LM4868 Datasheet, PDF (1/28 Pages) National Semiconductor (TI) – Output-Transient-Free Dual 2.1W Audio Amplifier Plus No Coupling Capacitor Stereo Headphone Function

August 2002
LM4868
Output-Transient-Free Dual 2.1W Audio Amplifier Plus
No Coupling Capacitor Stereo Headphone Function
General Description
The LM4868 is a dual bridge-connected audio power ampli-
fier which, when connected to a 5V supply, will deliver 2.1W
to a 4Ω load (Note 1) or 2.4W to a 3Ω load (Note 2) with less
than 1.0% THD+N. The LM4868 uses advanced, latest gen-
eration circuitry to eliminate all traces of clicks and pops
when the supply voltage is first applied. The amplifier has a
headphone-amplifier-select input pin. It is used to switch the
amplifiers from bridge to single-ended mode for driving
headphones. A new circuit topology eliminates headphone
output coupling capacitors (patent pending). A MUX control
pin allows selection between the two sets of stereo input
signals. The MUX control can also be used to select be-
tween two different customer-specified closed-loop re-
sponses.
Boomer audio power amplifiers are designed specifically to
provide high quality output power from a surface mount
package and require few external components. To simplify
audio system design, the LM4868 combines dual bridge
speaker amplifiers and stereo headphone amplifiers in one
package.
The LM4868 features an externally controlled power-saving
micropower shutdown mode, a stereo headphone amplifier
mode, and thermal shutdown protection.
Note 1: An LM4868LQ or LM4868MTE that has been properly mounted to
a circuit board will deliver 2.1W into 4Ω. The Mux control can also be used to
select two different closed-loop responses. LM4868MT will deliver 1.1W into
8Ω. See the Application Information sections for further information concern-
ing the LM4868LQ and the LM4868MT.
Note 2: An LM4868LQ or LM4868MTE that has been properly mounted to a
circuit board and forced-air cooled will deliver 2.4W into 3Ω.
Key Specifications
n P_O at 1% THD+N
n LM4868LQ, 3Ω load
2.4W (typ)
n LM4868LQ, 4Ω load
2.1W (typ)
n LM4868MTE, 4Ω
1.9W (typ)
n LM4868MT, 8Ω
1.1W (typ)
n Single-ended mode - THD+N at 75mW into 32Ω 0.5%
(max)
n Shutdown current
0.7µA (typ)
Features
n Advanced “click and pop” suppression circuitry
n Eliminates headphone amplifier output coupling
capacitors (patent pending)
n Stereo headphone amplifier mode
n Input mux control and two separate inputs per channel
n Thermal shutdown protection circuitry
n LLP, TSSOP, and exposed-DAP TSSOP packaging
available
Applications
n Multimedia monitors
n Portable and desktop computers
n Portable audio systems
Connection Diagrams
20026758
Top View
Order Number LM4868MT, LM4868MTE
See NS Package Number MTC20 for TSSOP
See NS Package Number MXA20A for Exposed-DAP TSSOP
Boomer^® is a registered trademark of National Semiconductor Corporation.
© 2002 National Semiconductor Corporation DS200267
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