MAX98415A: 22V Stereo Class‑D Amplifier with Digital Input, Ultra‑Low IQ & IV Feedback
The MAX98415A is a high-efficiency, stereo Class-D speaker amplifier with industry-leading quiescent power featuring Envelope Tracking control, Brownout Prevention Engine (BPE), Dynamic Headroom Tracking (DHT), and RMS Limiter. It includes precision output current monitoring (ISENSE) and speaker feedback voltage (VFEEDBACK) to enable speaker protection algorithms that can be run by a host device.
The MAX98415A supports sample rates up to 192kHz and a higher passband (for fS > 50kHz) to enable high-resolution audio and ultrasound use cases. A separate bypass path is available for inputs, such as an ultrasound signal, so that it is not attenuated by audio processing. SSM and edge-rate control minimize EMI and eliminate the need for output filtering found in traditional Class-D devices.
The Envelope Tracking algorithm on the device monitors the incoming audio signal and generates a PWM signal to control an external DC-DC converter to keep the amplifier supply close to the peak output audio signal, thereby improving system efficiency, idle quiescent power consumption, and thermal efficiency.
For battery-powered applications, the BPE helps avoid a system brownout by reducing the device’s current consumption. This is achieved by either 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 device provides a PCM interface for audio data and a standard I2C interface for control data communication.
Thermal foldback, when enabled, automatically reduces the output power when the temperature exceeds a user-specified threshold. This allows for uninterrupted music playback even at high ambient temperatures. Traditional thermal protection is also available in addition to robust overcurrent protection.
Key Features and Benefits
- Wide Input Supply Range (3V to 22V)
- Ultra-Low Quiescent Power
- 155mW at VPVDD = 20V, MAX98415A
- Ultra-Low 28.5μVRMS Output Noise
- Low Distortion
- -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
- MAX98415A Speaker Amplifier Efficiency:
- 87.0% at 1W per ch. into 8Ω, VPVDD = 22V
- 87.0% at 1W per ch. into 4Ω, VPVDD = 14V
- Class-D EMI Reduction Enables Filterless Operation
- SSM and Switching Edge Rate Control
- Integrated Speaker Current and Voltage Feedback, Do 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)
Applications
- Soundbars
- Mobile Speakers and Smart Speakers
- Tablets, Laptops, and Desktop Computers
- Smart IoT Devices
Evaluation Board
The MAX98415A can be evaluated with the MAX98415AEVSYS.
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