DS861PP1

33

CS5346

7.7

Channel A PGA Control - Address 08h

7.7.1

Channel A PGA Gain (Bits 5:0)

Function:

Sets the gain or attenuation for the ADC input PGA stage. The gain may be adjusted from -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 10 for ex-

ample settings.

7.8

ADC Input Control - Address 09h

7.8.1

PGA Soft Ramp or Zero Cross Enable (Bits 4:3)

Function:

Soft Ramp Enable

Soft Ramp allows level changes, both muting and attenuation, to be implemented by incrementally 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 11.

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 minimize audible artifacts. The requested level change 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 11.

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 period 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. The zero cross function is independently mon-

itored and implemented for each channel. See Table 11.

7

6

5

432

10

Reserved

Reserved

Gain5

Gain4

Gain3

Gain2

Gain1

Gain0

Gain[5:0]

Setting

101000

-12 dB

000000

0 dB

011000

+12 dB

Table 10. Example Gain and Attenuation Settings

7

6

5

432

10

Reserved

Reserved

Reserved

PGASoft

PGAZero

Sel2

Sel1

Sel0