LM4941_07 Datasheet, PDF (1/16 Pages) –

March 2007
LM4941 
1.25 Watt Fully Differential Audio Power Amplifier With RF
Suppression and Shutdown
General Description
The LM4941 is a fully differential audio power amplifier pri-
marily designed for demanding applications in mobile phones
and other portable communication device applications. It is
capable of delivering 1.25 watts of continuous average power
to a 8Ω load with less than 1% distortion (THD+N) from a
5V_DC power supply. The LM4941 does not require output
coupling capacitors or bootstrap capacitors, and therefore is
ideally suited for mobile phone and other small form factor
applications where minimal PCB space is a primary require-
ment.
The LM4941 also features proprietary internal circuitry that
suppresses the coupling of RF signals into the chip. This is
important because certain types of RF signals (such as GSM)
can couple into audio amplifiers in such a way that part of the
signal is heard through the speaker. The RF suppression cir-
cuitry in the LM4941 makes it well-suited for portable appli-
cations in which strong RF signals generated by an antenna
from or a cellular phone or other portable electronic device
may couple audibly into the amplifier.
Other features include a low-power consumption shutdown
mode, internal thermal shutdown protection, and advanced
pop & click circuitry.
Key Specifications
■ Improved PSRR at 217Hz
■ Power Output, V_DD = 5.0V,
 R_L = 8Ω, 1% THD+N
■ Power Output, V_DD = 3.0V,
 R_L = 8Ω, 1% THD+N
■ Shutdown Current
95dB (typ)
1.25W (typ)
430mW (typ)
0.1µA (typ)
Features
■ ^{Improved RF suppression, by up to 20dB over previous}
designs in selected applications
■ ^{Fully differential amplification}
■ ^{Available in space-saving micro SMD package}
■ ^{Ultra low current shutdown mode}
■ ^{Can drive capacitive loads up to 100pF}
■ ^{Improved pop & click circuitry eliminates noises during}
turn-on and turn-off transitions
■ ^{2.4 - 5.5V operation}
■ ^{No output coupling capacitors, snubber networks or}
bootstrap capacitors required
Applications
■ ^{Mobile phones}
■ ^PDAs
■ ^{Portable electronic devices}
Typical Application
20170366
FIGURE 1. Typical Audio Amplifier Application Circuit
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation 201703
www.national.com