WM8994ECSSLASHR datasheet(147/363 Pages) CIRRUS

147 / 363 page

WM8994

Rev 4.6

147

The line outputs incorporate a common mode, or ground loop, feedback path which provides rejection

of system-related ground noise. The return path, via LINEOUTFB, is enabled separately for

LINEOUT1 and LINEOUT2 using the LINEOUT1_FB and LINEOUT2_FB bits as defined in Table 77.

Ground loop feedback is a benefit to single-ended line outputs only; it is not applicable to differential

outputs, which already inherently offer common mode noise rejection.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R55 (0037h)

Additional

Control

LINEOUT1_FB

Enable ground loop noise

feedback on LINEOUT1

0 = Disabled

1 = Enabled

LINEOUT2_FB

Enable ground loop noise

feedback on LINEOUT2

0 = Disabled

1 = Enabled

Table 77 Line Output Ground Loop Feedback Enable

GENERAL PURPOSE INPUT/OUTPUT

The WM8994 provides a number of GPIO functions to enable interfacing and detection of external

hardware and to provide logic outputs to other devices. The input functions can be polled directly or

can be used to generate an Interrupt (IRQ) event. The GPIO and Interrupt circuits support the

following functions:



Alternate interface functions (AIF2, AIF3)



Button detect (GPIO input)



Logic ‘1’ and logic ‘0’ output (GPIO output)



SDOUT (4-wire SPI Control Interface data)



Interrupt (IRQ) status output



Over-Temperature detection



Accessory detection (MICBIAS current detection)



Frequency Locked Loop (FLL) Lock status output



Sample Rate Conversion (SRC) Lock status output



Dynamic Range Control (DRC) Signal activity detection



Control Write Sequencer status output



Digital Core FIFO error status output



Clock output (SYSCLK divided by OPCLK_DIV)



Frequency Locked Loop (FLL) Clock output

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