WM8955BLGECOSLASHV datasheet(34/44 Pages) WOLFSON

34 / 44 page

WM8955BL

Production Data

PD Rev 4.1 February 2007

Figure 19 2-Wire Serial Control Interface

The WM8955BL has two possible device addresses, which can be selected using the CSB pin.

CSB STATE

DEVICE ADDRESS

Low

0011010

High

0011011

Table 25 2-Wire MPU Interface Address Selection

POWER SUPPLIES

The WM8955BL can use up to four separate power supplies:

•

AVDD / AGND: Analogue supply, powers all analogue functions except the headphone drivers.

AVDD can range from 1.8V to 3.6V and has the most significant impact on overall power

consumption (except for power consumed in the headphone). A large AVDD slightly improves

audio quality.

•

HPVDD / HPGND: Headphone supply, powers the headphone drivers. HPVDD is normally tied

to AVDD, but it requires separate layout and decoupling capacitors to curb harmonic distortion.

If HPVDD is lower than AVDD, the output signal may be clipped.

•

DCVDD: Digital core supply, powers all digital functions except the audio and control interfaces.

DCVDD can range from 1.42V to 3.6V, and has no effect on audio quality. The return path for

DCVDD is DGND, which is shared with DBVDD.

•

DBVDD: Digital buffer supply, powers the audio and control interface buffers. This makes it

possible to run the digital core at very low voltages, saving power, while interfacing to other

digital devices using a higher voltage. DBVDD draws much less power than DCVDD, and has

no effect on audio quality. The return path for DBVDD is DGND, which is shared with DCVDD.

It is possible to use the same supply voltage on all four. However, digital and analogue supplies

should be routed and decoupled separately to keep digital switching noise out of the analogue signal

paths.

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