2002 Nov 22
9
NXP Semiconductors
Preliminary specification
48 kHz IEC 60958 audio DAC
UDA1352TS
8.4
Data path
The UDA1352TS data path consists of the IEC 60958
decoder, the audio feature processor, the digital
interpolator and noise shaper and the DACs.
8.4.1
IEC 60958
INPUT
The IEC 60958 decoder features an on-chip amplifier with
hysteresis, which amplifies the SPDIF input signal to
CMOS level (see Fig.4).
All 24 bits of data for left and right are extracted from the
input bitstream as well as 40 channel status bits for left and
right. These bits can be read via the L3-bus or I
2
C-bus
interface.
The UDA1352TS supports the following sample
frequencies and data bit rates:
•
f
s
= 32.0 kHz, resulting in a data rate of 2.048 Mbits/s
•
f
s
= 44.1 kHz, resulting in a data rate of 2.8224 Mbits/s
•
f
s
= 48.0 kHz, resulting in a data rate of 3.072 Mbits/s.
The UDA1352TS supports timing levels I, II and III, as
specified by the IEC 60958 standard. This means that the
accuracy of the above mentioned sampling frequencies
depends on the timing level I, II or III as mentioned in
Section 11.4.1.
8.4.2
A
UDIO
FEATURE
PROCESSOR
The audio feature processor automatically provides
de-emphasis for the IEC 60958 data stream in the static
pin control mode and default mute at start-up in the L3-bus
or I
2
C-bus mode.
When used in the L3-bus or I
2
C-bus mode, it provides the
following additional features:
•
Left and right independent volume control
•
Bass boost control
•
Treble control
•
Mode selection of the sound processing bass boost and
treble filters: flat, minimum and maximum
•
Soft mute control with raised cosine roll-off.
8.4.3
I
NTERPOLATOR
The UDA1352TS includes an on-board interpolating filter
which converts the incoming data stream from 1f
s
to 64f
s
by cascading a recursive filter and a FIR filter.
Table 2
Interpolator characteristics
8.4.4
N
OISE
SHAPER
The fifth-order noise shaper operates at 64f
s
. It shifts
in-band quantization noise to frequencies well above the
audio band. This noise shaping technique enables high
signal-to-noise ratios to be achieved. The noise shaper
output is converted to an analog signal using a filter stream
DAC.
handbook, halfpage
MGU656
13
SPDIF
75
Ω
180 pF
10 nF
UDA1352TS
Fig.4
IEC 60958 input circuit and typical
application.
PARAMETER
CONDITIONS
VALUE (dB)
Pass-band ripple
0 to 0.45f
s
±
0.03
Stop band
>0.55f
s
−
50
Dynamic range
0 to 0.45f
s
114
DC gain
−
−
5.67
