Pre-Production
WM8959
ANALOGUE OUTPUTS
The speaker, headphone and line outputs are highly configurable and may be used in many different
ways.
SPEAKER OUTPUT CONFIGURATIONS
The speaker outputs SPKP and SPKN are driven by the speaker mixer SPKMIX, and speaker
volume control SPKPGA, which can output a mix that is any combination of the following signals:
•
•
•
•
Left DAC and Right DAC outputs
LOMIX and ROMIX outputs via volume controls LOPGA and ROPGA
Line inputs LIN2 and RIN2
Output from left and right input mixers (AINLMUX & AINRMUX)
The speaker mixer is controlled as described under “Output Signal Path”. The speaker mixer output
can be attenuated to avoid clipping when mixing multiple signal inputs. Fine adjustment of the
speaker output can be made by the speaker volume control SPKPGA.
The speaker outputs SPKP and SPKN operate in a BTL configuration in Class AB and Class D
amplifier modes. The mode is selected by register bit CDMODE. The outputs are capable of driving
1W into an 8Ω BTL load (or 500mW in class AB mode for thermal reasons) at room temperature. For
performance at higher temperatures, see Error! Reference source not found. in the
“Recommended Operating Conditions” section. Ultra-low leakage and high PSRR allow the speaker
supply SPKVDD to be directly connected to a lithium battery.
Six levels of AC and DC signal boost are provided in order to deliver maximum output power for
many commonly-used SPKVDD/AVDD combinations. These boost options are available in both
Class AB and Class D modes. The AC and DC gain levels from 1.0x to 1.8x are selected using
register bits ACGAIN and DCGAIN. To prevent pop noise, DCGAIN and ACGAIN should not be
modified while the speaker outputs are enabled.
Note that an appropriate SPKVDD supply voltage must be provided to prevent waveform clipping
when speaker boost is used.
AVDD
SPKVDD
DCGAIN[2:0]
SPKATTN[1:0]
SPKVOL[6:0]
ACGAIN[2:0]
SPKP
SPKN
SPEAKER MIXER
BTL Connection
provides an
additional 6dB gain
SPKGND
AGND
DCGAIN[2:0] or ACGAIN[2:0]
SPKVDD
000 = 1.00x
001 = 1.27x
010 = 1.40x
011 = 1.52x
100 = 1.67x
101 = 1.80x
Signal x ACGAIN
AVDD
VMID
VMID x DCGAIN
VMID x DCGAIN
AGND
Figure 30 Speaker Boost Operation
PP, May 2008, Rev 3.1
67
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
