WM8941
Pre Production
AUXILLIARY INPUT
An auxiliary input circuit (Figure 7) is provided which consists of an amplifier which can be configured
either as an inverting buffer for a single input signal or as a mixer/summer for multiple inputs with the
use of external resistors. The circuit is enabled by the register bit AUXEN.
Figure 7 Auxiliary Input Circuit
The AUXMODE register bit controls the auxiliary input mode of operation:
In buffer mode (AUXMODE=0) the switch labelled AUXSW in Figure 7 is open and the signal at the
AUX pin will be buffered and inverted through the aux circuit using only the internal components.
In mixer mode (AUXMODE=1) the on-chip input resistor is bypassed, this allows the user to sum in
multiple inputs with the use of external resistors. When used in this mode there will be gain
variations through this path from part to part due to the variation of the internal 20kΩ resistors
relative to the higher tolerance external resistors.
REGISTER
ADDRESS
BIT
LABEL
AUXEN
DEFAULT
DESCRIPTION
R1
6
3
0
Auxiliary input buffer enable
0 = OFF
Power
management 1
1 = ON
R44
AUXMODE
0
0 = inverting buffer
Input control
1 = mixer (on-chip input resistor bypassed)
Table 5 Auxiliary Input Buffer Control
PP, Rev 3.3, December 2007
22
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
