User Manual

DS658F4 35
CS5345
6.7 Channel A PGA Control - Address 08h
6.7.1 Channel A PGA Gain (Bits 5:0)
Function:
Sets the gain or attenuation for the ADC input PGA stage. The gain may be adjusted fro m -12 dB to
+12 dB in 0.5 dB steps. The gain bits are in two’s complement with the Gain0 bit set for a 0.5 dB step.
Register settings outside of the ±12 dB range are reserved and must not be used. See Table 11 for ex-
ample settings.
6.8 ADC Input Control - Address 09h
6.8.1 PGA Soft Ramp or Zero Cross Enable (Bits 4:3)
Function:
Soft Ramp Enable
Soft Ramp allows level changes, bo th muting and attenuation, to be implemented by increme ntally ramp-
ing, in 1/8 dB steps, from the current level to the new level at a rate of 1 dB per 8 left/right clock periods.
See Table 12.
Zero Cross Enable
Zero Cross Enable dictates that signal-level changes, either by attenuation changes or muting, will occur
on a signal zero crossing to m inimize audible artifacts. The requested level cha nge will occur after a time-
out period between 512 and 1024 sample periods (10.7 ms to 21.3 ms at 48 kHz sample rate) if the signal
does not encounter a zero crossing. The zero cross function is independently monitored and implemented
for each channel. See Table 12.
Soft Ramp and Zero Cross Enable
Soft Ramp and Zero Cross Enable dictate that signal-level changes, either by attenuation changes or mut-
ing, will occur in 1/8 dB steps and be implemented on a signal zero crossing. The 1/8 dB level change will
occur after a time-out perio d between 512 and 1024 sample periods ( 10.7 ms to 21.3 ms at 48 kHz sam-
ple rate) if the signal does not encounter a zero crossing. Th e zero cross function is independently mon-
itored and implemented for each channel. See Table 12.
76543210
Reserved Reserved Gain5 Gain4 Gain3 Gain2 Gain1 Gain0
Gain[5:0] Setting
101000 -12 dB
000000 0 dB
011000 +12 dB
Table 11. Example Gain and Attenuation Settings
76543210
Reserved Reserved Reserved PGASoft PGAZero Sel2 Sel1 Sel0