LM4911 Datasheet, PDF (1/22 Pages) National Semiconductor (TI) – Stereo 40mW Low Noise Headphone Amplifier with Selectable Capacitive Coupled or OCL Output

February 2003
LM4911
Stereo 40mW Low Noise Headphone Amplifier with
Selectable Capacitive Coupled or OCL Output
General Description
The LM4911 is an stereo audio power amplifier capable of
delivering 40mW per channel of continuous average power
into a 16Ω load or 25mW per channel into a 32Ω load at 1%
THD+N from a 3V power supply.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. Since the LM4911 does not require
bootstrap capacitors or snubber networks, it is optimally
suited for low-power portable systems. In addition, the
LM4911 may be configured for either single-ended capaci-
tively coupled outputs or for OCL outputs (patent pending).
The LM4911 features a low-power consumption shutdown
mode and a power mute mode that allows for faster turn on
time with less than 1mV voltage change at outputs on re-
lease. Additionally, the LM4911 features an internal thermal
shutdown protection mechanism.
The LM4911 is unity gain stable and may be configured with
external gain-setting resistors.
Key Specifications
n PSRR at 217Hz and 1kHz
65dB (typ)
n Output Power at 1kHz with V_DD = 2.4V, 1% THD+N into
a 16Ω load
25mW (typ)
n Output Power at 1kHz with V_DD = 3V, 1% THD+N into a
16Ω load
40mW (typ)
n Shutdown Current
2.0µA (max)
n Output Voltage change on release from Shutdown
V_DD = 2.4V, R_L = 16Ω (C-Coupled)
1mV (max)
n Mute Current
100µA (max)
Features
n OCL or capacitively coupled outputs (patent pending)
n External gain-setting capability
n Available in space-saving MSOP and LD packages
n Ultra low current shutdown mode
n Mute mode allows fast turn-on (1ms) with less than 1mV
change on outputs
n 2V - 5.5V operation
n Ultra low noise
Applications
n Portable CD players
n PDAs
n Portable electronics devices
Block Diagram
FIGURE 1. Block Diagram
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