28V Digital Input, Class-DG Amplifier with IV, Ultra-Low I, and Brownout Prevention

The MAX98397 is a high-efficiency, mono Class-DG speaker amplifier with industry-leading quiescent power, featuring integrated speaker current and voltage sensing (IVSENSE), a brownout-prevention engine (BPE), and dynamic-headroom tracking (DHT). The device also enables ultrasound applications by providing support for sample rates up to 192kHz, a higher passband (for fS > 50kHz), and a bypass path for the ultrasound signals through the amplifier so it is not attenuated by the audio processing. Precision output current monitoring (ISENSE) and voltage monitoring (VSENSE) enable speaker protection algorithms to be run by a host device. Spread-spectrum modulation (SSM) and edge rate control minimize EMI and eliminate the need for the output filtering found in traditional Class-D devices.

To achieve industry-leading quiescent power, the Class-DG architecture employs two supply rails; VBAT (3V to 5.5V) and PVDD (3V to 28V) to supply the speaker amplifier. The Class-DG amplifier switches between the two supply rails depending on the input signal level and/or the supply headroom.

For battery-powered applications, the BPE is designed to help prevent the possibility of a system brownout by reducing the device's contribution to the overall system power consumption. This is achieved by either attenuating or limiting the amplifier output when the device supply drops below a set of programmable BPE thresholds. Additionally, as the power-supply voltage varies due to sudden transients and declining battery life, DHT automatically optimizes the headroom available to the Class-DG amplifier to maintain consistent distortion and listening levels.

The device provides a PCM interface for audio data and a standard I2C interface for control data communication. The PCM interface supports audio playback using I2S, left-justified, and time-division multiplexing audio data formats. A unique clocking structure eliminates the need for an external system clock (MCLK) for PCM communication, which reduces pin count and simplifies board layout.

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.

The device is available in a 0.4mm pitch, 35-bump wafer-level package (WLP). The device operates over the extended -40°C to +85°C temperature range.

Application

* Mobile Speakers and Smart Speakers

* Tablets, Laptop and Desktop Computers

* Soundbars

* Smart IOT

* Wide Input Supply Range (3V to 28V)

* Class-DG Operation Enables Industry Leading Quiescent Power

* 21mW at VPVDD = 20V, VVBAT = 3.8V

* 25.3mW at VPVDD = 24V, VVBAT = 5.0V

* Ultra-Low Noise Floor

* 21.5μVRMS Output Noise

* 117.8dB Dynamic Range

* Low Distortion

* -85dB THD+N at 3W into 8Ω, f = 1kHz

* -85dB THD+N at 6W into 4Ω, f = 1kHz

* -80dB THD+N at 1W into 8Ω, f = 6kHz, FSW = 650kHz

* Output Power:

* 42W into 8Ω, VPVDD = 28V, THD+N = 1%

* 26W into 4Ω, VPVDD = 16V, THD+N = 1%

* 51W into 8Ω, VPVDD = 28V, THD+N = 10%

* 100W Peak Output Power into 4Ω, VPVDD = 28V

* Speaker Amplifier Efficiency:

* 83% at 1W into 8Ω, VPVDD = 24V