LM4991MAX/NOPB

### Texas Instruments LM4991MAX/NOPB Overview

The LM4991MAX/NOPB is a high-performance, low-voltage audio power amplifier designed by Texas Instruments. It is optimized for driving speakers in portable devices such as mobile phones, tablets, and laptops while ensuring high-quality sound reproduction. The LM4991 integrates advanced features to enhance audio performance, efficiency, and usability.

#### Key Features

1. Class D Amplifier: The LM4991 operates as a Class D amplifier, which provides high efficiency (up to 90%) while minimizing heat generation. This makes it ideal for battery-powered applications.

2. Low Supply Voltage: Designed to operate within a supply voltage range of 2.5 V to 5.5 V, the LM4991 is suitable for various portable electronics that require low-power operation.

3. High Output Power: The amplifier can deliver up to 1.4 W of continuous output power into an 8 Ω load, making it capable of driving larger speakers without distortion.

4. Built-in Short-Circuit Protection: The LM4991 features a built-in short-circuit protection mechanism that prevents damage to the device in case of faulty connections or speaker failures.

5. Thermal Shutdown: It includes thermal shutdown capabilities, allowing the amplifier to automatically turn off when excessive heat is detected, protecting both the amplifier and the connected load.

6. Low THD+N: The total harmonic distortion plus noise (THD+N) is kept very low, typically around 0.1%, ensuring high-fidelity audio output.

7. Single-Ended Input: The LM4991 accepts single-ended inputs, simplifying its integration into existing designs without requiring differential signaling.

8. External Gain Control: The amplifier supports external gain control through resistors, providing flexibility in adjusting the output level according to system requirements.

9. Integrated Bypass Capacitor: It allows for reduced component count by integrating a bypass capacitor directly onto the chip, streamlining PCB design.

#### Specifications

- Part Number: LM4991MAX/NOPB
- Amplifier Type: Class D audio amplifier
- Supply Voltage (VDD):
- Minimum: 2.5 V
- Maximum: 5.5 V
- Output Power:
- At 5 V into 4 Ω: 1.5 W (maximum)
- At 5 V into 8 Ω: 1.4 W (maximum)
- Total Harmonic Distortion + Noise (THD+N):
- Typical: 0.1% at 1 W, 1 kHz
- Efficiency: Up to 90%
- Input Resistance: 20 kΩ (typical)
- Shutdown Current: 1 μA (typical)
- Operating Temperature Range:
- Industrial: -40°C to +85°C
- Package Type: TQFP (Thin Quad Flat Package)
- Pin Count: 32

#### Applications

The LM4991MAX/NOPB is well-suited for a variety of applications, including:

- Portable Audio Devices: Ideal for smartphones, tablets, and laptops where space is limited but sound quality is essential.
- TVs and Monitors: Enhances audio performance in flat-screen TVs and monitors.
- Consumer Electronics: Used in various electronic devices requiring efficient audio amplification.

#### Performance Characteristics

The LM4991%27s performance can be characterized by several parameters:

- Signal-to-Noise Ratio (SNR): Greater than 90 dB, indicating excellent audio clarity.
- Power Supply Rejection Ratio (PSRR): Greater than 65 dB, which helps maintain consistent performance despite variations in the power supply.
- Operating Frequency Range: Up to 22 kHz, making it suitable for a wide range of audio content.

#### Conclusion

The Texas Instruments LM4991MAX/NOPB is a robust and efficient audio amplifier tailored for modern portable devices. Its combination of high output power, low distortion, and thermal protection features make it an optimal choice for designers looking to enhance audio experiences in compact form factors. For more detailed specifications, application notes, and design resources, engineers are encouraged to refer to the Texas Instruments website or consult the product datasheet.