Pre-Production
WM8904
OUTPUT SIGNAL PATH
The outputs HPOUTL and LINEOUTL are normally derived from the Left DAC output, whilst the
outputs HPOUTR and LINEOUTR are normally derived from the Right DAC output, as illustrated in
Figure 37. A multiplexer is provided on each output path to select the BYPASSL or BYPASSR
analogue input signals in place of the DAC outputs.
A feedback path for common mode noise rejection is provided at HPOUTFB and LINEOUTFB for the
Headphone and Line outputs respectively. This pin must be connected to ground for normal
operation.
Each analogue output can be separately enabled; independent volume control is also provided for
each output. The output signal paths and associated control registers are illustrated in Figure 37. See
“Analogue Outputs” for details of the external connections to these outputs.
HPOUTL_MUTE
HPOUT_VU
HPOUTLZC
HPOUTL_VOL
(-57dB to +6dB, 1 dB steps)
M
U
X
BYPASSL
HPOUTL
HPOUTFB
HPOUTR
HPL_PGA_ENA
HPL_BYP_ENA
M
U
X
DAC L
HPR_PGA_ENA
HPOUTR_MUTE
HPOUT_VU
HPR_BYP_ENA
HPOUTRZC
HPOUTR_VOL
(-57dB to +6dB, 1 dB steps)
LINEOUTL_MUTE
LINEOUT_VU
LINEOUTLZC
LINEOUTL_VOL
(-57dB to +6dB, 1 dB steps)
M
U
X
DAC R
LINEOUTL
LINEOUTFB
LINEOUTR
LINEOUTL_PGA_ENA
LINEOUTL_BYP_ENA
M
U
X
BYPASSR
LINEOUTR_PGA_ENA
LINEOUTR_MUTE
LINEOUT_VU
LINEOUTR_BYP_ENA
LINEOUTRZC
LINEOUTR_VOL
(-57dB to +6dB, 1 dB steps)
AVDD
DCVDD
DC
Servo
HPOUT and LINEOUT
drivers
CHARGE PUMP
Figure 37 Output Signal Path and Control Registers
PP, Rev 3.3, September 2012
71
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
