WM8903LGEFK/RV Wolfson Microelectronics, WM8903LGEFK/RV Datasheet - Page 74

• 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

WM8903
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If periodic updates to the DC offset correction is required, then DCS_MODE should be modified.
Setting this field to 11b selects START_UPDATE servo mode, which causes the DC offset to be
measured and corrected on a periodic basis. The default time between updates is approximately 10
minutes. Scheduling periodic updates enables the WM8903 to compensate for any change in DC
offsets which might have occurred due to power supply drift or other factors. To modify this within the
Start-Up sequence, the data in WSEQ Address 22 should be updated (see “Control Write
Sequencer”) before running the sequence.
Table 49 DC Servo Control
To reduce power consumption when unused audio outputs are disabled, the DC Servo correction
should also be disabled. The WM8903 provides the capability to quickly resume the necessary DC
Servo correction when the outputs are re-enabled, without the time delay associated with the
START_STOP mode of DC Servo operation.
If the DC Servo correction is disabled using the DCS_ENA bits, but the DCS_MASTER_ENA bit is
maintained at 1, then the DC Servo will retain the latest correction values in its memory. These
values will be re-applied when the DC Servo is later enabled via the DCS_ENA bits.
An alternative method to apply known correction settings is to read the correction values from the
WM8903 register map and to store these for later use. After DC offset correction has been
performed, the applicable correction values can be read from the fields in the Servo Readback
registers R81 to R84 described in Table 50.
Setting DCS_MODE to 00b or 01b selects WRITE_STOP mode and WRITE_UPDATE mode
respectively. WRITE_STOP mode is similar to START_STOP mode, except that the DC Servo
correction factors are read from internal registers, instead of being calculated from the measured
output conditions. In the same way, WRITE_UPDATE mode is similar to START_UPDATE mode.
When the DC Servo is commanded to one of these modes, the initial DC offset correction values are
read from the _WRITE_VAL field in registers R71 to R74 described in Table 50.
Selecting WRITE_STOP or WRITE_UPDATE mode applies initial settings which should be written to
registers R71 to R74 before the DC Servo is enabled. In WRITE_STOP mode, no further DC
correction is applied. In WRITE_UPDATE mode, the DC Servo will periodically measure and adjust
the DC offset correction. Similar to START_UPDATE mode, the default time between updates is
approximately 10 minutes.
R67 (43h)
DC Servo 0
R69 (45h)
DC Servo 2
REGISTER
ADDRESS
BIT
3:0
1:0
4
DCS_MASTER_EN
A
DCS_ENA[3:0]
DCS_MODE [1:0]
LABEL
DEFAULT
0000
00
1
DC Servo Master Control
0 = DC Servo Reset
1 = DC Servo Enabled
DC Servo Enable
[3] - HPOUTL enable
[2] - HPOUTR enable
[1] - LOUTL enable
[0] - LOUTR enable
DC Servo Mode
00 = WRITE_STOP
01 = WRITE_UPDATE
10 = START_STOP
11 = START_UPDATE
PP, Rev 3.1, August 2009
DESCRIPTION
Pre-Production
74