基于SSM2380設(shè)計(jì)的D類(lèi)立體聲音頻放大技術(shù)

SSM2380是ADI公司的帶ALC+I2C的無(wú)濾波器2x2W D類(lèi)立體聲音頻放大器,單電源2.5V到5.5V工作,在5.0V電源時(shí)能向4歐姆負(fù)載提供2W連續(xù)輸出功率,而THD+N小于1%,效率為93%,信噪比大于100dB.SSM2380主要應(yīng)用在手機(jī),MP3播放器,手提電子設(shè)備.本文介紹SSM2380主要特性, 功能方框圖, I2C 模式, ALC 模式和增益模式的典型應(yīng)用電路圖及其配置圖.

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SSM2380: 2x2W Filterless Class-D Stereo Audio Amplifier with ALC + I2C

The SSM2380 is a fully integrated, high efficiency, stereo Class-D audio amplifier. It is designed to maximize performance for mobile phone applications. The application circuit requires a minimum of external components and operates from a single 2.5 V to 5.5 V supply. It is capable of delivering 2 W of continuous output power with <1% THD + N driving a 4 ? load from a 5.0 V supply.

The SSM2380 features a highly flexible I²C interface with many useful settings. Using the I²C control interface, the gain of SSM2380 can be selected from 1dB to 24 dB + Mute in 47 steps with no external components. Other features accessed from the I²C interface are: Independent L/R channel shutdown, Variable ultra-low EMI emission control mode, Automatic Level Control (ALC) for high quality speaker protection, and Stereo-to-Mono mixing operation.

The SSM2380 features a high efficiency, low noise modulation scheme that requires no external LC output filters. The modulation continues to provide high efficiency even at low output power. It operates with 93% efficiency at 1.4 W into 8 Ω or 85% efficiency at 2W into 4 Ω from a 5.0 V supply and has an SNR of >100 dB. Spread-spectrum pulse density modulation is used to provide lower EMI-radiated emissions compared with other Class-D architectures. An added benefit of spread-spectrum Σ-Δ modulation is that no synchronization (SYNC) is needed when using multiple Class-D amplifiers. For applications that require long speaker cables (>10cm), the SSM2380 includes a user selectable ultra-low EMI emission mode that eliminates the need for EMI filters at the Class-D outputs.

The SSM2380 has a micropower shutdown mode with a typical shutdown current of 20 nA. Shutdown is enabled by applying a logic low to the SD pin or optional independent channel soft shutdown via I²C.

The device also includes pop-and-click suppression circuitry. This suppression circuitry minimizes voltage glitches at the output during turn-on and turn-off, reducing audible noise on activation and deactivation.

The fully differential inputs of the SSM2380 provides excellent rejection of common-mode noise on the input. Input coupling capacitors can be omitted if the dc input common-mode voltage is approximately V_DD/2.

The SSM2380 is specified over the commercial temperature range (?40℃ to +85℃). It has built-in thermal shutdown and output short-circuit protection. It is available in a 16-lead, 2 mm × 2 mm wafer level chip scale package (WLCSP).

SSM2380主要特性:

Filterless Stereo Class-D amplifier with Delta-Sigma modulation

2 W into 4ohm load and 1.4 W into 8ohm load at 5.0 V supply with <1% total harmonic distortion (THD + N)

Highly Configurable I2C Interface for Gain Adjust, Automatic Level Control (ALC) and Ultra-Low EMI Emission Mode

MODE Pin can disable I2C interface for more traditional stereo amplifier configuration

Stereo-to-Mono mixer option via I2C control

93% efficiency at 5.0 V, 1.4 W into 8ohm speaker

>100 dB signal-to-noise ratio (SNR)

Single-supply operation from 2.5 V to 5.5 V

20 nA ultralow shutdown current

Short-circuit and thermal protection

Pop-and-click suppression

Available in 16-ball, 2.0 mm × 2.0 mm WLCSP

SSM2380應(yīng)用:

Mobile phones

MP3 players

Portable electronics


圖1.SSM2380功能方框圖

圖2.SSM2380典型應(yīng)用電路– I2C 模式

圖3.SSM2380增益配置(MODE引腳=GND)

圖4.SSM2380典型應(yīng)用電路– ALC 模式

圖5.SSM2380 ALC運(yùn)行配置(MODE引腳=開(kāi)路/不接)

圖6.SSM2380典型應(yīng)用電路– 增益模式

圖7.SSM2380 增益運(yùn)行配置(MODE引腳=VDD)