Low Power, High Fidelity Audio Solutions for Smart Home
Featured Technical Article
Low power audio is becoming a popular alternative to power-hungry visual displays on battery-powered devices. This design solution leverages the Class-D digital audio amplifier in a cleverly packaged IC, which requires minimal configuration.
The MAX98090 is a fully integrated audio codec whose high-performance, ultra-low power consumption and small footprint make it ideal for portable applications.
The device features a highly flexible input scheme with six input pins (WLP) that can be configured as analog or digital microphone inputs, differential or single-ended line inputs, or as full-scale direct differential inputs. Analog inputs can be routed to the record path ADC or directly to any analog output mixer.
The device accepts master clock frequencies of either 256 x fS or from 10MHz to 60MHz. The digital audio interface supports master or slave mode operation, sample rates from 8kHz to 96kHz, and standard PCM formats such as I2S, left/right-justified, and TDM.
The record/playback paths feature FlexSound® technology DSP. This includes digital gain and filtering, a biquad filter (record), dynamic range control (playback), and a seven band parametric equalizer (playback) that can improve loudspeaker performance by optimizing the frequency response.
The stereo Class D speaker amplifier provides efficient amplification, features low radiated emissions, supports filterless operation, and can drive both 4Ω and 8Ω loads. The DirectDrive® stereo Class H headphone amplifier provides a ground referenced output eliminating the need for large DC-blocking capacitors. The device also includes a differential receiver (earpiece) amplifier that can be reconfigured as a stereo single-ended line output.
The MAX98365 is an easy-to-use, low-cost, digital input Class-D amplifier that provides industry-leading, Class-AB audio performance with Class-D efficiency. The digital audio interface automatically recognizes different PCM and TDM clocking schemes which eliminates the need for I2C programming: Simply supply power, LRCLK, BCLK, and digital audio to generate sound. Furthermore, a novel pinout allows customers to use the cost-effective wafer-level package (WLP) with no need for expensive in-pad vias. A wide 3V to 14V supply range allows the device to deliver 13.8W into an 8Ω load.
The digital audio interface is highly flexible. The devices support I2S, left-justified, and 8-channel time division multiplexed (TDM) data formats. The digital audio interface accepts 8kHz, 16kHz, 32kHz, 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, and 192kHz sample rates. Data words can be 16-bit, 24-bit, or 32-bit in I2S and left-justified modes and 16-bit or 32-bit in TDM mode.
Digital audio interface input thresholds are ideal for interfacing to 1.2V and 1.8V logic. The devices can tolerate logic input voltages up to 5.5V.
The MAX98365A and MAX98365B have fast 1ms turn-on times while the MAX98365C and MAX98365D ramp the volume over 13ms during turn-on and turn-off.
The devices eliminate the need for the external MCLK signal that is typically used for PCM communication. This reduces EMI and possible board coupling issues in addition to reducing the size and pin count. The devices also feature a very high wideband jitter tolerance (12ns, typ) on BCLK and LRCLK to provide robust operation.
Active emissions-limiting, edge-rate limiting, and overshoot control circuitry greatly reduce EMI. A filterless spread-spectrum modulation scheme eliminates the need for output filtering found in traditional Class-D devices and reduces the component count of the solution.
The devices are specified over the -40°C to +85°C temperature range.
- Smart Speakers
- Notebook Computers
- IoT Devices
- Gaming Devices (Audio and Haptics)
The MAX98396 is a high-efficiency, mono Class-DG speaker amplifier with industry-leading quiescent power featuring I/V sense, brownout-prevention engine (BPE), and dynamic-headroom tracking (DHT). The IC 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 and voltage monitoring (I/V sense) enables the host device to run speaker protection algorithms. 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 amplifier employs two supply rails VBAT (3V to 5.5V) and PVDD (3V to 20V) 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. The brownout-prevention engine in the device allows it to reduce its contribution to the overall system power consumption by either attenuating or limiting the amplifier output when the device supply drops below a set of programmable 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 TDM audio data formats. A unique clocking structure eliminates the need for an external master clock for PCM communication, which reduces pin count and simplifies board layout. Enabling thermal foldback 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.
- Mobile Speakers
- Smart Speakers
- Smart IoT
- Notebook Computers
Featured Evaluation System
The MAX98396 evaluation system (EV system) evaluates the MAX98396 Mono Class-D Audio Amplifier featuring Dynamic Headroom Tracking (DHT) and Clock-and-Data Monitoring. The EV system consists of the MAX98396 Development Board (DEV board), Audio Interface Board III (AUDINT3), a micro-USB cable, and the MAX98396 evaluation software.
It is recommended that the DEV board be evaluated with the AUDINT3 board as an EV system. The MAX98396 supports standard I2S, left-justified, and TDM digital audio interfaces, as well as I2C for control.
The AUDINT3 board provides the USB-to-PCM and USB-to- I2C interfaces in addition to the 1.8V AVDD supply and the 1.2V DVDD and DVDDIO supplies that are needed to evaluate the DEV board. The IC DEV board requires two additional supply inputs, 3V to 5.5V (VBAT) and 3V to 20V (PVDD). Figure 1 details the DEV board and the AUDINT3 board.
- Notebook Computers
- Portable Speaker
- Smart IoT
- Smart Speaker