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audio/videoZONE Products for the week of May 11, 2009
Analogic Tech Says…
AAT5101: 2.5 W Class D Audio Amplifier Extends Battery Life in Portable Applications
Extremely Low Standby, Quiescent Current, 2.1 V Operation Save Power
Advanced Analogic Technologies Inc. (AnalogicTech), a developer of power management integrated circuits, announced its first Class D audio amplifier. Building on the company’s extensive experience building power management ICs for portable applications, the AAT5101 2.5W Class D audio amplifier delivers dramatic power savings by combining low voltage operation with low quiescent current and standby current an order of magnitude below competitive devices.
“While the Lithium-ion batteries currently used in most portable systems today shutdown at 2.5V, a new generation of batteries coming onto the market are designed to operate at much lower voltages,” says CJ Zhang, product line vice president. “By supporting operation down to 2.1V and offering very low quiescent and standby current, the AAT5101 offers designers of cell phones, notebooks, GPS and navigation devices an opportunity to significantly reduce power requirements and extend battery life.”
Reduced Operating Voltage
This new mono class D audio power amplifier operates across a wide 2.1V to 5.5V supply voltage making it ideal for systems using next generation low voltage Li-ion/polymer batteries. To further extend battery life, the audio amplifier delivers up to 92 percent efficiency and offers a very low 0.06 µA shutdown current and 1.35 mA quiescent current.
EN-Genius Says…
If you are designing power management products with switching circuits then getting into Class-D audio products is probably a no-brainer.
The AAT5101 is directed at the mono portable market, of course, offering 1.35 W (at 5.0 V with 1 kHz into 8 Ω) falling to 0.29 W at 2.5 V. Sticking with 8 Ω numbers, pushing 1.2 W out, with 5 V, gives an efficiency of 92%, dropping to about 90% at 200 mW out (a more realistic listening level). The efficiency with a 2.1 V rail is about 85% and the device can just about deliver 200 mW. The supply current is about 260 mA (1.2 W, 5 V) and 50 mA (200 mW, 5 V) while the 2.1 V current draw for 200 mW is a wicked 110 mA.
PSRR is better than -55 dB up to about 10 kHz; it then falls rapidly to less than -50 dB at 20 kHz. CMRR is about -60 dB at 1 kHz.
The architecture of the AAT5101 is with a fully differential analog input that can be either dc- or ac-coupled. With ac-coupling the choice of input capacitors will, of course, affect the low-frequency performance but in the portable market that is not very important in the majority of applications. The choice of input resistors sets the gain of the amplifier in conjunction with the feedback resistors on the input stages, with gain = 300 kΩ ÷ R, with R the value of the input resistors – which must be closely matched to maintain the correct output swing around the reference and to maximize CMRR and PSRR, especially if the inputs are used single-ended. The PWM switching frequency is a nominal 250 kHz. Decoupling is important with a Class-D amplifier and AnalogicTech recommend a ceramic 4.7 µF. The output is an H-Bridge and the company has joined in with the “filterless” marketing noise… They do, however add a recommendation for a couple of ferrite beads, but what is not said in the data sheet is that those beads should be as close to the device as possible.
Thermal and short-circuit protection are included, as is a proprietary pop and click suppression system.
AnalogicTech’s first product is aiming at a niche that has other players in it but they are getting their feet into the market with very low pricing. Some competitive parts at similar performance points (ignoring better THD+N numbers) are National’s LM4671 (2.4 V to 5.5 V) priced at $0.44 in 1000 piece lots, and Maxim’s MAX9759 (3 V to 5.5 V) priced at $0.75, also in 1000-piece lots. The AAT5101 is more than 30% less than the LM4671 and more than 60% less than MAX9759. Gutsy or silly? Time will tell, but if the company gets known for killing street pricing, it will be expected by buyers to always be the lowest price on the block. National will certainly match pricing, Maxim will not. The 2.1 V operation could be a really big deal in the market – it certainly would be to the consumer who buys the end product, if he/she knew what it meant in battery life terms; it is probably worth a premium.
The AAT5101 is in production in WLCSP-9 priced at $0.28 in 1000-piece lots.
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