LM4674A Datasheet, PDF (1/18 Pages) National Semiconductor (TI) – Filterless 2.5W Stereo Class D Audio Power Amplifier

September 2006
LM4674A
Filterless 2.5W Stereo Class D Audio Power Amplifier
General Description
The LM4674A is a single supply, high efficiency, 2.5W/
channel, filterless switching audio amplifier. A low noise
PWM architecture eliminates the output filter, reducing ex-
ternal component count, board area consumption, system
cost, and simplifying design.
The LM4674A is designed to meet the demands of mobile
phones and other portable communication devices. Operat-
ing from a single 5V supply, the device is capable of deliv-
ering 2.5W/channel of continuous output power to a 4Ω load
with less than 10% THD+N. Flexible power supply require-
ments allow operation from 2.4V to 5.5V.
The LM4674A features high efficiency compared to conven-
tional Class AB amplifiers. When driving an 8Ω speaker from
a 3.6V supply, the device features 85% efficiency at P_O =
500mW. Four gain options are pin selectable through the
GAIN0 and GAIN1 pins.
Output short circuit protection prevents the device from be-
ing damaged during fault conditions. Superior click and pop
suppression eliminates audible transients on power-up/down
and during shutdown. Independent left/right shutdown con-
trols maximizes power savings in mixed mono/stereo appli-
cations.
Key Specifications
j Efficiency at 3.6V, 100mW into 8Ω
j Efficiency at 3.6V, 500mW into 8Ω
j Efficiency at 5V, 1W into 8Ω
j Quiescent Power Supply Current
at 3.6V supply
j Power Output at V_DD = 5V,
R_L = 4Ω, THD ≤ 10%
j Power Output at V_DD = 5V,
R_L = 8Ω, THD ≤ 10%
j Shutdown current
80% (typ)
85% (typ)
85% (typ)
4mA
2.5W (typ)
1.5W (typ)
0.1µA (typ)
Features
n Output Short Circuit Protection
n Stereo Class D operation
n No output filter required
n Logic selectable gain
n Independent shutdown control
n Minimum external components
n Click and Pop suppression
n Micro-power shutdown
n Available in space-saving 2mm x 2mm x 0.6mm micro
SMD package
Applications
n Mobile phones
n PDAs
n Laptops
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