Ultra Low Power, Class-D Audio Amplifier

The SSM6515 is a fully integrated, high efficiency, mono Class-D audio amplifier with digital input that is ideally suited for use in wireless headphones. The application circuit requires few external components and operates from a 1.8 V (PVDD) supply and a 1.2 V to 1.8 V (IOVDD) supply. With 1.8 V signaling, these can be shared. It can deliver 85 mW of continuous output power into a 16 Ω load with <1% total harmonic distortion plus noise (THD + N).

The SSM6515 features a high efficiency, low noise modulation scheme that requires no external inductor/capacitor (LC) output filters. This scheme continues to provide high efficiency even at very low output power resulting in battery life savings compared to conventional headphone amplifiers. The device operates with > 90% efficiency at 55 mW into a 16 Ω load and it has a signal-to-noise ratio (SNR) of 113 dB, A weighted. Spread spectrum, stable common-mode pulse density modulation provides a much lower electromagnetic interference (EMI) radiated emissions compared with other Class-D architectures.

The digital input eliminates the need of an external digital-to-analog converter (DAC). The SSM6515 has a micropower shutdown mode with a typical shutdown current of 6 μA at the 1.8 V PVDD supply and can automatically power down with no input. The device also includes pop and click suppression circuitry that minimizes voltage glitches at the output during turn on and turn off. Inputs support various serial audio formats, including I2S, time division multiplexing (TDM), and pulse density modulation (PDM).

The SSM6515 is designed to operate with an I2C control interface or in standalone mode and specified over the temperature range of −40°C to +85°C. The device has built-in output short-circuit protection. The SSM6515 is available in a halide free, 11-ball, 0.984 mm × 1.444 mm, 0.35 mm pitch wafer-level chip scale package (WLCSP).

APPLICATIONS

* Wireless headphones

* Active noise canceling headphones

* Smartphone earpiece speakers

* Hearing assistance devices

* Portable electronics

* Filterless digital input, mono differential output Class-D amplifier with 3-level Σ-Δ modulation optimized for headphone drive

* Operates from single 1.8 V supply

* 80 mW output power, 16 Ω load at <0.1% THD + N

* 2.57 μV rms noise, 113 dB A weighted signal-to-noise ratio and dynamic range

* 0.003% THD + N at 30 mW, 1 kHz output 32 Ω load

* I2C control with up to 4 pin selectable addresses or standalone operation

* Multiple serial data formats

* TDM, I2S, or left justified slave

* PDM input operating from 2.8224 MHz to 12.288 MHz

* Support sample rates from 8 kHz to 768 kHz

* 3.9 μs latency with 6 MHz PDM input