AK4555 Datasheet, PDF (10/17 Pages) Asahi Kasei Microsystems – Low Power & Small Package 20bit ΔΣ CODEC

ASAHI KASEI
[AK4555]
„ Audio Serial Interface Format
Data is shifted in/out the SDTI/SDTO pins using SCLK and LRCK inputs. The data is MSB first, 2’s compliment. The
following formats are also valid when SCLK is 64fs: 16-bit data followed by four zeros and 18-bit data followed by two
zeros.
LRCK
0 1 2 3 16 17 18 19 20 21 30 31 0 1 2 3 16 17 18 19 20 21 30 31 0 1
SCLK(64fs
SDTO(o)
19 18
4 3210
19 18
4 3 21 0
SDTI(i)
16bit
SDTI(i)
18bit
SDTI(i)
20bit
15 14
17 16
19 18
0
Don’t Care 15 14
210
Don’t Care 17 16
4 3 2 1 0 Don’t Care 19 18
0
Don’t Care
210
Don’t Care
4 3 2 1 0 Don’t Care
0 1 2 3 8 9 10 11 12 13 14 15 0 1 2 3 8 9 10 11 12 13 14 15 0 1
SCLK(32fs)
SDTO(o)
0 15 14
8 7 6 5 4 3 2 1 0 15 14
8 7654 321 0
SDTI(i)
0 15 14
8 7 6 5 4 3 2 1 0 15 14
8 7654 321 0
Lch Data
Figure 4. Audio Interface Timing
Rch Data
„ De-emphasis filter
The DAC of AK4555 includes the digital de-emphasis filter (tc=50/15µs) by IIR filter. This filter corresponds to three
frequencies (32kHz, 44.1kHz and 48kHz). The de-emphasis filter selected by DEM0 and DEM1 pins is enabled for input
audio data. The de-emphasis is also disabled at DEM1 pin = “L” and DEM0 pin = “H”.
DEM1 pin DEM0 pin
Mode
L
L
44.1kHz
L
H
OFF
H
L
48kHz
H
H
32kHz
Table 3. De-emphasis filter control
„ Digital High Pass Filter
The AK4555 has a Digital High Pass Filter (HPF) for DC-offset cancel. The cut-off frequency of the HPF is 3.4Hz at
fs=44.1kHz and the frequency response at 20Hz is −0.12dB. It also scales with the sampling frequency (fs).
MS0363-E-01
- 10 -
2005/08