SM5846AP_06 Datasheet, PDF (21/36 Pages) Nippon Precision Circuits Inc – Multi-function Digital Filter

SM5846AP
Output data round-off
Output data round-off processing is required because
the internal data length of the digital filter is different
from the output data length (internal data processing
width > output data width).
The SM5846AP can select either normal round-off
or dither round-off on the output data. Round-off
processing can be selected either by input pin or con-
trol flag settings.
MDS
HIGH
LOW
DITH
pin
HIGH
LOW
×
DITH
flag
×
HIGH
LOW
Output
data
round-off
Notes
Dither
round-off
Normal
round-off
Normal
round-off
The DITH flag is set
HIGH (default) after a
system reset.
Dither
round-off
Normal round-off
Normal round-off is carried out by adding 1/2 LSB
to the filter output data to form 20/24-bit output data,
depending on the selected output data length.
Dither round-off
Dither round-off is carried out by adding a pseudo-
random number between 0 and 1 LSB, derived from
a rectangular distribution, to the filter output data to
form 20/24-bit output data, depending on the
selected output data length. The random number
rectangular distribution is shown below (average =
1/2 LSB).
Probavility
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
0 1/2 1 (LSB)
Overflow limiter
If an overflow or underflow condition occurs after
round-off or filter arithmetic processing, the output
data will be fixed at positive or negative maximum
value.
SEIKO NPC CORPORATION —21