Datasheet

LM4549B
www.ti.com SNAS598A –JULY 2012–REVISED MAY 2013
ANALOG I/O (continued)
Name Pin I / O Functional Description
Left Stereo Channel Input
This line level input (1 Vrms nominal) is selectable at the left channel of the stereo Record Select Mux
for conversion by the left channel ADC. It can also be mixed into the left channel of the Stereo Mix 3D
VIDEO_L 16 I signal at MIX1 under the control of the Video Volume register, 14h. The VIDEO_L level can be muted
(along with VIDEO_R) or adjusted from +12 dB to -34.5 dB in 1.5 dB steps. Stereo Mix 3D is
combined into the Stereo Mix signal at MIX2 for access to the stereo outputs Line Out and Line Level
Out.
Right Stereo Channel Input
This line level input (1 Vrms nominal) is selectable at the right channel of the stereo Record Select
Mux for conversion by the right channel ADC. It can also be mixed into the right channel of the Stereo
VIDEO_R 17 I Mix 3D signal at MIX1 under the control of the Video Volume register, 14h. The VIDEO_R level can be
muted (along with VIDEO_L) or adjusted from +12 dB to -34.5 dB in 1.5 dB steps. Stereo Mix 3D is
combined into the Stereo Mix signal at MIX2 for access to the stereo outputs Line Out and Line Level
Out.
Left Stereo Channel Input
This line level input (1 Vrms nominal) is selectable at the left channel of the stereo Input Mux for
conversion by the left channel ADC. It can also be mixed into the left channel of the Stereo Mix 3D
CD_L 18 I
signal at MIX1 under the control of the CD Volume register, 12h. The CD_L level can be muted (along
with CD_R) or adjusted from +12 dB to -34.5 dB in 1.5 dB steps. Stereo Mix 3D is mixed into the
Stereo Mix signal at MIX2 for access to the stereo outputs Line Out and Line Level Out.
AC Ground Reference
This input is the reference for the signals on both CD_L and CD_R. CD_GND is not a DC ground and
should be AC-coupled to the stereo source ground common to both CD_L and CD_R. The three
CD_GND 19 I inputs, CD_GND, CD_L and CD_R act together as a quasi-differential stereo input with CD_GND
providing AC common-mode feedback to reject ground noise. This can improve the input SNR for a
stereo source with a good common ground but precision resistors may be needed in any external
attenuators to achieve the necessary balance between the two channels.
Right Stereo Channel Input
This line level input (1 Vrms nominal) is selectable at the right channel of the stereo Input Mux for
conversion by the right channel ADC. It can also be mixed into the right channel of the Stereo Mix 3D
CD_R 20 I
signal at MIX1 under the control of the CD Volume register, 12h. The CD_R level can be muted (along
with CD_L) or adjusted from +12 dB to -34.5 dB in 1.5 dB steps. Stereo Mix 3D is combined into the
Stereo Mix signal at MIX2 for access to the stereo outputs Line Out and Line Level Out.
Mono microphone input
Either MIC1 or MIC2 can be muxed to a programmable boost amplifier with selection by the MS bit (bit
D8) in the General Purpose register, 20h. The boost amplifier gain (0 dB or 20 dB) is set by the 20dB
bit (D6) in the Mic Volume register, 0Eh. Nominal input levels at the two gain settings are 1 Vrms and
0.1 Vrms respectively. The amplifier output is selectable (Record Select register, 1Ah) by either the
MIC1 21 I
right or left channels of the Record Select Mux for conversion on either or both channels of the stereo
ADCs. The amplifier output can also be accessed at the stereo mixer MIX1 (muting and mixing
adjustments via Mic Volume register, 0Eh) where it is mixed equally into both left and right channels of
Stereo Mix 3D for access to the stereo outputs Line Out and Line Level Out. Access to the Mono
analog output is selected by a mux controlled by the MIX bit (D9) in General Purpose register, 20h.
Mono microphone input
Either MIC1 or MIC2 can be muxed to a programmable boost amplifier with selection by the MS bit (bit
D8) in the General Purpose register, 20h. The boost amplifier gain (0 dB or 20 dB) is set by the 20dB
bit (D6) in the Mic Volume register, 0Eh. Nominal input levels at the two gain settings are 1 Vrms and
0.1 Vrms respectively. The amplifier output is selectable (Record Select register, 1Ah) by either the
MIC2 22 I
right or left channels of the Record Select Mux for conversion on either or both channels of the stereo
ADCs. The amplifier output can also be accessed at the stereo mixer MIX1 (muting and mixing
adjustments via Mic Volume register, 0Eh) where it is mixed equally into both left and right channels of
Stereo Mix 3D for access to the stereo outputs Line Out and Line Level Out. Access to the Mono
analog output is selected by a mux controlled by the MIX bit (D9) in General Purpose register, 20h.
Left Stereo Channel Input
This line level input (1 Vrms nominal) is selectable at the left channel of the stereo Record Select Mux
for conversion by the left channel ADC. It can also be mixed into the left channel of the Stereo Mix 3D
LINE_IN_L 23 I signal at MIX1 under the control of the Line In Volume register, 10h. The LINE_IN_L level can be
muted (along with LINE_IN_R) or adjusted from +12 dB to -34.5 dB in 1.5 dB steps. Stereo Mix 3D is
combined into the Stereo Mix signal at MIX2 for access to the stereo outputs Line Out and Line Level
Out.
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