WM8959 datasheet(69/155 Pages) WOLFSON

69 / 155 page

Pre-Production

WM8959

PP, May 2008, Rev 3.1

When driving a handset ear speaker using OUT3 and OUT4 from LOMIX and ROMIX, the required

phase difference may be provided by inverting one of the DAC outputs. Alternatively, the phase

difference can be achieved by mixing Left and Right channels through LOMIX to OUT3 and by

muting OUT4. Similarly, the phase difference can be achieved by mixing Left and Right channels

through ROMIX to OUT4 and by muting OUT3.

Note that a differential output will provide an additional 6dB gain at the output pins. Register bits

OUT3ATTN and OUT4ATTN can be used to compensate for this gain if required.

Fully differential headphone drive is possible between LOUT and OUT3 and between ROUT and

OUT4. Routing LOPGA to OUT3 and ROPGA to OUT4 results in a phase inversion at LOUT with

respect to OUT3 and at ROUT with respect to OUT4. This allows fully differential headset drive, with

greatly improved crosstalk performance, improved bass response, increased noise immunity and

removing the need for large and expensive DC-blocking capacitors.

To ensure fully balanced differential operation, LOUT and OUT3 must be set to the same gain as

each other, and ROUT and OUT4 must be set to the same gain as each other. This is best achieved

by setting OUT3ATTN and OUT4ATTN to 0dB, whilst setting volume controls LOPGAVOL and

LOUTVOL at matching levels and setting volume controls ROPGAVOL and ROUTVOL at matching

levels.

Some example headphone output configurations are shown below.

Figure 31 AC-Coupled Headphone Drive

Figure 32 Capless Mode Headphone Drive

Figure 33 Headphone and Ear Speaker Drive

Figure 34 Fully Differential Headphone Drive

LINE OUTPUT CONFIGURATIONS

The line outputs LON, LOP, RON and ROP are each driven by different output mixers as described

below.

The LOP and ROP pins output a mix of LIN12 input PGA, RIN12 input PGA and either LOMIX or

ROMIX outputs.

The LON output is a mix of ROMIX, LOMIX and a phase-inverted copy of LOP.

The RON output is a mix of LOMIX, ROMIX and a phase-inverted copy of ROP.

Volume control of LOMIX and ROMIX is available in all cases above via LOPGA and ROPGA. An

additional -6dB attenuation option is provided on LOP and ROP outputs.

WM8959 Datasheet(PDF) 69 Page - Wolfson Microelectronics plc