Monolithic Power Systems Inc. EVM3805-QB-01A

Overview

EVM3805-QB-01A from Monolithic Power Systems is a dedicated evaluation board for the MPM3805GQB synchronous step-down DC/DC converter, supporting 2.5–6V input and delivering up to 0.6A at fixed 1.2V or adjustable 0.6–3.3V output, with integrated MOSFETs and inductor in a 3.0×2.5×0.9mm QFN package. It demonstrates constant-on-time (COT) control, 17μA quiescent current, and hiccup-mode short-circuit protection.

For engineers reviewing the EVM3805-QB-01A datasheet, EVM3805-QB-01A pinout, EVM3805-QB-01A application, or EVM3805-QB-01A equivalent, this board enables rapid validation of low-voltage, space-constrained power delivery using the MPM3805GQB IC - especially for portable I/O rails, SSD/HDD supplies, and LDO replacement scenarios requiring fast transient response and ultra-low IQ.

Technical Context

The EVM3805-QB-01A implements the MPM3805GQB's COT control architecture, enabling sub-100ns load-step response without external compensation. Its layout integrates all critical high-frequency paths - including VIN decoupling (C1/C3), FB divider (R1/R2), and PG/EN interface - on a compact 6×3.8mm PCB.

It supports both adjustable-output configuration (via R1/R2 feedback network) and fixed-output rework (by swapping U1 to MPM3805GQB-12/-18/-25/-33), with thermal shutdown and cycle-by-cycle over-current protection fully operational in either mode.

Key Specifications

Availability

EVM3805-QB-01A is available at Aetrix Electronics and suitable for portable power validation, SSD/HDD auxiliary rail design, and low-voltage I/O system development requiring stable component supply and rapid functional verification.

Supply support for EVM3805-QB-01A 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 core expertise in DC/DC conversion, motor drivers, and LED lighting controllers.

The MPM3805 product line delivers ultra-compact, high-efficiency buck modules targeting space- and power-constrained applications such as wearables, IoT sensors, and storage subsystems where minimal external components and low IQ are critical.

FAQ

What input voltage range does the EVM3805-QB-01A support?

The board operates from 2.5V to 6V DC input, compatible with single-cell Li-ion batteries (3.0–4.2V), USB 2.0/3.0 ports (5V), and regulated 3.3V/5V system rails. Input must be clean and well-decoupled; ripple exceeding 100mVpp may affect regulation stability.

Can the output voltage be adjusted, and how?

Yes - the default 1.2V output is set by R1=40.2kΩ and R2=40.2kΩ. To adjust, replace R2 with a value calculated as R2 = R1 × (VOUT/0.6 − 1); R1 should remain between 40kΩ and 80kΩ for optimal noise immunity and FB node impedance.

Which MPM3805GQB variants are compatible with this board?

The board is designed for the MPM3805GQB (adjustable version). Fixed-output variants - MPM3805GQB-12 (1.2V), -18 (1.8V), -25 (2.5V), and -33 (3.3V) - can be substituted directly after removing R1/R2 and reworking U1, per the Rev.1.2 Quick Start Guide.

Does the board include power-good signaling?

Yes - the MPM3805GQB's PG (power good) pin is routed to test point TP2. When VOUT reaches 90% of target and remains stable for >1ms, PG asserts high (open-drain, pulled up to VIN via onboard 100kΩ). This signal supports sequencing in multi-rail systems.

What thermal performance can be expected during 0.6A operation?

At 6V input and 1.2V/0.6A output, the board reaches ~65°C case temperature after 5 minutes at 25°C ambient with no airflow. The MPM3805GQB's thermal shutdown activates above 150°C junction, providing robust fault tolerance under sustained overload.

Is the PCB layout optimized for EMI reduction?

Yes - the Rev.1.2 layout minimizes high di/dt loops: input capacitor (C1) is placed adjacent to VIN and GND pins of U1; power inductor is integrated into the IC; and FB trace is kept short and远离 switching nodes. Ground plane is solid on bottom layer with thermal vias under U1.