Mobile phone users have tired of the mediocre audio performance that has been far too common on handheld products and are demanding that the tiny speakers in their handhelds sound great without draining their batteries. This is nearly a contradiction.
To rise to such a daunting challenge, semiconductor makers have to force disintegration, which seems a bit of a dichotomy for companies that integrate for a living.
Disintegration of audio is defined as pulling audio functions out of the main mobile phone chipsets in order to isolate them. This allows audio performance to evolve faster than if it remained trapped inside cell phone chipsets.
Taking audio external has the additional and important benefit of allowing the audio and cell phone chip set ICs to be built from different process technologies, freeing each to evolve unencumbered by the other’s process requirements.
Repartitioning
Moving functions from one chip to another is called “repartitioning”. The audio blocks that are being repartitioned out of the main mobile phone chipsets often attract fellow travellers, such as power management blocks, which makes perfect sense since the other side of the great sound from small handset speakers equation is the battery-driven environment.
Putting power management plus audio circuits in the same IC is driving IC makers in from different places. Given the range of companies and competencies, the mobile phone audio market is certain to accrue a great deal of innovation.
The notions of power and audio have always gone together. The main measurement of audio prowess in the early audiophile days was power (wattage). But now, with mobile being the most popular audio platform, the concern has become, “How do you get the wattage to drive speakers from a small battery while not draining it so fast that the product is not any fun?”
IC makers have figured out that managing power is the key to fun audio products and mobile phone makers are looking to the IC guys to make it possible.
Several different technical approaches are emerging due to repartitioning.
First is the addition of power management to stand-alone headphone and speaker amps. LDOs, boost and buck DC-DC converters, and battery management circuits are attaching to different classes of audio drivers.
No discussion of audio drivers can really avoid mentioning the alphabet soup of audio amplifier technologies, namely Class AB, Class D, Class G, Class H and various eponymous classes such as Class W.
Audio subsystems
It is still early in the disintegration/reintegration cycle, so several other species of ICs are vying for survival. One is the so-called audio subsystem, which combines headphone amplifiers with speaker amplifiers on a single chip.
The other important example is audio codecs with all kinds of interesting functions packed inside.
Higher output, higher quality, higher efficiency, and higher levels of integration (that should be audio re-integration) have animated the creation and reassembly of different combinations and amplifier types.
The phone audio subsystems now typically start with a Class D amp to drive speakers and then add Class AB, D or G to drive the headphone amps, depending on the particular vendor. While the emerging audio subsystem exemplifies combining technologies, the real mix-and-match nature of audio disintegration/reintegration is seen it its full glory in sophisticated new audio codecs, which are true audio systems in and of themselves.
Codecs
Highly integrated codec systems can bring value to smartphone platforms by providing a range of functionality. Going forward, smartphone codec systems will include a wide array of features, such as headphone and speaker drivers, parametric equalisers, sound mixing, dynamic range control, noise cancelling, beam steering, 3D sound processing, microphone array interfaces and various audio interfaces.
Although the end result is still to be determined, the trend at least is becoming very clear.
Disintegration has freed audio/power management IC engineers to reintegrate a variety of functions into stand-alone amps with power management, audio amp subsystems, and sophisticated audio codec systems.
Author is Bill Boldt, senior marketing manager at Fairchild Semiconductor