First Stereo Analog Subsystem for Mobile Handsets
with Class G Headphone Amp and Loudspeaker Protection
PowerWise Subsystemís Class G Headphone Amp Extends
SANTA CLARA, Calif.– February 23, 2011
–National Semiconductor Corp. today announced the industry’s
first stereo analog subsystemwith integrated Class G headphone
amplifier and automatic level control (ALC) for smartphones
and feature phones. The PowerWise LM49251’s Class G
headphone amp dynamically reduces the supply voltage to lower
power consumption and extend audio (MP3, movies, etc.) playback
time. The loudspeaker’s ALC provides designers with
several options to control audio distortion levels and prevent
National’s LM49251 stereo analog subsystem combines
a 1.4W Class D speaker amplifier, 20 mW Class G headphone
amplifier and ALC in an ultra-small 2.55 mm by 3.02 mm package.
The LM49251 offers thelowest power consumption in its class,
consuming less than 7 mA of quiescent current at 3.3V for
the loudspeaker and headphone. The LM49251’s ALC feature
provides designers with a programmable output power limiter
for speaker protection and clip level select.
Key Technical Features – LM49251 Stereo Analog
Offered in a 30-bump micro SMD package, the LM49251 provides
enhanced Emission Suppression (E2S) and a Class D amplifier
featuring a patented, ultra-low EMI pulse-width modulation
(PWM) architecture that significantly reduces RF emissions
while preserving audio quality. The LM49251’s Class
G headphone architecture significantly increases audio playback
time with its adaptive power supply approach, enabling very
low supply rails and nearly doubling the power-efficiency
compared to typical Class AB headphone amplifiers.
The LM49251’s no-clip ALC feature prevents distortion
as battery voltages drop, allowing small signals to be amplified
at high gains while preventing clipping of high-level signals.
Its multiple inputs provide configurability for addressing
different system requirements, and the LM49251’s mode
selection, shutdown and volume are controlled through an I2C
compatible interface. The IC’s click-and-pop suppression
eliminates audible transients on power up and during shutdown.
National also introduced the LM49153 mono audio subsystem,
which includes the same features as the LM49251, while integrating
noise gate functionality onto the Class D amplifier. The noise
gate feature prevents noise from being amplified when the
volume is turned up. The LM49153 is offered in a 25-bump,
2.30 mm by 2.42 mm, micro SMD package.
Pricing and Availability
Available now, the LM49251 stereo analog subsystem is priced
at $1.60 each, and the LM49153 mono analog subsystem is priced
at $1.50 each, both in 1,000-unit quantities. For more information
on the LM49251, or to order samples, visit http://www.national.com/pf/LM/LM49251.html.
For more information on the LM49153, or to order samples,