WM8971LEFLSLASHR datasheet(53/56 Pages) WOLFSON

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Advanced Information

WM8971L

AI Rev 3.0 March 2004

COMPONENT

REFERENCE

SUGGESTED

VALUE

DESCRIPTION

C1 – C4

100nF

De-coupling for DBVDD, DCVDD, AVDD, HPVDD

C5 – C6

10uF

Reservoir capacitor for DVDD, AVDD. Should the supplies use separate sources then

additional capacitors will be required of each additional source.

C7 – C9

1uF

AC input coupling capacitors

C13

2.2uF

Output AC coupling capacitors to remove DC level from MONOOUT

C14 and C15

220uF

Output AC coupling capacitors to remove DC level from headphone output (If used as

a line-out only, use 2.2uF caps)

C16

100nF

De-coupling for VMID.

C17

10uF

Reservoir capacitor for VMID

C18

100nF

De-coupling for VREF

C19

10uF

Reservoir capacitor for VREF

C20

100nF

De-coupling for MICBIAS – Not required if MICBIAS output is not used

C21

10uF

Reservoir capacitor for MICBIAS – Not required if MICBIAS output is not used

Table 40 External Components Descriptions

Note:

For Capacitors C5, C6, C17, C19 and C21 it is recommended that very low ESR components are used.

LINE INPUT CONFIGURATION

When LINPUT1/RINPUT1 or MIC are used as line inputs, the microphone boost and ALC functions

should normally be disabled.

In order to avoid clipping, the user must ensure that the input signal does not exceed AVDD. This

may require a potential divider circuit in some applications. It is also recommended to remove RF

interference picked up on any cables using a simple first-order RC filter, as high-frequency

components in the input signal may otherwise cause aliasing distortion in the audio band. AC signals

with no DC bias should be fed to the WM8971L through a DC blocking capacitor, e.g. 1

µF.

MICROPHONE INPUT CONFIGURATION

Figure 47 Recommended Circuit for Line Input

For interfacing to a microphone, the ALC function should be enabled and the microphone boost

switched on. Microphones held close to a speaker’s mouth would normally use the 13dB gain setting,

while tabletop or room microphones would need a 29dB boost.

The recommended application circuit is shown above. R1 and R2 form part of the biasing network

(refer to Microphone Bias section). R1 connected to MICBIAS is necessary only for electret type

microphones that require a voltage bias. R2 should always be present to prevent the microphone

47kOhm

220pF

1uF

AGND

L/RINPUT1

MIC

FROM

MICROPHONE

680 Ohm to 2.2kOhm

check microphone's specification

MICBIAS

WM8971LEFL/R 数据表(PDF) 53 Page - Wolfson Microelectronics plc

WM8971LEFL/R 数据表(HTML) 53 Page - Wolfson Microelectronics plc

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WM8971LEFL/R 数据表(PDF) 53 Page - Wolfson Microelectronics plc

WM8971LEFL/R 数据表(HTML) 53 Page - Wolfson Microelectronics plc

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