Description générale

The MAX98357A/MAX98357B is an easy-to-use, low-cost, digital pulse-code modulation (PCM) input Class D amplifier that provides industry-leading Class AB audio performance with Class D efficiency. The digital audio interface automatically recognizes up to 35 different PCM and TDM clocking schemes which eliminates the need for I2C programming. Operation is further simplified by eliminating the need for an external MCLK signal that is typically used for PCM communication. Simply supply power, LRCLK, BCLK, and digital audio to generate audio! Furthermore, a novel pinout allows customers to use the cost-effective WLP package with no need for expensive vias.

The digital audio interface is highly flexible with the MAX98357A supporting I2S data and the MAX98357B supporting left-justified data. Both ICs support 8 channel time division multiplexed (TDM) data. The digital audio interface accepts specified sample rates between 8kHz and 96kHz for all supported data formats. The ICs can be configured to produce a left channel, right channel, or (left/2 + right/2) output from the stereo input data. The ICs operate using 16/24/32-bit data for I2S and left-justified modes as well as 16-bit or 32-bit data using TDM mode.

The ICs 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 of the ICs.

The ICs 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 ICs are available in 9-pin WLP (1.345mm x 1.435mm x 0.64mm) and 16-pin TQFN (3mm x 3mm x 0.75mm) packages and are specified over the -40°C to +85°C temperature range.

 

Description détaillée

The MAX98357A/MAX98357B are digital PCM input Class D power amplifiers. The MAX98357A accepts standard I2S data through DIN, BCLK, and LRCLK while the MAX98357B accepts left-justified data through the same inputs. Both versions also accept 16-bit or 32-bit TDM data with up to eight slots. The digital audio interface eliminates the need for an external MCLK signal that is typically required for I2S data transmission.SD_MODE selects which data word is output by the amplifier and is used to put the ICs into shutdown. These devices offer five gain settings in I2S/left-justified mode and a fixed 12dB gain in TDM mode. Channel selection in TDM mode is set with the combination of SD_MODE and GAIN_SLOT.

The MAX98357A/MAX98357B DAI includes a DC blocker with a -3dB cutoff at 3.7Hz.

The MAX98357A/MAX98357B feature low-quiescent current, comprehensive click-and-pop suppression, and excellent RF immunity. The ICs offer Class AB audio performance with Class D efficiency in a minimal boardspace solution. The Class D amplifier features spreadspectrum modulation with edge-rate and overshoot control circuitry that offers significant improvements in switchmode amplifier radiated emissions. The amplifier features click-and-pop suppression that reduces audible transients on startup and shutdown. The amplifier includes thermaloverload and short-circuit protection.

Digital Audio Interface Modes

The input stage of the digital audio interface is highly flexible, supporting 8kHz–96kHz sampling rates with 16/24/32-bit resolution for I2S/left justified data as well as up to a 8-slot, 16-bit or 32-bit time division multiplexed (TDM) format. When LRCLK has a 50% duty cycle the data  format is determined by the part number selection (MAX98357A/MAX98357B). When a frame sync pulse is used for the LRCLK the data format is automatically configured in TDM mode. The frame sync pulse indicates the beginning of the first time slot.

MCLK Elimination

The ICs 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 of the ICs.