Analog Devices Inc. MAX98415A/MAX98425A Stereo Class-D Amplifiers
Analog Devices MAX98415A/MAX98425A Stereo Class-D Amplifiers are high-efficiency, stereo Class-D speaker amplifiers with industry-leading quiescent power featuring Envelope Tracking control, a Brownout Prevention Engine (BPE), Dynamic Headroom Tracking (DHT), and an RMS Limiter. MAX98415A includes precision output current monitoring (ISENSE) and speaker feedback voltage (VFEEDBACK) to enable speaker protection algorithms that a host device can run. Both devices support sample rates up to 192kHz and a higher passband (for fS > 50kHz) to enable high-resolution audio and ultrasound cases. A separate bypass path is available for inputs, such as an ultrasound signal, so audio processing does not attenuate it. SSM and edge rate control minimize EMI and eliminate the need for output filtering in traditional Class-D devices.
The Envelope Tracking algorithm on the devices monitors the incoming audio signal and generates a PWM signal to control an external DC-DC converter. This feature keeps the amplifier supply close to the peak output audio signal, improving system efficiency, idle quiescent power consumption, and thermal efficiency.
The BPE helps avoid a system brownout for battery-powered applications by reducing the device’s current consumption. This feature is achieved by attenuating or limiting the amplifier output when the device supply drops below a set of programmable thresholds. In addition, as the amplifier supply varies due to sudden transients and declining battery life, DHT automatically optimizes the headroom available to the amplifier to maintain a consistent distortion level.
The Analog Devices MAX98415A/MAX98425A provides a PCM interface for audio data and a standard I2C interface for control data communication. When enabled, thermal foldback automatically reduces the output power when the temperature exceeds a user-specified threshold. This feature allows for uninterrupted music playback even at high ambient temperatures. Traditional thermal protection is also available in addition to robust overcurrent protection.
Features
- Wide 3V to 22V input supply range
- Ultra-low quiescent power
- 155mW at VPVDD = 20V, MAX98415A
- 89mW at VPVDD = 14V, MAX98425A
- Ultra-low 28.5μVRMS output noise
- Low distortion of -81.1dB THD+N at 2W into 8Ω, f = 1kHz
- MAX98415A output power at 1% THD+N
- 27W stereo into 8Ω, VPVDD = 22V
- 19W into 4Ω, VPVDD = 14V
- MAX98425A output power at 1% THD+N
- 28W stereo into 8Ω, VPVDD = 22V
- 20.5W into 4Ω, VPVDD = 14V
- MAX98415A speaker amplifier efficiency
- 87.0% at 1W per channel into 8Ω, VPVDD = 22V
- 87.0% at 1W per channel into 4Ω, VPVDD = 14V
- MAX98425A speaker amplifier efficiency
- 87.5% at 1W per channel into 8Ω, VPVDD = 22V
- 88% at 1W per channel into 4Ω, VPVDD = 14V
- Class-D EMI reduction enables filterless operation
- SSM and switching edge rate control
- Integrated speaker current and voltage feedback, does not require external components (MAX98415A only)
- Flexible brownout prevention engine
- I2S/16-channel TDM and I2C digital interfaces
- Playback and IV paths support sample rates up to 192kHz
- No MCLK required
- Dynamic Headroom Tracking (DHT)
- Envelope tracking output to maximize system efficiency
- Extensive click-and-pop suppression
- 40-bump WLP (0.4mm pitch) package
Applications
- Soundbars
- Mobile speakers and smart speakers
- Tablets, laptops, and desktop computers
- Smart Internet of Things (IoT) devices
MAX98415A Block Diagram
MAX98425A Block Diagram
Development Tools
Analog Devices Inc. MAX98415A/MAX98425A Evaluation Systems
Evaluates the MAX98415A or MAX98425A stereo Class-D audio amplifiers.