wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 131

• Manufacturer Part Number: wm8400
• Description: Wolfson Audioplustm Hi-fi Audio Codec And Power Management Unit For Mobile Multimedia
• Manufacturer: Wolfson Microelectronics plc

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Pre-Production
AUDIO CODEC POWER MANAGEMENT
LOOPBACK
Setting the LOOPBACK register bit enables digital loopback. When this bit is set the output data from
the ADC audio interface is fed directly into the DAC data input.
Table 76 Loopback Control
Note:
The WM8400 has three control registers that allow users to select which CODEC functions are
active. For minimum power consumption, unused functions should be disabled. To avoid any pop or
click noise, it is important to enable or disable functions in the correct order.
VMID_MODE is the enable for the Vmid reference, which defaults to disabled and can be enabled as
a 2x50kΩ potential divider or, for low power maintenance of Vref when all other blocks are disabled,
as a 2x300kΩ potential divider.
1.
2.
3.
REGISTER
ADDRESS
R6 (06h)
R2 (02h)
REGISTER
ADDRESS
Master Mode: ADC and DAC left/right clocks must be set to the same pin when using
LOOPBACK function (ALRCGPIO1=1)
Slave Mode: It is recommended to set ALRCGPIO1=1 as well, otherwise ADCLRC and
DACLRC must be running at the same BCLK rate and in phase.
When the digital sidetone is enabled, ADC data will continue to be added to DAC data when
LOOPBACK is enabled
13
12
11
10
9
8
4
BIT
0
BIT
SPK_MIX_ENA
(rw)
SPK_ENA
(rw)
OUT3_ENA
(rw)
OUT4_ENA
(rw)
LOUT_ENA
(rw)
ROUT_ENA
(rw)
MIC1BIAS_ENA
(rw)
LOOPBACK
LABEL
LABEL
0b
0b
0b
0b
0b
0b
0b
DEFAULT
0b
DEFAULT
Speaker Mixer Enable
0 = disabled
1 = enabled
Speaker Output Enable
0 = disabled
1 = enabled
OUT3 and OUT3MIX Enable
0 = disabled
1 = enabled
OUT4 and OUT4MIX Enable
0 = disabled
1 = enabled
LOUT (Left Headphone Output) Enable
0 = disabled
1 = enabled
ROUT (Right Headphone Output) Enable
0 = disabled
1 = enabled
MICBIAS Enable
0 = OFF (high impedance output)
1 = ON
Digital Loopback Function
0 = No loopback
1 = Loopback enabled (ADC data output
is directly input to DAC data input).
DESCRIPTION
DESCRIPTION
PP, April 2009, Rev 3.0
WM8400
131