sm5841 Nippon Precision Circuits Inc, (NPC), sm5841 Datasheet - Page 11

• Manufacturer Part Number: sm5841
• Description: Audio Multi-function Digital Filter
• Manufacturer: Nippon Precision Circuits Inc, (NPC)

FUNCTIONAL DESCRIPTION
The basic arithmetic block is shown in figure 1, and
the function of each block is described in the follow-
ing sections.
8-times Oversampling (Interpolation)
The interpolation arithmetic block is comprised of 3
cascaded, 2-times FIR interpolation filters, as shown
in figure 1.
The input signal is sampled at rate fs, and then 8-
times oversampling data is output. Sampling noise in
the 0.5465fs to 7.4535fs stopband is removed by the
interpolation filter.
2nd FIR
3rd FIR
1st FIR
Figure 1. Arithmetic block diagram
2 interpolator
2 interpolator
2 interpolator
69th - order
13th - order
Attenuator
9th - order
Output
Input
4fs
fs
2fs
fs
8fs
fs
SM5841H
Digital Deemphasis (DSF1, DSF2)
The digital deemphasis filter has the same construc-
tion as analog filters. It is implemented as an IIR fil-
ter to faithfully reproduce the gain and phase
characteristics of standard analog deemphasis filters.
The filter coefficients for fs = 32.0/44.1/48.0 kHz
sampling frequency are selected by DSF1 and DSF2
when the sampling frequency is specified, as shown
in the following table.
DSF1
HIGH
HIGH
LOW
LOW
Deemphasis IIR filter
DSF2
HIGH
HIGH
LOW
LOW
fs
NIPPON PRECISION CIRCUITS—11
Deemphasis
On
On
On
Off
Sampling frequency
44.1 kHz
48.0 kHz
32.0 kHz
–