WM8940
Pre-Production
DESCRIPTION
REGISTER
ADDRESS
BIT
3:0
LABEL
DEFAULT
0000
LIMBOOST
Limiter volume boost (can be used as a
stand alone volume boost when
LIMEN=0):
0000 = 0dB
0001 = +1dB
0010 = +2dB
0011 = +3dB
0100 = +4dB
0101 = +5dB
0110 = +6dB
0111 = +7dB
1000 = +8dB
1001 = +9dB
1010 = +10dB
1011 = +11dB
1100 = +12dB
1101 to 1111 = reserved
Table 33 DAC Digital Limiter Control
ANALOGUE OUTPUTS
The WM8940 has a single MONO output and two outputs SPKOUTP and SPOUTN for driving a
mono BTL speaker. These analogue output stages are supplied from SPKVDD and are capable of
driving up to 1V rms signals.
SPKOUTP/SPKOUTN OUTPUTS
The SPKOUT pins can drive a single bridge tied 8Ω speaker or two headphone loads of 16Ω or 32Ω
or a line output (see Headphone Output and Line Output sections, respectively). The signal to be
output on SKPKOUT comes from the Speaker Mixer circuit and can be any combination of the DAC
output, the Bypass path (output of the boost stage) and the AUX input. The SPKOUTP/N volume is
controlled by the SPKVOL register bits. Note that gains over 0dB may cause clipping if the signal is
large. The SPKMUTE register bit causes the speaker outputs to be muted (the output DC level is
driven out). The output pins remains at the same DC level (VMIDOP), so that no click noise is
produced when muting or un-muting.
The SPKOUTN pin always drives out an inverted version of the SPKOUTP signal.
REGISTER
ADDRESS
BIT
LABEL
AUX2SPK
DEFAULT
DESCRIPTION
R50
5
1
0
Output of auxiliary amplifier to speaker
mixer input
Speaker mixer
control
0 = not selected
1 = selected
BYP2SPK
0
Bypass path (output of input boost
stage) to speaker mixer input
0 = not selected
1 = selected
0
8
DAC2SPK
SPKATTN
0
0
Output of DAC to speaker mixer input
0 = not selected
1 = selected
R54
Attenuation control for bypass path
(output of input boost stage) to speaker
mixer input
Bypass path
attenuation
control
0 = 0dB
1 = -10dB
Table 34 Speaker Mixer Control
Pre-Production, Rev 3.0, February 2007
44
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
