SM5843AS1 datasheet(14/24 Pages) NPC

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SM5843A

×1

NIPPON PRECISION CIRCUITS—14

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 for the sharp roll-

off (response 1) characteristic, 0.745fs to 7.255fs for

the slow roll-off (response 2) characteristic, is

removed by the interpolation ﬁlter.

Digital Deemphasis

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 three sets of ﬁlter coefﬁcients for the three fs =

32.0/44.1/48.0

kHz

sampling

frequencies

are

selected by FSEL1 and FSEL2 when the sampling

frequency is speciﬁed, as shown in the following

table. Deemphasis is ON when DEMP is HIGH, and

OFF when DEMP is LOW.

Note that test mode is not available for operation.

Figure 1. Arithmetic block diagram

Input

2 - times oversampling

153 - tap (response 1 )or

25 - tap (response 2 )

FIR

2fs

2 - times oversampling

29 - tap FIR

4fs

Deemphasis IIR

filter

Deemphasis ON

4fs

Mute function

4fs

8fs

Output

Deemphasis OFF

2 - times oversampling

17 - tap FIR

FSEL1

FSEL2

Sampling frequency (fs)

LOW

44.1 kHz

LOW

HIGH

48 kHz

HIGH

LOW

Test mode

HIGH

32 kHz

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