WM8976 datasheet(21/108 Pages) WOLFSON

21 / 108 page

Pre-Production

WM8976

PP Rev 3.0 April 2006

INPUT SIGNAL PATH

The WM8976 has flexible analogue inputs. An input PGA stage is followed by a boost/mix stage

which drives into the hi-fi ADC. The input path has three input pins which can be configured in a

variety of ways to accommodate single-ended or differential microphones. There is an auxiliary input

pin which can be fed into to the input boost/mix stage as well as driving into the output path. A

bypass path exists from the output of the boost/mix stage into the output left/right mixers.

MICROPHONE INPUTS

The WM8976 can accommodate a variety of microphone configurations including single ended and

differential inputs. The inputs to the differential input PGA are LIN, LIP and L2.

In single-ended microphone input configuration the microphone signal should be input to LIN and the

internal NOR gate configured to clamp the non-inverting input of the input PGA to VMID.

In differential mode the larger signal should be input to LIP or RIP and the smaller (e.g. noisy ground

connections) should be input to LIN or RIN.

Figure 7 Microphone Input PGA Circuit

The input PGA is enabled by the IPPGAENL/R register bits.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

Power

Management

INPPGAENL

Input PGA enable

0 = disabled

1 = enabled

Table 3 Input PGA Enable Register Settings

WM8976 数据表(PDF) 21 Page - Wolfson Microelectronics plc