WM8978GEFLSLASHV datasheet(17/78 Pages) WOLFSON

17 / 78 page

Product Preview

WM8978

PP Rev 1.7 January 2005

INPUT SIGNAL PATH

The WM8978 has a number of flexible analogue inputs. There are two input channels, Left and

Right, each of which consists of an input PGA stage followed by a boost/mix stage which drives into

the hi-fi ADC. Each input path has three input pins which can be configured in a variety of ways to

accommodate single-ended, differential or dual differential microphones.

There are two auxiliary

input pins 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 WM8978 can accommodate a variety of microphone configurations including single ended and

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

right differential input PGA are RIN, RIP and R2.

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

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

Figure 6 Microphone Input PGA Circuit

WM8978GEFL/V Datasheet(PDF) 17 Page - Wolfson Microelectronics plc