10W stereo Class-D audio amplifier has anti-clipping and spectrum-spreading

Diodes has introduced a 10+10W stereo Class-D audio amplifier with an anti-clipping circuit to avoid distortion at high volume settings and output spectrum-spreading to improve EMC.

Diodes-PAM8106

Called PAM8106, the amplifier is aimed at wireless loudspeakers, LCD TVs, portable stereos, and game machines.

Operation is from 4.5 to 15V and efficiency of up to 92%, the last of which cuts heat production to the point that no heatsink is required, said the company.

15mA typical no-load quiescent current, plus the high efficiency, also suits it to battery operation. Maximum quiescent current is 30mA. Mute typically reduces consumption to 11mA, and the shut-down pin takes drain to 25µA max.

Both 8Ω and 4Ω speakers can be driven, with 2x 10W available with 8Ω speakers and a 12V supply.

Outputs are all-n-channel bridges, with boot-strapping from the output switching waveform providing upper gate-drive.

EMI suppression is through spread-spectrum modulation (SSM) of the output switching frequency. “Audio devices based on the PAM8106 can avoid the need for expensive filters on the audio outputs and instead use ferrite bead filters,” according to Diodes.

Clipping reduction is through ‘NCPL’ (non-clipping power limit) technology, “which automatically adjusts the gain to eliminate clipping at the output signal due to high-level input signals”, said Diodes.

How NCPL works is not obvious, and Electronics Weekly has requested clarification.

Protection is included against short-circuit, excessive temperature and rail under-voltage.

Packaging is QFN5x5-32L.


Comments

2 comments

  1. pretty remarkable! Changing the gain in advance of generating a clipped signal is a nice feature…. but does the sudden change in gain produce a transient of its own? Is it any better than soft clipping? I’m tempted to build up one of these just to find out. 🙂

    Also noteworthy: the combination of the terms “audio amp” and “spread spectrum”. Never would have thought that I’d hear these combined!

    • Hi Steve
      I have asked Diodes for clarification on clipping, the data sheet (as far as I could see) missed out a bunch of information.
      It must be tough spreading the spectrum and keeping control of THD. Mind you, Bluetooth speakers have so much signal processing in to make them sound nice, which many of them do, maybe THD is no longer meaningful.
      I seem to remember Zetex had a nice Class-D amplifier before it was bought by Diodes. I wonder if any of that tech went into this.
      The supply voltage range is so good, that power saving with Class-D semms a bit of a no-brainer now, providing harmonics can be kepts out of any radios nearby.

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