LM4947 Datasheet, PDF (1/32 Pages) National Semiconductor (TI) – Mono Class D and Stereo Audio Subsystem with OCL Headphone Amplifier and National 3D

October 2006
LM4947
Mono Class D and Stereo Audio Subsystem with OCL
Headphone Amplifier and National 3D
General Description
The LM4947 is an audio subsystem capable of efficiently
delivering 500mW (Class D operation) of continuous aver-
age power into a mono 8Ω bridged-tied load (BTL) with 1%
THD+N, 37mW (Class AB operation) power channel of con-
tinuous average power into stereo 32Ω single-ended (SE)
loads with 1% THD+N, or an output capacitor-less (OCL)
configuration with identical specification as the SE configu-
ration, from a 3.3V power supply.
The LM4947 has six input channels: one pair for a two-
channel stereo signal, the second pair for a secondary two-
channel stereo input, and the third pair for a differential
single-channel mono input. Additionally, the two sets of ste-
reo inputs may be configured as a single stereo differential
input (differential left and differential right). The LM4947
features a 32-step digital volume control and eight distinct
output modes. The digital volume control, 3D enhancement,
and output modes are programmed through a two-wire I²C
compatible interface that allows flexibility in routing and mix-
ing audio channels.
The RF suppression circuitry in the LM4947 makes it well-
suited for GSM mobile phones and other portable applica-
tions in which strong RF signals generated by an antenna
(and long output traces) may couple audibly into the ampli-
fier.
The LM4947 is designed for cellular phones, PDAs, and
other portable handheld applications. It delivers high quality
output power from a surface-mount package and requires
only eight external components in the OCL mode (two addi-
tional components in SE mode).
Key Specifications
j THD+N at 1kHz, 500mW
into 8Ω BTL (3.3V)
j THD+N at 1kHz, 37mW
into 32Ω SE (3.3V)
j Single Supply Operation (V_DD)
j I²C Single Supply Operation
1.0% (typ)
1.0% (typ)
2.7 to 5.5V
2.2 to 5.5V
Features
n I²C Control Interface
n I²C programmable National 3D Audio
n I²C controlled 32 step digital volume control (-59.5dB to
+18dB)
n Three independent volume channels (Left, Right, Mono)
n Eight distinct output modes
n Small, 25–bump micro SMD packaging
n “Click and Pop” suppression circuitry
n Thermal shutdown protection
n Low shutdown current (0.1µA, typ)
n RF suppression
n Differential mono and stereo inputs
n Stereo input mux
Applications
n Mobile Phones
n PDAs
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