Overview
The LM49450SQ/NOPB from Texas Instruments is a highly integrated audio subsystem designed for portable media player applications. This device combines a 24-bit I2S digital-to-analog converter (DAC), 2.5W/channel stereo Class D speaker drivers, 36mW stereo ground-referenced headphone drivers, volume control, and TI’s unique 3D sound enhancement into a single package.
It features filterless Class D amplifiers that deliver 1.25W/channel into an 8Ω load with less than 1% THD+N at a 5V supply. The LM49450 also includes selectable modulation schemes, including a fixed frequency mode and an EMI-reducing spread spectrum mode.
The device is optimized for low power consumption and high audio quality, making it ideal for applications where space and power efficiency are critical.
Key Specifications
| Parameter | Conditions | Typical Value | Unit |
|---|---|---|---|
| SNR at Headphone Output | - | 102 dBA | - |
| Speaker Amplifier Efficiency at 3.6V | 650 mW/Channel into 8Ω | 87% | - |
| Speaker Amplifier Efficiency at 5V | 1.1 W/Channel into 8Ω | 80% | - |
| Quiescent Power Supply Current (Speaker Mode) | LSVDD = 3.6V | 7.5 mA | - |
| Quiescent Power Supply Current (Headphone Mode) | HPVDD = 2.5V | 5.3 mA | - |
| Output Power/Channel (Speaker) | RL = 4Ω, THD+N ≤ 10% at LSVDD = 5V | 2.5 W | - |
| Output Power/Channel (Speaker) | RL = 8Ω, THD+N ≤ 1% at LSVDD = 5V | 1.25 W | - |
| Output Power/Channel (Headphone) | RL = 16Ω, THD+N ≤ 1% at HPVDD = 2.5V | 34 mW | - |
| Output Power/Channel (Headphone) | RL = 32Ω, THD+N ≤ 1% at HPVDD = 2.5V | 36 mW | - |
| PSRR at 1 kHz (Speaker Mode) | - | 67 dB | - |
| PSRR at 1 kHz (Headphone Mode) | - | 77 dB | - |
| Shutdown Current | - | 0.02 μA | - |
Key Features
- 24-Bit Stereo DAC: Supports a wide range of sample rates including 192kHz, 96kHz, 48kHz, and 44.1kHz.
- Stereo Filterless Class D Operation: Delivers high efficiency and low distortion.
- Selectable Spread Spectrum Mode: Reduces EMI.
- Ground Referenced Headphone Amplifiers: Features 100dB SNR and eliminates the need for DC-blocking capacitors.
- I2S Compatible Audio Interface: Supports left or right justified audio data.
- 32-Step Digital Volume Control: Separate volume control for headphones and speaker outputs.
- I2C Compatible Control Interface: Controls 3D enhancement, mode selection, shutdown, and volume.
- Headphone Sense Input: Automatically detects the presence of a headphone and configures the device accordingly.
- Output Short Circuit and Thermal Overload Protection: Prevents device damage during fault conditions.
- Click and Pop Suppression: Eliminates audible transients on power-up/down and during shutdown.
- Micro-Power Shutdown: Low shutdown current of 0.02 μA.
- Space-Saving 32-Pin WQFN Package: Minimizes system size.
Applications
The LM49450 is primarily designed for portable media player applications, including:
- Portable audio players
- Smartphones and tablets
- Handheld gaming devices
- Wireless speakers and headphones
- Other battery-powered audio devices
Q & A
- What is the maximum output power of the LM49450 in speaker mode?
The LM49450 can deliver up to 2.5W per channel into a 4Ω load with THD+N ≤ 10% at LSVDD = 5V, and up to 1.25W per channel into an 8Ω load with THD+N ≤ 1% at LSVDD = 5V.
- What is the SNR of the headphone output?
The SNR at the headphone output is typically 102 dBA.
- Does the LM49450 support multiple sample rates?
Yes, it supports sample rates up to 192kHz, including 96kHz, 48kHz, and 44.1kHz.
- How does the headphone sense input work?
The headphone sense input (HPS) automatically detects the presence of a headphone and configures the device accordingly.
- What protection features does the LM49450 have?
The device includes output short circuit and thermal overload protection to prevent damage during fault conditions.
- How is the volume controlled on the LM49450?
The volume is controlled through a 32-step digital volume control, separate for headphones and speaker outputs, using an I2C compatible interface.
- What is the shutdown current of the LM49450?
The shutdown current is typically 0.02 μA.
- Does the LM49450 have any EMI reduction features?
Yes, it offers a selectable spread spectrum mode to reduce EMI.
- What package type is the LM49450 available in?
The LM49450 is available in a space-saving 32-pin WQFN package.
- What is the purpose of TI’s 3D enhancement feature?
Texas Instruments’ 3D enhancement feature is designed to improve the audio experience by enhancing the spatial perception of sound.
