The MAX98355A/MAX98355B are digital pulse-code modulation (PCM) input class D power amplifiers that provide class AB audio performance with class D efficiency. These ICs offer five selectable gain settings (3 dB, 6 dB, 9 dB, 12 dB, and 15 dB) set by a single gain-select input (GAIN).
The digital audio interface is highly flexible with the MAX98355A supporting I²S data and the MAX98355B supporting left-justified data. Both ICs support time-division-multiplexed (TDM) data. The digital audio-interface accepts sample rates ranging from 8 kHz to 96 kHz for all supported data formats. The ICs can be configured to produce a left-channel, right-channel, or (left + 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 data with up to four slots when 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 (12 ns 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 a 9-pin WLP package (1.345 mm x 1.435 mm x 0.64 mm) and are specified over the -40°C to 85°C temperature range.
- Single-supply operation (2.5 V to 5.5 V)
- 3.2 W output power into 4 Ω at 5 V
- 2.2 mA quiescent current
- 92% efficiency (RL = 8 Ω, POUT = 900 mW, VDD = 3.7 V)
- 25 μVRMS output noise (AV = 15 dB)
- Low 0.013% THD+N at 1 kHz
- No MCLK required
MAX98355 Power Amplifiers