WM8903LGEFK/RV Wolfson Microelectronics, WM8903LGEFK/RV Datasheet - Page 68

• 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
w
A pop-suppressed start-up requires VMID to be enabled smoothly, without the step change normally
associated with the initial stage of the VMID capacitor charging. A pop-suppressed start-up also
requires the analogue bias current to be enabled throughout the signal path prior to the VMID
reference voltage being applied. The WM8903 incorporates pop-suppression circuits which address
these requirements.
The alternate current source (Start-Up Bias) is enabled by STARTUP_BIAS_ENA. The start-up bias
is selected (in place of the normal bias) by POBCTRL. It is recommended that the start-up bias is
used during start-up, before switching back to the higher quality, normal bias.
VMID_IO_ENA has the same functionality as STARTUP_BIAS_ENA. The start-up bias is enabled by
setting either of these bits.
A soft-start circuit is provided in order to control the switch-on of the VMID reference. The soft-start
control circuit is enabled by setting VMID_SOFT. Three slew rates are provided, under control of the
VMID_SOFT field. When the soft-start circuit is enabled prior to enabling VMID_RES, the reference
voltage rises smoothly, without the step change that would otherwise occur. It is recommended that
the soft-start circuit and the output signal path be enabled before VMID is enabled by VMID_RES.
A soft shut-down is provided, using the soft-start control circuit and the start-up bias current
generator. The soft shut-down of VMID is achieved by setting VMID_SOFT, STARTUP_BIAS_ENA
and POBCTRL to select the start-up bias current and soft-start circuit prior to setting VMID_RES=00.
Table 44 Soft Start Control
R4 (04h)
Bias Control
0
R5 (05h)
VMID
Control 0
REGISTER
ADDRESS
4:3
BIT
4
1
5
POBCTRL
STARTUP_BIAS_
ENA
VMID_IO_ENA
VMID_SOFT [1:0]
LABEL
DEFAULT
10
1
0
0
Selects the bias current source
0 = Normal bias
1 = Start-Up bias
Enables the Start-Up bias current
generator
0 = Disabled
1 = Enabled
Enables the Start-Up bias current
generator
0 = Disabled
1 = Enabled
(same functionality as
STARTUP_BIAS_ENA)
VMID soft start enable / slew rate
control
00 = Disabled
01 = Fast soft start
10 = Nominal soft start
11 = Slow soft start
PP, Rev 3.1, August 2009
DESCRIPTION
Pre-Production
68