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Said to be the world's first standalone Class-G headphone amplifiers, the LDS9505 and LDS9504 are optimised for ultra-low power dissipation that dramatically increases the battery run-time. Similar to earlier Leadis audio products, the LDS9505 and LDS9504 incorporate the proprietary Gmax amplification technology. Both audio ICs feature the new Leadis Adaptive Rail Amplifier (ARA) advanced proprietary charge-pump technology. The ARA tracks the envelope of the audio signal in realtime to dynamically adjust internally generated power supply rails. Minimizing the voltage drop from the power supply rails to the audio waveform envelope eliminates wasted power found in other headphone amplifiers solutions.

The LDS9505 and LDS9504 require a total of 4mW quiescent power, with ultra-low 5.5mW power dissipation per channel at typical headphone listening levels (2x0.5mw). Additionally, the devices are capable of up to 63mW in single-ended stereo and 106mW in mono BTL output, with 102dB S/N ratio.

Using both Leadis’ Gmax and ARA technologies, the LDS9505 and LDS9504 retain the benefit of analog amplifiers (no filters and high signal quality), with a fraction of the power dissipation. Using a combination of advanced on-chip designs, “pop and click” sounds during device power-up and the “zipper-noise” when the volume is changed are reduced to virtually zero on the LDS9505 and LDS9504. The audio ICs have ground-centered outputs that require no output capacitors. This reduces systems cost and board space, while dramatically increasing bass response. Using integrated charge pump circuitry to bias the headphone sleeve to true ground eliminates ground-loop issues that can occur when connecting the output to devices other than headphones, such as audio docking stations.

“Portable audio manufacturers want increased performance while demanding longer battery life, which creates a challenging design scenario,” said Greg Davis, senior director of Leadis’ Audio Business Unit. “Our LDS9505 and LDS9504 headphone amplifiers solve this issue by squeezing out every possible minute of battery run-time so a smaller battery can be used.”

Both units feature an integrated LDO that allows direct connection to Li-ion batteries and a power supply rejection ratio (PSRR) of over 100dB to effectively eliminate GSM phone interference.

The LDS9505 includes a 64 step audio-taper volume control (-59.5dB to +4dB) while the LDS9504 implements convenient pin-selectable fixed gains. An I2C interface controls all device functions including low-power standby, independent headphone mute/enable, headphone mono/stereo, differential or BTL output modes, and a high impedance output. The I2C registers can also be read to verify programming and headphone detection.

Both audio ICs are packaged in a standard 20-pin 4mmx4mm QFN or in ultra-small chip-resistant Super-CSP 1.8mmx2.3mm packaging. Samples are available now, with mass-production quantities available in Q3.