Monolithic Power Systems Inc. MP7731DF-LF

Overview

MP7731DF-LF from Monolithic Power Systems is a mono, 5W–30W Class D audio amplifier in TSSOP-20 package with exposed thermal pad, integrating four 180mΩ MOSFETs, analog adaptive modulation (AAM®), and full-bridge output drive for single-supply operation from 9.5V to 18V. It delivers 30W into 4Ω at VDD = 16.5V with 0.1% THD+N at 1W and 90% efficiency at 5W, targeting compact audio systems requiring low pop/click and high PSRR.

For engineers reviewing the MP7731DF-LF datasheet, MP7731DF-LF pinout, MP7731DF-LF application, or MP7731DF-LF equivalent, key selection criteria include its dual-amplifier bridge architecture, integrated bootstrap circuitry (BS1/BS2), thermal shutdown at 150°C, mute/standby control via EN1/EN2, and compatibility with A-weighted noise floor of 370µV in flat-panel display and multimedia computer audio subsystems.

Technical Context

The MP7731DF-LF implements MPS' proprietary Analog Adaptive Modulation (AAM®) topology - a variable-frequency PWM scheme enabling fast transient response, >60dB PSRR at 1kHz, and stable operation without external compensation. Its dual-channel internal structure (Amplifier 1 and Amplifier 2) forms a true bridged-tied-load (BTL) output using SW1 and SW2 pins, each driving one side of the speaker differentially.

It features fully integrated power switches (180mΩ R_DS(on)), on-chip short-circuit protection, thermal shutdown with 30°C hysteresis, and differential input stage with common-mode range from 0V to VDD−1.5V. The device requires external LC filters (e.g., 10µH + 1µF) per channel and bootstrap capacitors (1µF between BS1–SW1 and BS2–SW2) for high-side gate drive.

Key Specifications

Pinout & Package

TSSOP-20 package with exposed thermal pad (MP7731DF variant); RoHS-compliant, halogen-free, lead-free construction; θ_JA = 40°C/W, θ_JC = 6°C/W on 1"² 1oz copper.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar mono Class D audio amplifier applications.

Compared with TAS5707PAP and TPA3110D2PWPR, MP7731DF-LF uniquely combines analog differential input support, integrated short-circuit/thermal protection, and AAM® modulation in a compact TSSOP-20 - making it optimal for analog-source embedded audio where board space, reliability, and design simplicity are prioritized over digital interface flexibility.

Availability

MP7731DF-LF is available at Aetrix Electronics and suitable for flat panel displays, notebook audio subsystems, and smart TV audio modules requiring stable component supply, RoHS/halogen-free compliance, and production-ready thermal performance.

Supply support for MP7731DF-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 and audio applications, headquartered in Kirkland, WA.

The MP7731 belongs to MPS' second-generation integrated Class D audio amplifier product line, engineered specifically for space-constrained consumer electronics needing high-fidelity, high-efficiency mono audio amplification without external gate drivers or protection circuitry.

FAQ

What is the minimum recommended LC filter configuration for MP7731DF-LF?

The typical LC filter uses two identical sections: 10µH shielded inductor (soft saturation core) and 1µF film capacitor per channel. Inductor Q must be 0.7–2.0 to avoid peaking; characteristic frequency should be ~30kHz to pass 20kHz audio while suppressing 400–600kHz switching noise. Ferrite toroids with gapped cores are strongly recommended.

Can MP7731DF-LF operate from a 12V supply and still deliver full 30W output?

No - 30W output requires VDD = 16.5V into 4Ω. At 12V, maximum output is ~17W into 4Ω (per operating specs). For 30W, VDD must be ≥15.5V; absolute max is 18V. Operation above 18V risks permanent damage per absolute maximum ratings.

How are EN1 and EN2 used in system-level control?

EN1 and EN2 must be tied together and driven by the same logic signal. A rising edge >2.0V enables both amplifiers with built-in pop suppression; falling edge <1.2V disables them into <10µA standby. This allows synchronization with system power sequencing or UI mute commands without external logic.

Does MP7731DF-LF require external bootstrap diodes?

No - the MP7731DF-LF integrates all power MOSFETs and bootstrap charging circuitry. Only external 1µF ceramic capacitors between BS1–SW1 and BS2–SW2 are required. No external diodes or charge pumps are needed, simplifying layout and reducing component count.

What is the purpose of separate AGND1/AGND2 and PGND1/PGND2 pins?

AGND1/AGND2 provide quiet reference for analog input stages and bias networks; they must be tied together but kept physically separate from high-current PGND1/PGND2 traces. PGND1/PGND2 carry pulsed switching currents and must connect directly to the exposed thermal pad and bulk capacitor ground to minimize voltage spikes and EMI.

Is MP7731DF-LF compatible with single-ended input sources?

Yes - though optimized for differential inputs, single-ended signals can be applied to PIN1 or PIN2 with NIN1/NIN2 tied to VDD/2 via resistor divider. However, THD+N and PSRR degrade by ~6dB versus differential mode; external AC coupling and level-shifting are required to maintain input common-mode range (0V to VDD−1.5V).