SM5841H Datasheet, PDF (12/20 Pages) Nippon Precision Circuits Inc – Audio Multi-function Digital Filter

SM5841H
System Clock (CKI, CKO, CKSL)
Two system clock frequencies, 384fs and 256fs, can
be used. The clock is input on CKI. The CKI input
inverter has a feedback resistor to allow AC-coupled
input clocks. The system clock is also buffered and
then output on CKO. The system clock frequency
selection and the internal clock frequency are shown
in the following table.
Parameter
CKI input system clock frequency (f_SYS)
CKO clock frequency
Internal clock frequency
Serial output clock frequency
CKSL
HIGH LOW
384fs 256fs
384fs 256fs
128fs 128fs
192fs 256fs
CKSL
CKI
CKO
CKSL = H
1/3
1/2
CKSL = L
to timing controller
Internal system clock
(128fs)
to timing controller
Figure 2. Clock generator circuit
Noise Shaper and I/O Data Length (WSL1, WSL2)
The SM5841H has functions that can be used to sup-
press the level of requantization noise due to the
inherent arithmetic rounding-off that occurs in digi-
tal signal processing.
s 16/18-bit input
The input interface accepts 16 and 18-bit input
source data. That means that if 16-bit source data
is digitally processed, for example in a sound field
control or other DSP, the output can be input to the
SM5841H without the same need for rounding-
off, thereby avoiding the requantization noise that
would otherwise occur.
s 16/18/20-bit output
The output interface can support 18 and 20-bit
output data, making connection to 18 or 20-bit
D/A converters possible. As a result, the requanti-
zation noise generated after digital processing can
be greatly reduced.
s Noise shaper function
The 1st-order noise shaper processing occurs on
the digital filter output. It reduces the requantiza-
tion noise for 16 and 18-bit input signals to levels
inherent in 18 and 20-bit output modes, respec-
tively. The noise shaper does no processing on 20-
bit output data.
There are 4 input data and output data length combi-
nations possible, selected by the state of WSL1 and
WSL2 as shown in the following table.
WSL1 WSL2
HIGH HIGH
HIGH LOW
LOW HIGH
LOW LOW
Noise
shaper
Off
On
On
On
Input bit
length
18 bits
18 bits
16 bits
16 bits
Output bit
length
20 bits
18 bits
18 bits
16 bits
NIPPON PRECISION CIRCUITS—12