WM8737 datasheet(16/38 Pages) WOLFSON

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WM8737L

Preliminary Technical Data

AI Rev 3.0 May 2004

The user can also adjust the microphone preamplifier bias settings to optimise THD+N versus supply

current consumption for their application. Default is full bias for best THD+N performance, but the

user can reduce the bias to 75%, 50% or 25% of default by programming MBCTRL[1:0] in register

R9.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

RBYPEN

Right channel bypass enable

0: Bypass switch is always open.

RINPUT1/2/3 high-impedance biased to

AVDD/2. RPGA input is RACIN pin.

1: Close bypass switch when right mic

preamp is disabled.

LBYPEN

Left channel bypass enable

0: Bypass switch is always open.

LINPUT1/2/3 high-impedance biased to

AVDD/2. LPGA input is LACIN pin.

1: Close bypass switch when left mic

preamp is disabled.

R9 (09h)

Microphone

Preamplifiers

Control

1:0

MBCTRL[1:0]

Bias control for left and right

microphone preamplifiers

00: bias 25%

01: bias 50%

10: bias 75%

11: nominal (100%) bias

Table 4 Microphone Preamplifier Control

MONO-MIXING

The WM8737L can operate as a stereo or mono device, or the two channels can be mixed to mono

in either the analogue domain (before the ADC) or in the digital domain (after the ADC). In all mono

and mono-mix modes unused circuitry can be switched off to save power (see “Power Management”

section). 3D stereo enhancement (See “3D Stereo Enhancement” section) is automatically disabled

in all mono and mono-mix modes.

In analogue mono-mix mode, the signals are mixed in the Left ADC and the Right ADC automatically

switches to dc measurement mode on pin RINPUT1. If dc measurement mode is not required then

the Right ADC can be powered down by setting bit 2 (ADCR) in the power management register R6.

Note that the high pass filter must be disabled if d.c. measurements are required.

In stereo and mono modes the Left/Right ADC data appear at the corresponding Left/Right Channel

outputs. In digital mono-mix mode the mixed data appears on both the Left and Right Channel

outputs. In analogue mono-mix mode the MONOUT bit controls whether the Right channel output

presents the data from the Right ADC (dc measurement) or a copy of the Left Channel (mixed)

output.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R5 (05h)

ADC Control

8:7

MONOMIX[1:0]

00: Stereo

01: Analogue Mono-mix

10: Digital Mono-mix

11: Reserved

R5 (05h)

ADC Control

MONOUT

Analogue mono-mix format control

0: Left ADC data appears on Left

Channel output and Right ADC data

appears on Right Channel Output.

1: Left ADC data appears on both Left

and Right channel outputs.

Table 5 Mono Mixing Control

Note: In stereo mode (R5) 00, Bit 1 must always be set to 0.

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