General Description
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General Description
The Texas Instruments LM48511 integrates a boost converter with a high efficiency Class D audio power
amplifier to provide 3W continuous power into an 8
Ω
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
8
Ω
load with less than 1% distortion (THD+N). The Class D amplifier features a low noise PWM
architecture that eliminates the output filter, reducing external component count, board area consumption,
system cost, and simplifying design. A selectable spread spectrum modulation scheme suppresses 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 selectable feedback networks allow
the LM48511 regulator to dynamically switch between two different output voltages, improving 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 boosted 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 overload protection prevent the device
from damage during fault conditions. Superior click and pop suppression eliminates audible transients
during power-up and shutdown.
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Board Features
The LM48511SQ 3W, Ultra-Low EMI, Filterless, Mono, Class D Audio Power Amplifier with Spread
Spectrum demonstration board has all of the necessary connections using 0.100” headers connectors to
apply the power supply voltage, audio input signals, and audio output (speaker). The amplified audio
signal is only available on the audio output header.
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Operating Conditions
Temperature Range:
T
MIN
≤
T
A
≤
T
MAX
–40°C
≤
T
A
≤
+85°C
Supply Voltage (V
DD
)
3.0V
≤
V
DD
≤
±5.5V
Amplifier Voltage (PV1, V1)
4.8V
≤
PV
1
≤
±8.0V
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AN-1922 LM48511 Evaluation Board
SNAA064C – November 2008 – Revised May 2013
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