wm8918 Wolfson Microelectronics plc, wm8918 Datasheet - Page 74

• Manufacturer Part Number: wm8918
• Description: Ultra Low Power Dac For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8918
POP SUPPRESSION CONTROL
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The WM8918 incorporates Wolfson’s SilentSwitch™ technology which enables pops normally
associated with Start-Up, Shutdown or signal path control to be suppressed. 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 WM8918, these features will be
configured by running the default Start-Up and Shutdown sequences as described in the “Control
Write Sequencer” section. In these cases, the user does not need to set these register fields directly.
The Pop Suppression controls relating to the Headphone / Line Output drivers are described in the
“Output Signal Path” section.
DISABLED INPUT CONTROL
The analogue inputs to the WM8918 are biased to VMID in normal operation. In order to avoid
audible pops caused by a disabled signal path dropping to AGND, the WM8918 can maintain these
connections at VMID when the relevant input stage is disabled. This is achieved by connecting a
buffered VMID reference to the input. The buffered VMID reference is enabled by setting
VMID_BUF_ENA; when the buffered VMID reference is enabled, it is connected to any unused input
pins.
Table 46 Disabled Line Input Control
R5 (05h)
VMID
Control 0
REGISTER
ADDRESS
BIT
6
0
VMID_BUF_ENA
VMID_ENA
LABEL
DEFAULT
0
0
VMID buffer to unused Inputs/Outputs
0 = Disabled
1 = Enabled
VMID Buffer Enable
0 = Disabled
1 = Enabled
PD, Rev 4.0, September 2010
DESCRIPTION
Production Data
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