LM4550B National Semiconductor Corporation, LM4550B Datasheet - Page 9

• Manufacturer Part Number: LM4550B
• Description: Ac 97 Rev 2.1 Multi-channel Audio Codec With Stereo Headphone Amplifier, Sample Rate Conversion And National 3d Sound
• Manufacturer: National Semiconductor Corporation

Connection Diagram
Pin Descriptions
PC_BEEP
PHONE
Name
Pin
12
13
I / O
I
I
Functional Description
Mono Input
This line level (1 Vrms nominal) mono input is mixed equally into both channels of the Stereo
Mix signal at MIX2 under the control of the PC_Beep Volume control register, 0Ah. The
PC_BEEP level can be muted or adjusted from 0 dB to -45 dB in 3 dB steps. The Stereo Mix
signal feeds both the Line Out and Headphone Out analog outputs and is also selectable at
the Record Select Mux. During Initialization or Cold Reset, (reset pin held active low),
PC_BEEP is switched directly to both channels of the Line Out stereo output, bypassing all
volume controls. This allows signals such as PC power-on self-test tones to be heard through
the PC’s audio system before the codec registers are configured.
Mono Input
This line level (1 Vrms nominal) mono input is selectable at the Record Select Mux for
conversion by either or both channels of the stereo ADC. It can also be mixed equally into
both channels of the Stereo Mix signal at MIX2 under the control of the Phone Volume
register, 0Ch. The PHONE level can be muted or adjusted from +12 dB to -34.5 dB in 1.5 dB
steps. The Stereo Mix signal feeds both the Line Out and Headphone Out analog stereo
outputs and is also selectable at the Record Select Mux.
See NS Package Number VBH48A
Order Number LM4550BVH
ANALOG I/O
Top View
9
20123702
www.national.com