Monolithic Power Systems Inc. MP7731DF-LF-Z

Overview

MP7731DF-LF-Z 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 pop/click suppression. It delivers 30W into 4Ω at 16.5V supply with 90% efficiency at 5W output and <0.1% THD+N at 1W/1kHz-used in flat-panel displays and multimedia computers for compact, high-fidelity speaker drive.

For engineers reviewing the MP7731DF-LF-Z datasheet, MP7731DF-LF-Z pinout, MP7731DF-LF-Z application, or MP7731DF-LF-Z equivalent, key selection criteria include its dual-channel differential input architecture, 9.5V–18V operating range, integrated thermal shutdown, 400–600kHz idle switching frequency, and exposed-pad thermal performance (θJC = 6°C/W).

Technical Context

The MP7731 employs MPS's proprietary variable-frequency Analog Adaptive Modulation (AAM®) topology to achieve >60dB PSRR at 1kHz and fast transient response without external compensation. Its full-bridge output stage uses four integrated 180mΩ MOSFETs per channel, driven by bootstrap circuits (BS1/BS2) supporting high-side gate biasing up to VSW+6.5V.

It operates as a single-supply bridged-tied-load (BTL) amplifier with dual differential inputs (PIN1/NIN1 and PIN2/NIN2), independent power domains (VDD1/VDD2, PGND1/PGND2), and separate analog grounds (AGND1/AGND2) to minimize crosstalk. Mute/standby control is implemented via dual EN1/EN2 pins tied together.

Key Specifications

Pinout & Package

TSSOP-20EP (exposed paddle) package with 0.65mm pitch, 4.4mm × 6.6mm body, and thermal pad optimized for θJA = 40°C/W on 1"² 1oz copper. Exposed paddle must be soldered to PCB ground plane for thermal and electrical integrity.

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-Z uniquely combines analog differential inputs, integrated pop suppression, and AAM® modulation-making it optimal for analog-source consumer displays where simplicity, acoustic quality, and rapid time-to-market are critical.

Availability

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

Supply support for MP7731DF-LF-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 mixed-signal ICs for power management and audio applications, headquartered in Kirkland, WA.

The MP7731 belongs to MPS's second-generation Class D audio amplifier product line, engineered specifically for space-constrained consumer electronics requiring high efficiency, low THD+N, and minimal external components.

FAQ

What is the minimum recommended LC filter corner frequency for MP7731DF-LF-Z?

The LC filter characteristic frequency should be set between 30kHz and 50kHz to pass full 20Hz–20kHz audio bandwidth while attenuating 400–600kHz switching harmonics. Use L = 10µH and C = 1µF per side for 4Ω loads, ensuring Q remains between 0.7 and 2.0 to avoid peaking or excessive ripple.

Can MP7731DF-LF-Z operate from a 9V supply?

Yes-MP7731DF-LF-Z supports 9.5V minimum supply voltage. At 9.5V, maximum output power drops to ~12W into 4Ω (THD+N ≤10%), with efficiency falling to ~82%. Ensure input coupling capacitors and gain-setting resistors are recalculated to maintain proper common-mode bias at reduced VDD/2.

How is thermal performance affected if the exposed paddle is not soldered?

Without soldering the exposed paddle to a thermal pad, θJA degrades from 40°C/W to >75°C/W, causing junction temperature to exceed 150°C at >15W output. This triggers thermal shutdown and risks permanent damage. Reflow profile must ensure full paddle wetting with ≥90% solder coverage.

Does MP7731DF-LF-Z support single-ended input configuration?

No-it requires differential input signals on PIN1/NIN1 and PIN2/NIN2. Single-ended sources must be converted using an external op-amp or transformer to maintain common-mode rejection and avoid increased THD+N. The internal input stage has no provision for ground-referenced inputs.

What is the purpose of tying EN1 and EN2 together?

EN1 and EN2 control separate internal amplifier sections but share a common enable logic threshold. Tying them ensures simultaneous activation/deactivation of both half-bridges, preventing shoot-through current or unbalanced output states that could damage the speaker or IC during transition.

Is the MP7731DF-LF-Z pin-compatible with earlier MP7730 variants?

No-MP7731DF-LF-Z uses a 20-pin TSSOP-EP package with distinct pin mapping (e.g., dual VDD/PGND pairs, separate BS pins). MP7730 uses 16-pin QFN and lacks independent power domains. PCB layout, decoupling, and LC filter placement are not interchangeable.