wm9081 Wolfson Microelectronics plc, wm9081 Datasheet - Page 51

• Manufacturer Part Number: wm9081
• Description: Mono Dac With 2.6w Class Ab/d Speaker Driver, Dynamic Range Controller And Retune Mobile Parametric Equalizer
• Manufacturer: Wolfson Microelectronics plc

Pre-Production
POP SUPPRESSION CONTROL
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The WM9081 incorporates a number of features, including Wolfson’s SilentSwitch™ technology,
designed to suppress pops normally associated with Start-Up, Shut-Down or signal path control. To
achieve maximum benefit from these features, careful attention is required to the sequence and
timing of these controls. Note that, under the recommended usage conditions of the WM9081, these
features will be configured automatically by running the default control sequences as described in the
“Control Write Sequencer” section. In these cases, the user does not need to set these register fields
directly. Additional bias controls, also pre-programmed into Control Write Sequencer, are described
in the “Reference Voltages and Master Bias” section.
DISABLED LINE OUTPUT CONTROL
The line output is biased to VMID in normal operation. In order to avoid audible pops caused by a
disabled signal path dropping to AGND, the WM9081 can maintain LINEOUT at VMID when this
output is disabled. This is achieved by connecting a buffered VMID reference to LINEOUT. The
buffered VMID reference is enabled by setting VMID_BUF_ENA. When the line output is disabled,
the reference is connected to LINEOUT by setting LINEOUT_CLAMP. The output resistance can be
either 500Ω or 20kΩ, depending on the LINEOUT_VROI register bit.
Table 30 Disabled Line Output Control
LINE OUTPUT DISCHARGE CONTROL
The line output can be actively discharged to AGND through an internal resistor if desired. This is
desirable at start-up in order to achieve a known output stage condition prior to enabling the soft-start
VMID reference voltage. This is also desirable in shut-down to prevent the external connections from
being affected by the internal circuits. The LINEOUT pin is discharged to AGND by setting
LINEOUT_DISCH.
R4 (04h)
VMID Control
R8 (08h)
AntiPop
Control
REGISTER
ADDRESS
BIT
5
1
0
VMID_BUF_ENA
LINEOUT_VROI
LINEOUT_CLAM
P
LABEL
DEFAULT
0
0
0
Enables VMID reference for lineout
and inputs clamps
0 = Disabled
1 = Enabled
Buffered VMID to LINEOUT
Resistance. This applies when
LINEOUT_ENA = 0 and
LINEOUT_CLAMP = 1.
0 = 20k Ω from buffered VMID to
output
1 = 500 Ω from buffered VMID to
output
Clamp LINEOUT to buffered VMID.
VMID_BUF_ENA must be set. This bit
is only effective when LINEOUT_ENA
= 0. The resistance is set by
LINEOUT_VROI.
0 = Disabled
1 = Enabled (LINEOUT clamped to
VMID)
DESCRIPTION
PP, Rev 3.0, April 2009
WM9081
51