WM8971L Просмотр технического описания (PDF) - Wolfson Microelectronics plc
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WM8971L Datasheet PDF : 56 Pages
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WM8971L
Advanced Information
input from charging to a high voltage which may damage the microphone on connection. R1 and R2
should be large so as not to attenuate the signal from the microphone, which can have source
impedance greater than 2kOhm. C1 together with the source impedance of the microphone and the
WM8971L input impedance forms an RF filter. C2 is a DC blocking capacitor to allow the microphone
to be biased at a different DC voltage to the MICIN signal.
MINIMISING POP NOISE AT THE ANALOGUE OUTPUTS
To minimise any pop or click noise when the system is powered up or down, the following procedures
are recommended.
POWER UP
• Switch on power supplies. By default the WM8971L is in Standby Mode, the DAC is
digitally muted and the Audio Interface, Line outputs and Headphone outputs are all OFF
(DACMU = 1 Power Management registers 1 and 2 are all zeros).
• Enable Vmid and VREF, then wait for time TBD
• Enable DACs as required
• Enable line and / or headphone output buffers as required.
• Set DACMU = 0 to soft-un-mute the audio DACs.
POWER DOWN
• Set DACMU = 1 to soft-mute the audio DACs.
• Disable all output buffers, then wait for time TBD.
• Switch off the power supplies.
POWER MANAGEMENT EXAMPLES
OPERATION MODE
POWER MANAGEMENT (1)
POWER MANAGEMENT (2)
PGAs
ADCs
DACs
Output Buffers
PGL PGR ADL ADR MBI DAL DAR LO1 RO1 LO2 RO2 MO
Stereo Headphone Playback
11000001111000
Stereo Line-in Record
11111100000000
Stereo Microphone Record
11111110000000
Mono Microphone Record
11101010000000
Stereo Line-in to Headphone Out
11000000011000
Phone Call
11100010011001
Speaker Phone Call [ROUT2INV = 1]
11100010000111
Record Phone Call [L channel = mic with 1 1 1 1 1 1 1 0 0 1 1 0 0 1
boost, R channel = RX, enable mono mix]
Table 41 Register Settings for Power Management
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AI Rev 3.0 March 2004
54
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