Monolithic Power Systems Inc. MP7731DF-LF-P

Overview

MP7731DF-LF-P from Monolithic Power Systems is a mono, 5W–30W Class D audio amplifier in TSSOP-20EP package with integrated 180mΩ full-bridge MOSFETs, Analog Adaptive Modulation (AAM®) topology, and built-in click/pop suppression. It delivers 30W into 4Ω at 16.5V supply, achieves 90% efficiency at 5W output, and supports 9.5V–18V operation for flat-panel displays and multimedia computers.

For engineers reviewing the MP7731DF-LF-P datasheet, MP7731DF-LF-P pinout, MP7731DF-LF-P application, or MP7731DF-LF-P equivalent, this device is selected for high-efficiency mono bridged audio amplification where THD+N ≤ 0.2%, PSRR ≥ 60dB, thermal shutdown at 150°C, and dual-channel bootstrap-driven switching are required.

Technical Context

The MP7731DF-LF-P implements MPS' proprietary variable-frequency Analog Adaptive Modulation (AAM®) topology to achieve fast transient response, excellent power supply rejection (60dB at 1kHz), and low-noise operation without external compensation. Its dual full-bridge architecture uses two independent 180mΩ switch pairs (SW1/PGND1/VDD1/BS1 and SW2/PGND2/VDD2/BS2) driven by internal gate drivers.

It integrates differential input stages (PIN1/NIN1 and PIN2/NIN2), dual enable inputs (EN1/EN2), analog grounds (AGND1/AGND2), and power grounds (PGND1/PGND2) with strict isolation requirements. Thermal shutdown (150°C trip, 30°C hysteresis) and short-circuit protection operate autonomously without external circuitry.

Key Specifications

Pinout & Package

TSSOP-20EP (exposed paddle) package with 0.65mm pitch, JEDEC MO-153 compliant; thermal pad soldered to PCB for θJC = 6°C/W and θJA = 40°C/W performance.

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 MAX9719ETE+, MP7731DF-LF-P offers superior integration (no external bootstrap diodes), higher efficiency at low power, and hardware-based click/pop elimination-making it optimal for display OEMs prioritizing reliability and layout simplicity over digital configurability.

Availability

MP7731DF-LF-P is available at Aetrix Electronics and suitable for flat panel displays, notebook computers, and smart TVs requiring stable component supply, RoHS-compliant packaging, and long-term industrial availability.

Supply support for MP7731DF-LF-P 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.

The MP7731 belongs to MPS' second-generation fully integrated Class D audio amplifier product line, engineered specifically for space-constrained consumer displays and computing devices needing high-efficiency, low-THD mono amplification without external power switches.

FAQ

What is the minimum recommended LC filter cutoff frequency for MP7731DF-LF-P?

The LC filter characteristic frequency should be set between 20kHz and 35kHz to pass full audio bandwidth while attenuating switching harmonics. For a 4Ω load, typical values are 10μH inductors and 100nF film capacitors, yielding f₀ ≈ 25kHz and Q ≈ 1.2-within the recommended 0.7–2.0 range for flat passband response and low peaking.

Can MP7731DF-LF-P drive an 8Ω speaker, and what is the expected output power?

Yes-it delivers 17W into 8Ω at VDD=16.5V and THD+N=10%, per operating specifications. Efficiency improves to 88% at 10W output due to lower conduction losses, and THD+N drops to 0.1%. No circuit changes are needed beyond adjusting LC filter values for optimal damping at the higher impedance.

How does the Analog Adaptive Modulation (AAM®) topology improve PSRR versus fixed-frequency Class D amplifiers?

AAM® dynamically adjusts switching frequency in response to supply voltage and load conditions, maintaining constant energy per cycle and minimizing coupling of supply ripple into the audio band. This yields 60dB PSRR at 1kHz-15dB higher than comparable fixed-frequency devices-without requiring external supply filtering or feedback compensation.

What is the purpose of tying EN1 and EN2 together, and what happens if they are driven independently?

EN1 and EN2 are internally bonded to control both amplifier channels simultaneously; driving them separately violates the functional specification and may cause asymmetric switching, increased THD+N, or latch-up. The datasheet mandates connection to a single enable source-either microcontroller GPIO or system power-good signal-with rise/fall thresholds of 1.4V/0.4V respectively.

Is the exposed thermal pad on the TSSOP-20EP package electrically connected, and how should it be handled in PCB layout?

No-the exposed paddle is electrically isolated and serves only for thermal conduction. It must be soldered to a large copper pour connected to PGND1/PGND2 via multiple thermal vias (≥6×0.3mm) to achieve θJC = 6°C/W. Floating or unconnected pads increase junction temperature by >25°C at full 30W output, risking thermal shutdown.

Does MP7731DF-LF-P support DC-coupled inputs, or is AC coupling mandatory?

AC coupling is mandatory. The input common-mode range is 0V to VDD−1.5V, and the internal bias sets the differential input stage at VDD/2. Direct DC coupling would violate the absolute maximum rating for VPIN/VNIN (−1V to VDD+1V) and cause saturation or damage. C7/C12 input coupling capacitors (e.g., 1μF X7R) are required per the typical application circuit.

What is the maximum allowable voltage on BS1 and BS2 pins relative to their respective SW pins?

BS1 and BS2 voltages must remain within VSW−0.3V to VSW+6.5V per absolute maximum ratings. Exceeding this range risks gate oxide breakdown in the internal high-side MOSFETs. A 1μF ceramic capacitor placed directly between BS1–SW1 and BS2–SW2 ensures proper bootstrap voltage generation and prevents undershoot during dead-time transitions.