Monolithic Power Systems Inc. MPM3805GQB-33-Z

Overview

MPM3805GQB-33-Z from Monolithic Power Systems is a fixed-output 3.3V, 0.6A synchronous step-down DC-DC power module with integrated inductor and MOSFETs, housed in a QFN-12 (2.5mm × 3.0mm × 0.9mm) package. It operates from 2.5V–6V input, delivers ±3% output accuracy at 10mA, features Constant-On-Time (COT) control for fast transient response, and includes power-good (PG), enable (EN), and thermal shutdown protection - ideal for space-constrained portable and storage applications.

For engineers reviewing the MPM3805GQB-33-Z datasheet, MPM3805GQB-33-Z pinout, MPM3805GQB-33-Z application, or MPM3805GQB-33-Z equivalent, key selection considerations include its fixed 3.3V output, 17μA quiescent current, 100% duty-cycle dropout capability, open-drain PG with 550kΩ internal pull-up, and integrated 0.47μH inductor enabling minimal external component count (only input/output capacitors required).

Technical Context

The MPM3805GQB-33-Z implements a Constant-On-Time (COT) control architecture with input voltage feed-forward, maintaining switching frequency between 2.8MHz–4.2MHz across input and load conditions. Its internal 0.47μH inductor and matched 110mΩ/70mΩ P/N-FETs enable high-efficiency operation down to light-load DCM via zero-current detection.

It integrates full protection: cycle-by-cycle over-current limiting (1.0A threshold), hiccup-mode short-circuit recovery, thermal shutdown at 150°C (30°C hysteresis), and UVLO with 2.3V turn-on threshold and 300mV hysteresis. The PG pin asserts high when FB voltage is within ±10% of regulation - directly tied to the fixed 3.3V output via internal 0.6V reference.

Key Specifications

Pinout & Package

MPM3805GQB-33-Z uses a thermally enhanced QFN-12 package (2.5mm × 3.0mm × 0.9mm) with exposed thermal pad (pins 3–4 connected to internal SW node and recommended for copper pour connection). Pin 12 (OUT_S) supports remote sensing for improved load regulation in high-current PCB traces.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TSM1053-3.3 and RT6203EGQW, MPM3805GQB-33-Z uniquely combines 3.3V fixed output, 0.6A capability, ultra-low 17μA IQ, integrated inductor, PG with internal pull-up, and OUT_S remote sensing - making it optimal for compact, battery-sensitive, and precision-regulated embedded systems.

Availability

MPM3805GQB-33-Z is available at Aetrix Electronics and suitable for portable instrumentation, SSD/HDD power rails, and space-constrained embedded modules requiring stable component supply, guaranteed long-term sourcing, and RoHS-compliant packaging.

Supply support for MPM3805GQB-33-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 two decades of leadership in DC-DC conversion, motor drivers, and LED lighting controllers.

The MPM3805 product line delivers fully integrated, surface-mount DC-DC modules targeting space- and efficiency-critical applications in portable electronics, storage, and industrial IoT - emphasizing ease of use, minimal external components, and robust thermal performance.

FAQ

What is the maximum allowable input voltage for MPM3805GQB-33-Z?

The absolute maximum input voltage is 6.5V, but the recommended operating range is 2.5V to 6V. Exceeding 6V risks permanent damage to internal MOSFETs and control circuitry, as confirmed by MPS Absolute Maximum Ratings table. Operation above 6V voids warranty and may trigger immediate thermal shutdown.

Does MPM3805GQB-33-Z require external feedback resistors?

No - the -33 suffix denotes a fixed 3.3V output version with internal feedback network. Pin 10 (FB) is internally connected to the 0.6V reference and must remain unconnected; adding external resistors will disrupt regulation and cause output voltage error or instability.

How does the Power Good (PG) pin function on this part?

PG is an open-drain output with internal 550kΩ pull-up to VIN. It asserts high when the regulated output is within ±10% of 3.3V (i.e., 3.0–3.6V); otherwise, it pulls low via internal MOSFET. This provides a reliable power-sequencing signal for MCUs or FPGAs without external pull-up components.

Can MPM3805GQB-33-Z operate in 100% duty cycle mode?

Yes - it supports 100% duty cycle when VIN drops to or below VOUT (3.3V), maintaining regulation without dropout. This is enabled by synchronous rectification and internal gate drive optimization, allowing uninterrupted operation during Li-ion battery discharge from 4.2V down to 3.0V.

What thermal derating applies at 85°C ambient temperature?

With θJA = 65°C/W on a 4-layer PCB, maximum continuous power dissipation at 85°C ambient is (150°C − 85°C) / 65°C/W = 1.0W. At 0.6A and 3.3V output, power dissipation is ~0.2W (assuming 92% efficiency), well within safe margin - no derating needed for typical operation.

Is the exposed thermal pad (pins 3–4) electrically connected?

Yes - pins 3 and 4 are internally connected to the switch node (SW), not ground. They must be soldered to a dedicated copper pour tied to PGND *only* through thermal vias - direct electrical connection to SW would compromise safety and EMC. Refer to MPS layout guide Figure 3 for correct implementation.

What is the minimum off-time specification and why does it matter?

The minimum off-time is 60ns, enforced to prevent inductor current runaway during rapid load transients. This ensures stable COT operation across input/output combinations - for example, at VIN=3.6V and VOUT=3.3V, the calculated off-time is ~24ns, so the 60ns clamp prevents sub-harmonic oscillation and maintains regulation integrity.