Datasheet

STA309A Registers
Doc ID 13855 Rev 4 23/67
Interpolation ratio select
The STA309A has variable interpolation (oversampling) settings such that internal
processing and DDX output rates remain consistent. The first processing block interpolates
by either 4 times, 2 times, or 1 time (pass-through).
The oversampling ratio of this interpolation is determined by the IR bits.
I
Setting the DSPB bit bypasses the biquad function of the Omega DDX core.
Table 11. Interpolation ratio bits
Bit RW RST Name Description
3RW0IR0
Interpolation ratio select: selects internal interpolation
ratio based on input I
2
S sample frequency
4RW0IR1
Table 12. IR sample rates
IR[1,0]
Input sample rate
fs (kHz)
1
st
stage interpolation ratio
00 32 4-times oversampling
00 44.1 4-times oversampling
00 48 4-times oversampling
01 88.2 2-times oversampling
01 96 2-times oversampling
10 176.4 Pass-through
10 192 Pass-through
11 DSD DSD to 176.4 kHz conversion
Table 13. DSPB bit
Bit RW RST Name Description
0 RW 0 DSPB
DSP bypass bit:
0: normal operation
1: bypass of biquad and bass/treble functions
Table 14. COS bits
COS[1,0] CKOUT frequency
00 PLL output
01 PLL output / 4
10 PLL output / 8
11 PLL output / 16