Texas Instruments LM4549BVHX

Overview

LM4549BVHX from Texas Instruments is a dual-channel AC '97 Rev 2.1 audio codec IC with integrated 18-bit sigma-delta ADCs and DACs, 90 dB ADC dynamic range, 89 dB DAC dynamic range, and programmable sample rate conversion from 4 kHz to 48 kHz in 1-Hz steps. It serves as the analog front-end for PC audio systems, supporting stereo recording/playback, TI 3D Sound enhancement, and multi-input mixing (MIC1/MIC2, LINE_IN, AUX, CD, VIDEO, PHONE, PC_BEEP) into LINE_OUT, LNLVL_OUT, and MONO_OUT.

For engineers reviewing the LM4549BVHX datasheet, LM4549BVHX pinout, LM4549BVHX application, or LM4549BVHX equivalent, key selection considerations include its AC Link interface compliance, deterministic sample timing for real-time audio scheduling, extended temperature operation (−40°C to 85°C), dual digital supply support (3.3 V/5 V), and EAPD-controlled external amplifier power-down capability.

Technical Context

The LM4549BVHX implements a fully AC '97 Rev 2.1–compliant architecture with separate stereo ADC and DAC paths, each using 18-bit sigma-delta modulation. Its analog signal chain includes programmable gain amplifiers (0 dB/20 dB mic boost), 1.5-dB-step volume control across eight input channels, and three independent analog mixers (Stereo Mix, Stereo Mix 3D, Mono Mix) feeding three output paths.

Digital interface operates via AC Link with BIT_CLK (12.288 MHz in primary mode), SYNC (48 kHz frame marker), SDATA_IN (controller-to-codec), and SDATA_OUT (codec-to-controller). The device supports up to 8 simultaneous input streams and 2 output streams in extended AC Link configurations, with register-based control over all analog functions and power states.

Key Specifications

Pinout & Package

LM4549BVHX is housed in a 48-pin LQFP package (7.00 mm × 7.00 mm) with exposed thermal pad. Pin functions are defined per TI SNAS598B Rev B datasheet, including dedicated AC Link I/O, analog input/output terminals, crystal oscillator interface, and identity/configuration pins.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar audio codec applications.

Compared with LM4549BVHX, LM4550B adds output channel count but shares identical analog performance and control architecture, while ALC262 trades deterministic timing and industrial specs for integrated jack detection - making LM4549BVHX the preferred choice for deterministic, temperature-hardened, or multi-codec AC Link systems.

Availability

LM4549BVHX is available at Aetrix Electronics and suitable for desktop PC audio systems, portable PC audio subsystems, automotive telematics modules, and general multichannel audio frequency systems requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for LM4549BVHX 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

Texas Instruments is a global semiconductor company specializing in analog and embedded processing technologies, with leadership in precision analog, power management, and signal chain solutions.

The LM4549BVHX belongs to TI's AC '97 audio codec product line, engineered specifically to deliver high-fidelity, low-latency, and deterministic audio conversion for PC99-compliant and industrial-grade computing platforms.

FAQ

What is the primary function of the LM4549BVHX in an AC '97 audio system?

The LM4549BVHX serves as the analog-intensive front-end codec in AC '97 Rev 2.1–compliant systems, performing simultaneous stereo analog-to-digital conversion (ADC) and digital-to-analog conversion (DAC) with 18-bit sigma-delta modulators. It manages all analog signal routing - including mic boost, multi-input mixing, volume control, and TI 3D Sound enhancement - while interfacing digitally via AC Link to the host controller. Its role is to offload analog complexity from the digital controller and ensure deterministic timing for real-time audio tasks.

Does the LM4549BVHX support sample rate conversion, and how is it configured?

Yes, the LM4549BVHX supports independent sample rate conversion for both ADC and DAC paths, programmable from 4 kHz to 48 kHz in precise 1-Hz increments. Configuration is performed through dedicated registers (e.g., Sample Rate Register at 2Ch) accessible via AC Link. This eliminates the need for external SRC chips and enables seamless interoperability between mismatched clock domains - a critical feature for systems integrating legacy audio sources or non-standard controllers. The LM4549BVHX maintains deterministic sample timing regardless of selected rate.

How does the EAPD pin on the LM4549BVHX function, and what is its default state?

The EAPD (External Amplifier Power Down) pin on the LM4549BVHX is an active-high logic output controlled by bit D15 of the Powerdown Control/Status register (26h). Its default state after cold reset is low, enabling connected external power amplifiers. During cold reset, this default allows PC_BEEP signals to pass directly to LINE_OUT outputs before software initialization. Engineers use EAPD to coordinate amplifier shutdown during system sleep modes, reducing standby power consumption. The pin's voltage level follows DVDD, ensuring compatibility with 3.3 V or 5 V amplifier control inputs.

Can the LM4549BVHX operate in multi-codec AC Link configurations, and how is addressing handled?

Yes, the LM4549BVHX supports multi-codec AC Link topologies using ID0# and ID1# pins to configure primary or secondary codec identity. These inverted-polarity inputs set bits D14–D15 in the Extended Audio ID register (28h), assigning the device to one of four slots (Primary, Secondary 0–2). In extended mode, the LM4549BVHX can receive two output streams while transmitting up to eight input streams - enabling scalable channel expansion. This capability is documented in TI SNAS598B Section 5 and requires proper AC Link controller support for slot arbitration.

What are the key analog performance specifications of the LM4549BVHX, and under what conditions are they measured?

The LM4549BVHX delivers 90 dB typical ADC dynamic range and 89 dB typical DAC dynamic range, measured at AVDD = 5 V, DVDD = 3.3 V, Fs = 48 kHz, and TA = 25°C. Its analog loopthrough path (e.g., CD input to LINE_OUT) achieves 97 dB typical dynamic range and 0.013% THD+N at −3 dB output, 1 kHz. Input impedance exceeds 10 kΩ across all analog inputs, and crosstalk between CD channels is ≤−95 dB. These values are production-characterized per TI SNAS598B Section 7.5 and reflect actual design margins, not just typical bench measurements.