SM5865AM Просмотр технического описания (PDF) - Nippon Precision Circuits
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SM5865AM Datasheet PDF : 17 Pages
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SM5865AM
FUNCTIONAL DESCRIPTION
Quantization Noise Reduction
The SM5865AM employs a 3rd-order 23-level quantizer noise shaper to effectively reduce quantization noise
in the audio band. The quantization noise component at 16fs to 96fs operation is shown in figure 1.
0
10
0 dB sine wave equivalent white noise level
20
30
40
16-bit, fs quantization noise level
50
60
70
80
Quantization noise
(dB)
90
100
110
120
130
20-bit, fs quantization noise level
140
150
160
24-bit, fs quantization noise level
170
180
0
0.5
1
1.5
2
2.5
3
Frequency (fs)
Figure 1. Quantization noise level
16fs
24fs
32fs
48fs
64fs
96fs
3.5
4
Internal Oversampling Operation
The SM5865AM accepts data output from an 8-times or 4-times oversampling digital filter, and oversampled
internally again up to the noise shaper operating rate. The internal oversampling factor is determined automati-
cally from the system clock input frequency and the input sampling frequency. This internal oversampling fac-
tor (n) must be an integer satisfying the conditions shown in table 1.
Table 1. Operating conditions
Parameter
CKDVN = HIGH
CKDVN = LOW
fWCKI and fCKI compulsory conditions1
fCKI = fWCKI × 8 × n
where n = 1, 2, 3, ...
fCKI = fWCKI × 16 × n
where n = 1, 2, 3, ...
Noise shaper operating frequency
fns
=
fWCKI × n=
f---C---K----I
8
fns
=
fWCKI × n=
f---C---K----I
16
1. fWCKI = word clock frequency, fCKI = input system clock frequency, n = internal oversampling factor
NIPPON PRECISION CIRCUITS—9
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