LM4861 Bridge-Connected Audio Power Amplifier

Overview

The LM4861 is a high-performance bridge-connected audio power amplifier designed to deliver superior audio quality with minimal external components. This amplifier is part of the Boomer® audio power amplifier series, which is specifically engineered for compact, surface-mount applications requiring high-quality audio output. The LM4861 is capable of delivering 1.1W of continuous average power into an 8Ω load with less than 1% Total Harmonic Distortion (THD) when operating from a 5V power supply.

One of the standout features of the LM4861 is its elimination of the need for output coupling capacitors, bootstrap capacitors, or snubber networks, making it an optimal choice for space-constrained designs. Additionally, the amplifier includes an externally controlled low-power consumption shutdown mode and internal thermal protection, enhancing its reliability and energy efficiency.

Features

• High Output Power: Delivers 1.1W continuous average power into an 8Ω load at 1% THD with a 5V supply.
• Bridge-Tied Load (BTL) Configuration: Eliminates the need for output coupling capacitors, reducing component count and board space.
• Low External Component Count: No bootstrap capacitors or snubber networks required.
• Low Power Consumption: Features a shutdown mode for power-saving operation.
• Thermal Protection: Built-in thermal shutdown mechanism prevents overheating.
• Surface-Mount Packaging: Optimized for modern PCB designs and compact applications.
• Wide Supply Voltage Range: Operates efficiently across a range of supply voltages.
• High Signal-to-Noise Ratio (SNR): Ensures clear and high-fidelity audio output.

Applications

The LM4861 is versatile and suitable for a wide range of audio applications, including but not limited to:

• Portable electronic devices (e.g., smartphones, tablets, MP3 players)
• Desktop and laptop computers
• Gaming consoles and handheld gaming devices
• Personal audio accessories (e.g., headphones, Bluetooth speakers)
• Multimedia systems and home entertainment devices
• Automotive infotainment systems (where applicable)
• Industrial audio equipment and intercom systems

Electrical Characteristics

The following table summarizes the key electrical specifications of the LM4861 under typical operating conditions (V_DD = 5V, T_A = 25°C, unless otherwise noted):

Absolute Maximum Ratings

• Supply Voltage (V_DD): 6V
• Output Power (P_OUT): 1.1W (continuous, 8Ω load)
• Operating Temperature Range: -40°C to +85°C
• Storage Temperature Range: -65°C to +150°C

Typical Performance Characteristics

• Total Harmonic Distortion + Noise (THD+N): <1% at 1.1W, 8Ω, 1kHz
• Quiescent Current (I_Q): 4mA (typical)
• Shutdown Current (I_SD): 0.1µA (typical)
• Power Supply Rejection Ratio (PSRR): 60dB (typical)
• Signal-to-Noise Ratio (SNR): 90dB (typical)
• Gain Bandwidth Product: 1MHz (typical)

Package Information

The LM4861 is available in a compact surface-mount package, ensuring ease of integration into modern PCB designs. The following are the key package details:

Package Type

• MSOP-8 (Micro Small Outline Package): This package is designed for space-constrained applications and offers excellent thermal and electrical performance.

Package Dimensions

• Body Size: 3mm x 3mm (approximate)
• Lead Pitch: 0.65mm
• Height: 1.1mm (maximum)

Pin Configuration

The LM4861 features an 8-pin MSOP package with the following pinout:

• Pin 1 (SHUTDOWN): Active-low shutdown control input.
• Pin 2 (V_DD): Positive power supply input.
• Pin 3 (GND): Ground reference.
• Pin 4 (OUT-): Inverting amplifier output.
• Pin 5 (IN-): Inverting input for the amplifier.
• Pin 6 (IN+): Non-inverting input for the amplifier.
• Pin 7 (BYPASS): Bypass capacitor connection for internal reference voltage.
• Pin 8 (OUT+): Non-inverting amplifier output.

Conclusion

The LM4861 is a highly efficient and compact audio power amplifier designed for applications requiring high-quality sound output with minimal external components. Its bridge-tied load configuration, low power consumption, and thermal protection make it an ideal choice for portable and space-constrained audio systems. With its robust electrical characteristics and surface-mount packaging, the LM4861 offers a reliable and high-performance solution for modern audio applications.