WM8903LGEFK/RV Wolfson Microelectronics, WM8903LGEFK/RV Datasheet - Page 69

• 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

Pre-Production
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 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.
The 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. The ground-referenced Headphone outputs and
Line outputs are shorted to AGND by default; the short circuit is removed on each of these paths by
setting the applicable fields HPL_RMV_SHORT, HPR_RMV_SHORT, LINEOUTL_RMV_SHORT or
LINEOUTR_RMV_SHORT.
The ground-referenced Headphone output and Line output drivers are designed to suppress pops
and clicks when enabled or disabled. However, it is necessary to control the drivers in accordance
with a defined sequence in start-up and shut-down to achieve the pop suppression. It is also
necessary to schedule the DC Servo offset correction at the appropriate point in the sequence (see
“DC Servo”). Table 45 and Table 46 describe the recommended sequences for enabling and
disabling these output drivers.
Step 1
Step 2
Step 3
Step 4
Step 5
Table 45 Headphone / Line Output Enable Sequence
Step 1
Step 2
Table 46 Headphone / Line Output Disable Sequence
SEQUENCE
SEQUENCE
HPL_ENA = 1
HPR_ENA = 1
HPL_ENA_DLY = 1
HPR_ENA_DLY = 1
DC offset correction
HPL_ENA_OUTP = 1
HPR_ENA_OUTP = 1
HPL_RMV_SHORT = 1
HPR_RMV_SHORT = 1
HPL_RMV_SHORT = 0
HPR_RMV_SHORT = 0
HPL_ENA = 0
HPL_ENA_DLY = 0
HPL_ENA_OUTP = 0
HPR_ENA = 0
HPR_ENA_DLY = 0
HPR_ENA_OUTP = 0
HEADPHONE DISABLE
HEADPHONE ENABLE
LINEOUTL_ENA = 1
LINEOUTR_ENA = 1
LINEOUTL_ENA_DLY = 1
LINEOUTR_ENA_DLY = 1
DC offset correction
LINEOUTL_ENA_OUTP = 1
LINEOUTR_ENA_OUTP = 1
LINEOUTL_RMV_SHORT = 1
LINEOUTR_RMV_SHORT = 1
LINEOUTL_RMV_SHORT
LINEOUTR_RMV_SHORT
LINEOUTL_ENA
LINEOUTL_ENA_DLY
LINEOUTL_ENA_OUTP
LINEOUTR_ENA
LINEOUTR_ENA_DLY
LINEOUTR_ENA_OUTP
LINEOUT DISABLE
LINEOUT ENABLE
PP, Rev 3.1, August 2009
WM8903
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