Production Data
WM9715L
UNUSED ANALOGUE INPUTS AND OUTPUTS
When analogue inputs or outputs are disabled, they remain internally connected to VREF (AVDD/2)
through a large resistor. This maintains the potential at that node and helps to eliminate pops when
the pins are re-enabled.
There are several exceptions to this. Firstly, when VREF itself is disabled (PR3 = 1 in register 26h),
unused analogue pins are not held at AVDD/2. Additionally:
•
The MIC1 input is disconnected from VREF if all of the following register settings are
applied:
PD0 = 1 in register 24h
AND PR0 = 1 in register 26h
AND MS = 00 in register 0Eh
AND (RECSL = 000 or RECSR = 000 in register 1Ah)
•
The MIC2 input is disconnected from VREF if all of the following register settings are
applied:
PD0 = 1 in register 24h
AND PR0 = 1 in register 26h
AND MS = 10 in register 0Eh
AND (RECSL = 000 or RECSR = 000 in register 1Ah)
•
•
The PCBEEP input is disconnected from VREF if PR2 = 1 in register 26h
The PCBEEP input is also disconnected from VREF if the exact following register
settings are applied:
PD9 = 1 in register 24h or B2H = 1 in register 0Ah
AND (PD8 = 1 in register 24h or B2H = 1 in register 0Ah)
AND (PD7 = 1 in register 24h or B2S = 1 in register 0Ah)
AND (PD6 = 1 in register 24h or B2P = 1 in register 0Ah)
For MIC1 and MIC2, pop issues can be circumvented by disconnecting the microphone inputs from
the record selector (RECSL = RECSR = 001 in register 1Ah) in sleep or standby modes.
However, should it be necessary to maintain the VREF potential at MIC1, MIC2 or PCBEEP, this can
be achieved by choosing any suitable register settings that are not identical to those shown above.
PD Rev 4.0 December 2007
57
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
