WM8903LGEFK/RV Wolfson Microelectronics, WM8903LGEFK/RV Datasheet - Page 79

• Manufacturer Part Number: WM8903LGEFK/RV
• Description: Audio CODECs ULTRA LOW PWR HI FI CODEC
• Manufacturer: Wolfson Microelectronics

Specifications of WM8903LGEFK/RV

• Audio Codec Type: Stereo Codec
• No. Of Adcs: 2
• No. Of Dacs: 2
• No. Of Input Channels: 6
• No. Of Output Channels: 8
• Adc / Dac Resolution: 24bit
• Sampling Rate: 96kHz
• Operating Temperature Range: -40°C To +85°C
• Rohs Compliant: Yes
• Adcs / Dacs Signal To Noise Ratio: 96dB
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Production Data
POP SUPPRESSION CONTROL
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The WM8903 incorporates Wolfson’s SilentSwitch™ technology which enables pops normally
associated with Start-Up, Shut-Down 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 WM8903, these features will be
configured by running the default Start-Up and Shut-Down 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 / OUTPUT CONTROL
The analogue inputs to the WM8903 and the Differential Line (Speaker) outputs are biased to VMID
in normal operation. In order to avoid audible pops caused by a disabled signal path dropping to
AGND, the WM8903 can maintain these connections at VMID when the relevant input or output
stage is disabled. This is achieved by connecting a buffered VMID reference to the input or output.
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 by setting the
BUFIO_ENA register bit. When buffered VMID is enabled, it is connected to any disabled Differential
Line outputs (speaker driver outputs) by setting VMID_TIE_ENA. The resistance associated with
VMID_TIE_ENA can be either 500Ω or 20kΩ, depending on the VROI register bit.
Table 51 Disabled Input / Output Control
DIFFERENTIAL LINE OUTPUT DISCHARGE CONTROL
The differential line output paths can be actively discharged to AGND through internal resistors 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 Differential Line outputs
(speaker driver outputs) can be discharged to AGND by setting SPK_DISCHARGE.
Table 52 Differential Line Output Discharge Control
R5 (05h)
VMID
Control 0
R65 (41h)
R65 (41h)
REGISTER
REGISTER
ADDRESS
ADDRESS
BIT
BIT
7
6
0
0
1
VMID_TIE_ENA
BUFIO_ENA
VMID_BUF_ENA
VROI
SPK_DISCHARG
E
LABEL
LABEL
DEFAULT
DEFAULT
0
0
0
0
0
VMID buffer to Differential Lineouts
0 = Disabled
1 = Enabled
(only applies when relevant outputs
are disabled, ie. SPLK=0 or SPKR=0.
Resistance is controlled by VROI.)
VMID buffer to unused Inputs/Outputs
0 = Disabled
1 = Enabled
VMID Buffer Enable
0 = Disabled
1 = Enabled
Select VMID_TIE_ENA resistance for
disabled Differential Lineouts
0 = 20k ohm
1 = 500 ohm
Speaker Discharge Enable
0 = Disabled
1 = Enable
PD, Rev 4.0, September 2010
DESCRIPTION
DESCRIPTION
WM8903
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