Monolithic Power Systems Inc. MP7745DF-LF-P

Overview

MP7745DF-LF-P from Monolithic Power Systems is a stereo Class D audio amplifier delivering 2 × 20W into 4Ω loads at 24V supply, integrating dual 250mΩ N-channel power MOSFETs, startup/shutdown pop elimination, and thermal/short-circuit protection. It operates from a single 9.5–26V supply and targets flat-panel TV and home stereo systems requiring high-efficiency, low-THD amplification.

For engineers reviewing the MP7745DF-LF-P datasheet, MP7745DF-LF-P pinout, MP7745DF-LF-P application, or MP7745DF-LF-P equivalent, key selection criteria include its 93% efficiency at 20W/4Ω, 0.05% THD+N at 1W/8Ω, 1MHz max switching frequency, integrated bootstrap circuitry, and TSSOP20-Exposed package thermal performance.

Technical Context

The MP7745DF-LF-P implements MPS's proprietary Analog Adaptive Modulation™ topology with variable-frequency control, enabling fast transient response and excellent linearity without external compensation. Its differential input stage accepts signals referenced to VDD/2 via internal resistive dividers at REF1/REF2, supporting gain setting via external RIN/RFB networks.

Each channel uses a single-ended output stage with integrated high-side and low-side 250mΩ N-MOSFETs driven by bootstrap circuits (BS1/SW1 and BS2/SW2), requiring external 0.1–1µF bootstrap capacitors. Short-circuit protection monitors both MOSFET currents and triggers automatic restart after fault clearance, while thermal shutdown activates at 150°C with 30°C hysteresis.

Key Specifications

Pinout & Package

TSSOP20-Exposed Pad package with 0.65mm pitch; exposed thermal pad must be soldered to PCB ground plane for θJC = 6°C/W and reliable 20W/channel operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP7742DF-LF-P, the MP7745DF-LF-P delivers double output power with identical footprint and protection features; versus TAS5722LRTVR, it eliminates digital interface dependencies and simplifies analog-centric designs but lacks programmable audio processing.

Availability

MP7745DF-LF-P is available at Aetrix Electronics and suitable for flat panel TV, portable docking station, and home stereo systems requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP7745DF-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 over 20 years of expertise in DC/DC conversion, LED drivers, and audio amplifiers.

The MP7745 belongs to MPS's Class D Audio Amplifier product line, engineered specifically for high-efficiency, low-EMI stereo amplification in space- and thermally constrained consumer electronics.

FAQ

What is the minimum recommended LC filter configuration for MP7745DF-LF-P?

The datasheet specifies 10µH inductors and 0.47µF film capacitors as the baseline LC filter for 24V operation. Inductor saturation current must exceed 5.5A peak, and capacitor ripple current rating should support ≥3.5A RMS. Q-factor must be maintained between 0.7–1.0 using speaker impedance to prevent passband peaking or excessive noise.

Can MP7745DF-LF-P drive 8Ω speakers at full rated power?

No - maximum output is 11W per channel into 8Ω at 10% THD+N and 24V supply. The device is optimized for 4Ω loads; attempting 20W into 8Ω exceeds safe operating area and risks thermal shutdown due to increased conduction losses and reduced efficiency.

Is an external Schottky diode required for normal operation?

Only if short-circuit protection is needed. The datasheet mandates two B340-type Schottky diodes (cathode to SW, anode to PGND) for overload protection. If the application has controlled load environments and no risk of speaker wire shorts, these diodes may be omitted to reduce BOM cost and board area.

How does the bootstrap circuit function without external high-voltage charge pumps?

The MP7745DF-LF-P integrates internal charge-pump circuitry that charges the external bootstrap capacitor (CBS1/CBS2) from VDD during low-side MOSFET conduction. This generates a gate-drive voltage ~VDD above SW node potential, enabling full enhancement of the high-side N-MOSFET without external components.

What is the purpose of separate AGND and PGND pins?

AGND pins (4,5,9) carry low-level analog reference and input currents, while PGND pins (15,20) handle high-current switching return paths. Separating these grounds prevents voltage spikes on PGND from modulating the analog bias points, which would increase THD+N and noise floor by up to 12dB.

Does MP7745DF-LF-P support I²C or digital control interfaces?

No - it is an analog-input-only amplifier with no digital communication capability. All configuration (gain, switching frequency, protection thresholds) is performed via external passive components. For digitally configurable audio amps, consider MPS's MP7749 or TI's TAS57xx series.

What is the maximum allowable PCB temperature rise under 20W/channel continuous operation?

With the exposed pad soldered to a 4-layer PCB having ≥4 cm² copper pour, junction-to-ambient thermal resistance is 40°C/W. At 20W/channel (40W total), ΔTJA = 40W × 40°C/W = 1600°C - physically impossible. Real-world derating requires ≤12W/channel continuous or active airflow to maintain TJ < 125°C per JEDEC guidelines.