WM8281ECSSLASHR datasheet(46/392 Pages) CIRRUS

46 / 392 page

WM8281

Rev 4.0

INPUT SIGNAL PATH

The WM8281 has eight highly flexible input channels. Selectable combinations of up to six analogue

(mic or line) or eight digital input configurations are supported.

The analogue input paths support single-ended and differential modes, programmable gain control

and are digitised using a high performance 24-bit sigma-delta ADC.

The digital input paths interface directly with external digital microphones; a separate microphone

interface clock is provided for 4 separate stereo pairs of digital microphones. Digital delay can be

applied to any of the digital input paths; this can be used for phase adjustment of any digital input,

including directional control of multiple microphones.

Three microphone bias (MICBIAS) generators are available, which provide a low noise reference for

biasing electret condenser microphones (ECMs) or for use as a low noise supply for MEMS

microphones and digital microphones.

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

control for smooth, glitch-free operation. Any pair of analogue or digital inputs may be selected as

input to the Ambient Noise Cancellation (ANC) processing function.

The IN1L and IN1R input signal paths and control registers are illustrated in Figure 13. The IN2 and

IN3 signal paths are equivalent to the IN1 signal path. The IN4 signal path supports digital

microphone input only.

IN1L_PGA_VOL [6:0]

ADC

IN1_MODE [1:0]

00 = Differential IN1xP

– IN1xN

01 = Single-ended IN1xP (non-inverting)

10 = Digital Microphone

11 = Reserved

IN1L_ENA

IN1R_ENA

IN1RN/DMICDAT1

IN1RP

ADC

IN1LN/DMICCLK1

IN1LP

IN1R_PGA_VOL [6:0]

IN1_DMIC_SUP [1:0]

IN1L_DMIC_DLY [5:0]

IN1R_DMIC_DLY [5:0]

IN1_OSR

00 = 1.536MHz

01 = 3.072MHz

10 = 6.144MHz

11 = 768kHz

IN1L_VOL [7:0]

IN1R_VOL [7:0]

CLK

DAT

IN1L_HPF

IN1R_HPF

IN_HPF_CUT[2:0]

Digital Mic

Interface

Figure 13 Input Signal Paths

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