resistors?

No. The "-18" suffix denotes a factory-trimmed fixed 1.8 V output; the FB pin is internally connected and marked NC (no connect) in the pinout. Only input and output ceramic capacitors are required - eliminating resistor selection, placement, and tolerance errors in production.

How does the OUT_S pin improve regulation accuracy?

OUT_S provides remote voltage sensing by connecting directly to the load side of the output capacitor or load terminals. This compensates for IR drop across PCB traces and connectors, maintaining ±1.5% output accuracy at the load rather than just at the module pins - critical for high-current or long-trace applications.

What thermal management practices are recommended for continuous 0.6 A operation?

For full 0.6 A load at elevated ambient temperatures, solder the exposed thermal pad (pins 3–4) to a ≥100 mm² internal or bottom-layer copper pour with ≥4 thermal vias (0.3 mm diameter) to inner/ground planes. The θJA is 65 °C/W on a 4-layer JEDEC board; derate output current above 85 °C ambient per the thermal shutdown hysteresis curve.

Can MPM3805GQB-18-Z operate in 100% duty cycle mode, and what is its practical benefit?

Yes - the device supports 100% duty cycle operation when VIN ≤ VOUT + dropout loss (typically <100 mV at light load). This enables uninterrupted regulation during input brownouts (e.g., Li-ion dropping from 3.2 V to 1.8 V), eliminating the need for a backup LDO and simplifying power architecture in battery-critical systems.

Is the PG (Power Good) signal actively driven or open-drain, and how should it be interfaced?

PG is an open-drain output with a 550 kΩ internal pull-up to VIN. It asserts high (≈VIN) when FB voltage is within ±10% of 1.8 V and pulls low (<0.4 V at 1 mA sink) otherwise. Interface directly to MCU GPIO with internal or external pull-up; no level-shifting needed for 3.3 V or 5 V logic systems.

What is the minimum off-time specification, and why does it matter for light-load efficiency?

The minimum off-time is 60 ns. This prevents sub-harmonic oscillation and ensures stable discontinuous conduction mode (DCM) operation at light loads. By forcing a minimum dead time, the controller avoids erratic switching and enables zero-current detection - improving light-load efficiency without compromising stability.