wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 61

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

WM8400
Pre-Production
INPUT PGA VOLUME CONTROL
Each of the four Input PGAs has an independently controlled gain range of -16.5dB to +30dB in
1.5dB steps. The gains on the inverting and non-inverting inputs to the PGAs are always equal. Each
Input PGA can be independently muted using the PGA Mute bits described in Table 23. Maximum
mute attenuation is achieved by simultaneously disconnecting the corresponding inputs, as
described in Table 22.
To prevent "zipper noise", a zero-cross function is provided, so that when enabled, volume updates
will not take place until a zero-crossing is detected. In the event of a long period without zero-
crossings, a timeout function is available. When this function is enabled (using the TOCLK_ENA
register bit), the volume will update after the timeout period if no earlier zero-cross has occurred. The
timeout period is set by TOCLK_RATE. See “Clocking and Sample Rates” for more information on
these fields.
The IPVU bit controls the loading of the input PGA volume data. When IPVU is set to 0, the PGA
volume data will be loaded into the respective control register, but will not actually change the gain
setting. The LIN12, RIN12, LIN34, RIN34 volume settings are all updated when a 1 is written to
IPVU. This makes it possible to update the gain of all input paths simultaneously.
The Input PGA Volume Control register fields are described in Table 23 and Table 24.
PP, April 2009, Rev 3.0
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