WM8993 datasheet(92/229 Pages) WOLFSON

92 / 229 page

WM8993

Production Data

PD, November 2010, Rev 4.0

Eight levels of AC signal boost are provided in order to deliver maximum output power for many

commonly-used SPKVDD/AVDD1 combinations. These boost options are available in both Class AB

and Class D modes. The AC boost levels from 0dB to +12dB are selected using register bits

SPKOUTL_BOOST and SPKOUTR_BOOST. To prevent pop noise, SPKOUTL_BOOST and

SPKOUTR_BOOST should not be modified while the speaker outputs are enabled. Figure 26

illustrates the speaker outputs and the mixing and gain/boost options available.

Ultra-low leakage and high PSRR allow the speaker supply SPKVDD to be directly connected to a

lithium battery. Note that an appropriate SPKVDD supply voltage must be provided to prevent

waveform clipping when speaker boost is used.

DC gain is applied automatically in both class AB and class D modes with a shift from VMID to

SPKVDD/2. This provides optimum signal swing for maximum output power. In class AB mode, an

ultra-high PSRR mode is available, in which the DC reference for the speaker driver is fixed at VMID.

This mode is selected by enabling the SPKAB_REF_SEL bit (see Table 60). In this mode, the output

power is limited but the driver will still be capable of driving more than 500mW in 8

Ω while

maintaining excellent suppression of noise on SPKVDD (for example, TDMA noise in a GSM phone

application).

Figure 26 Speaker Output Configuration and AC Boost Operation

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R35 (23h)

SPKMIXR

Attenuation

SPKOUT_CLASSAB

_MODE

Speaker Class AB Mode Enable

0 = Class D mode

1 = Class AB mode

R37 (25h)

SPKOUT

Boost

5:3

SPKOUTL_BOOST

[2:0]

000b

(1.0x)

Left Speaker Gain Boost

000 = 1.00x boost (+0dB)

001 = 1.19x boost (+1.5dB)

010 = 1.41x boost (+3.0dB)

011 = 1.68x boost (+4.5dB)

100 = 2.00x boost (+6.0dB)

101 = 2.37x boost (+7.5dB)

110 = 2.81x boost (+9.0dB)

111 = 3.98x boost (+12.0dB)

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