Analog Devices’ class-D audio amplifiers for portable electronics

NORWOOD, USA: Analog Devices Inc. (ADI) has introduced a pair of Class-D audio amplifiers for smart phones, GPS units and other handheld electronics where premium sound quality offers a major competitive advantage.

The SSM2375 and SSM2380 amplifiers provide audio system designers with the option of fixed or programmable gain settings combined with low noise and superior audio performance.

The SSM2380 low-power, stereo Class-D amplifier is the first in its class to incorporate an I²C interface, which allows gain stages to be set from 1 dB to 24 dB (plus mute) in 47 distinct steps with no other external components required.

The programmable interface also enables independent L/R channel shutdown, a variable low-EMI (electro-magnetic interference) emission control mode, and programmable ALC (automatic level control) functions for speaker protection. The SSM2380 achieves a 100-dB SNR (signal-to-noise ratio) and extends battery life by achieving 93 percent power efficiency at 5 V while running at 1.4 W into an 8-ohm speaker.

The SSM2375 is a high-performance, fully-integrated Class-D amplifier with single-pin 5-level gain setting in 3-dB stages from 0 dB to 12 dB. The single-pin gain setting eliminates input resistors and ensures a better input match that reduces noise and improves audio quality.

Operating from a single 2.5-V to 5-V supply, the amplifier delivers 3 W of continuous output power with less than 1 percent THD (total harmonic distortion) when driving a 3-ohm load from a 5-V supply.

The SSM2375 offers greater than 98-dB SNR performance and at 215 Hz achieves an 80-dB PSRR (power-supply rejection ratio) that is 10 dB higher than the closest competing Class-D amplifier. The amplifier’s low noise and EMI allow engineers more flexibility to place the speaker on the board in end product designs.