1FEATURES
2• Available in Space-Saving WSON and SOIC
Packages
• Ultra Low Current Shutdown Mode
• Can Drive Capacitive Loads up to 500pF
• Improved Click and Pop Circuitry Reduces
Noises During Turn-On and Turn-Off
Transitions
• 2.2 - 5.5V Operation
• No Output Coupling Capacitors, Snubber
Networks, Bootstrap Capacitors or Gain-
Setting Resistors Required
• Unity-Gain Stable

APPLICATIONS
• Wireless and Cellular Handsets
• PDAs
• Portable Computers
• Desktop Computers

KEY SPECIFICATIONS
• Improved PSRR at 217kHz and 1kHz: 64 dB
(typ)
• PO at VDD = 5.0V, 10% THD, 1kHz
– LM4991LD (only), 3Ω, 4Ω: 3W (typ), 2.5 W
(typ)
– All packages, 8Ω load: 1.5 W (typ)
• Shutdown current: 0.1μA (typ)

DESCRIPTION
The LM4991 is a mono bridged audio power amplifier
capable of delivering 3W of continuous average
power into a 3Ω load with less than 10% THD when
powered by a 5V power supply (see Note below). To
conserve power in portable applications, the
LM4991's micropower shutdown mode (ISD = 0.1μA,
typ) is activated when VDD is applied to the
SHUTDOWN pin.
Boomer audio power amplifiers are designed
specifically to provide high power, high fidelity audio output. They require few external components and
operate on low supply voltages from 2.2V to 5.5V.
Since the LM4991 does not require output coupling
capacitors, bootstrap capacitors, or snubber
networks, it is ideally suited for low-power portable
systems that require minimum volume and weight.
Additional LM4991 features include thermal shutdown
protection, unity-gain stability, and external gain set.
Note: An LM4991LD that has been properly mounted
to a circuit board will deliver 3W into 3Ω (at 10% THD). The other package options for the LM4991 will
deliver 1.5W into 8Ω (at 10% THD). See the
Application Information sections for further
information concerning the LM4991LD and
LM4991M.