Pre-Production
WM8904
Up to
4
GPIO pins may be configured for miscellaneous input/output functions such as
button/accessory detect inputs, or for clock, system status, or programmable logic level output for
control of additional external circuitry. Interrupt logic, status readback and de-bouncing options are
supported within this functionality.
ANALOGUE INPUT SIGNAL PATH
The WM8904 has six analogue input pins, which may be used to support connections to multiple
microphone or line input sources. The input multiplexer on the Left and Right channels can be used to
select different configurations for each of the input sources. The analogue input paths can support
line and microphone inputs, in single-ended and differential modes. The input stage can also provide
common mode noise rejection in some configurations.
Two of the six analogue input pins have dual functionality and can be used as digital microphone
inputs. (See the “Digital Microphone Interface” section for details.)
The Left and Right analogue input channels are routed to the Analogue to Digital converters (ADCs).
There is also a bypass path for each channel, enabling the signal to be routed directly to the output
multiplexers and PGAs.
The WM8904 input signal paths and control registers are illustrated in Figure 20.
Figure 20 Block Diagram for Input Signal Path
PP, Rev 3.3, September 2012
35
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
