Class-D Audio Amplifiers with Integrated Boost Converters Enable High-Quality and Power-Efficient Sound Systems
By: Leo Zhang, Audio Marketing Manager
The accessibility of audio applications means that music and smart technology are everywhere: commuters listen to music on their earbuds while traveling and a home’s smart speakers make it easy to talk to AI-enabled personal assistants in any room. Alongside the convenience of portable and battery-powered audio equipment that pair with their cell phones, consumers increasingly care about the audio quality of the music, personal assistants, or battery-powered Bluetooth® speakers that they listen to.
In the past, traditional Bluetooth speakers used a separate boost voltage converter to the Class-D amplifier—but this solution required a relatively large PCB area with a high bill of materials (BOM) and potentially long delivery times. In addition, the boost converter and audio amplifier’s switching frequencies may not synchronize, thus causing unexpected noise if the design was not robust enough to compensate.
Resolving these issues, the PAM8965 is a stereo power amplifier with an integrated synchronous boost converter, which reduces the required board space and minimizes overall BOM cost. The device provides exceptionally high efficiency of up to 92% (including boost converter), which maximizes the time between battery charges. A low quiescent current of only 10mA also helps increase battery life at low output power. Running off a 2.8V to 8.5V power supply, the device can be powered by one 18650 battery or two 18650 batteries in series.
The PAM8965 features spread spectrum modulation (SSM), which results in more effective EMI suppression across a broad range of frequencies. This allows the use of inexpensive ferrite bead filters, rather than more costly and bulky LC filters using large inductors and capacitors that traditional Class-D amplifiers require—again, reducing the total BOM cost.
In terms of audio quality, the PAM8965 enjoys excellent figures. Total harmonic distortion plus noise (THD+N) is 0.035% at 5W stereo output power, and signal-to-noise ratio (SNR) is 100dB. Output integrated noise (A-weighted) at a gain of 20dB is 50μV, and there is no pop noise at power on/off, or shutdown enable/disable.
The amplifier helps ensure reliable operation with multiple protection features for the speakers and the overall system. These include non-clip power limit (NCPL), thermal foldback that reduces output power if the amplifier starts to overheat, and DC-input detection that disables the audio output. The PAM8965 also possesses overvoltage, undervoltage, and short-circuit protection on all audio circuits.
There is no denying that consumers expect audio quality in portable systems to continually improve. With an optimum balance of quality, efficiency, and cost, the new PAM8965 Class-D amplifier with synchronous boost converter is the ideal solution to help OEMs achieve this goal.
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