Rev 1.03 architecture. Using 18-Bit
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A/D and D/A convert-
ers, the LM4540 provides 90dB of dynamic range.
The LM4540 was designed specifically to provide a high
quality audio path and provide all analog functionality in a PC
audio system. It features full duplex stereo A/D鈥檚 and D/A鈥檚
and an analog mixer with 2 stereo and 3 mono inputs, each
of which has separate gain, attenuation and mute control. In
addition, the LM4540 provides National鈥檚 3D Sound stereo
enhancement technology.
The LM4540 features AC-Link, a synchronous, fixed rate se-
rial bus for connection to the digital AC 鈥?7 Controller. The
separation of the analog and digital functions of the AC 鈥?7
architecture allows for system design flexibility and in-
creased overall performance.
Key Specifications
n
Analog Mixer Dynamic Range
n
D/A Dynamic Range
n
A/D Dynamic Range
95dB (typ)
89dB (typ)
90dB (typ)
Features
n
Audio Codec 鈥?7 compliant
n
Stereo 18-Bit
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A/D鈥檚 and D/A鈥檚 with 128X
oversampling
n
National鈥檚 3D Sound circuitry
n
Power management support
n
Digital Interface 3V and 5V compliant
Applications
n
PC Audio Systems Requiring Only 2 Stereo Inputs (CD,
Line) and 3 Mono Inputs (Mic, Phone, PC Beep)
Block Diagram
DS100906-1
FIGURE 1. LM4540 Block Diagram
漏 1999 National Semiconductor Corporation
DS100906
www.national.com
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