LM48511 Datasheet, PDF (1/22 Pages) National Semiconductor (TI) – 3W, Ultra-Low EMI, Filterless, Mono, Class D Audio Power Amplifier with Spread Spectrum

September 2007
LM48511
3W, Ultra-Low EMI, Filterless, Mono, Class D Audio Power
Amplifier with Spread Spectrum
General Description
The LM48511 integrates a boost converter with a high effi-
ciency Class D audio power amplifier to provide 3W continu-
ous power into an 8Ω speaker when operating from a 5V
power supply. When operating from a 3V to 4V power supply,
the LM48511 can be configured to drive 1 to 2.5W into an
8Ω load with less than 1% distortion (THD+N). The Class D
amplifier features a low noise PWM architecture that elimi-
nates the output filter, reducing external component count,
board area consumption, system cost, and simplifying design.
A selectable spread spectrum modulation scheme suppress-
es RF emissions, further reducing the need for output filters.
The LM48511’s switching regulator is a current-mode boost
converter operating at a fixed frequency of 1MHz. Two se-
lectable feedback networks allow the LM48511 regulator to
dynamically switch between two different output voltages, im-
proving efficiency by optimizing the amplifier’s supply voltage
based on battery voltage and output power requirements.
The LM48511 is designed for use in portable devices, such
as GPS, mobile phones, and MP3 players. The high, 80%
efficiency at 5V, extends battery life when compared to Boost-
ed Class AB amplifiers. Independent regulator and amplifier
shutdown controls optimize power savings by disabling the
regulator when high output power is not required.
The gain of the LM48511 is set by external resistors, which
allows independent gain control from multiple sources by
summing the signals. Output short circuit and thermal over-
load protection prevent the device from damage during fault
conditions. Superior click and pop suppression eliminates au-
dible transients during power-up and shutdown.
Key Specifications
■ Quiescent Power Supply Current
V_DD = 3V
V_DD = 5V
■ P_O at V_DD = 5V, PV1 = 7.8V
R_L = 8Ω, THD+N = 1%
■ P_O at V_DD = 3V, PV1 = 4.8V
R_L = 8Ω, THD+N = 1%
■ Shutdown Current at V_DD = 3V
9mA (typ)
13.5mA (typ)
3.0W (typ)
1W (typ)
0.01μA (typ)
Features
■ ^{3W Output into 8Ω at 5V with THD+N = 1%}
■ ^{Selectable spread spectrum mode reduces EMI}
■ ^{80% Efficiency}
■ ^{Independent Regulator and Amplifier Shutdown Controls}
■ ^{Dynamically Selectable Regulator Output Voltages}
■ ^{Filterless Class D}
■ ^{3.0V – 5.5V operation}
■ ^{Low Shutdown Current}
■ ^{Click and Pop Suppression}
Applications
■ ^GPS
■ ^{Portable media}
■ ^Cameras
■ ^{Mobile Phones}
■ ^{Handheld games}
EMI Graph
300222h5
FIGURE 1. LM48511 RF Emissions — 3 inch cable
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