WM8281ECSSLASHR datasheet(180/392 Pages) CIRRUS

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WM8281

180

Rev 4.0

OUTPUT SIGNAL PATH

The WM8281 provides six stereo pairs of audio output signal paths. These outputs comprise ground-

referenced headphone drivers, differential speaker drivers and digital output interfaces suitable for

external speaker drivers. The output signal paths are summarised in Table 60.

SIGNAL PATH

DESCRIPTIONS

OUTPUT PINS

OUT1L, OUT1R

Ground-referenced headphone output

HPOUT1L, HPOUT1R

OUT2L, OUT2R

Ground-referenced headphone output

HPOUT2L, HPOUT2R

OUT3L, OUT3R

Ground-referenced headphone output

HPOUT3L, HPOUT3R

OUT4L, OUT4R

Differential speaker output

SPKOUTLN, SPKOUTLP,

SPKOUTRP, SPKOUTRN

OUT5L, OUT5R

Digital speaker (PDM) output

SPKDAT1, SPKCLK1

OUT6L, OUT6R

Digital speaker (PDM) output

SPKDAT2, SPKCLK2

Table 60 Output Signal Path Summary

The analogue output paths incorporate high performance 24-bit sigma-delta DACs.

Under default conditions, the headphone drivers provide a stereo, single-ended output. A mono mode

is also available on each headphone output pair, providing a differential (BTL) configuration. The

ground-referenced headphone output paths incorporate a common mode feedback path for rejection

of system-related noise. These outputs support direct connection to headphone loads, with no

requirement for AC coupling capacitors.

The speaker output paths are configured to drive a stereo pair of differential (BTL) outputs. The Class

D design offers high efficiency at large signal levels. With a suitable choice of external speaker, the

Class D output can drive loudspeakers directly, without any additional filter components.

The digital output paths provide two stereo Pulse Density Modulation (PDM) output interfaces, for

connection to external audio devices. A total of four digital output channels are provided.

Digital volume control is available on all outputs (analogue and digital), with programmable ramp

control for smooth, glitch-free operation. A configurable noise gate function is available on each of the

output signal paths. Any of the output signal paths may be selected as input to the Acoustic Echo

Cancellation (AEC) loopback path.

The WM8281 incorporates thermal protection functions, and also provides short-circuit detection on

the Class D speaker and headphone output paths. For further details, refer to the “Thermal Shutdown

and Short Circuit Protection

” section.

The WM8281 output signal paths are illustrated in Figure 56. Note that a phase inversion is present in

the Class D output (OUT4) path, as shown below.

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