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SM5852CS

NIPPON PRECISION CIRCUITS—15

FUNCTIONAL DESCRIPTION

Dynamic Range Compression

Dynamic range compression varies the effective

ampliﬁcation of the input as a function of the input

signal level. The mode control block selects one of 6

dynamic

range

compression

characteristics

according the states of DB/DS, MOD1 and MOD2.

Also, dynamic range compression can be turned

OFF, bypassing all processing.

Attack Time Selection

The input interface block incorporates a peak hold

circuit to determine the input level. The peak hold

circuit has a time constant of

τ = 250 ms, and the

peak hold output is attenuated and then compared

with the next input level. Therefore, the dynamic

range

compression

recovery

time

constant

effectively

τ = 250 ms.

The attack time coefﬁcient of the input signal, to

pass through the selected attack time LPF, is

determined by the input level.

Two attack time low-pass ﬁlter characteristics are

available, selected by the state of OPT.

OPT = HIGH, Attack-1 characteristics, fC = 350

Hz, 2nd-order LPF (Q = 0.5)

OPT = LOW, Attack-2 characteristics, fC = 150

Hz, 2nd-order LPF (Q = 0.5)

The attack time is the time required by the circuit to

return to the set value after a sudden increase in the

input. The recovery time is the time required by the

circuit to return to the set value after a sudden

decrease in the input.

Soft Muting

Soft muting is active when MUTEN is LOW. When

MUTEN is LOW, the attenuation changes smoothly

from 0 to

−∞ dB in 1024/fs, or approximately 23.2

ms.

When MUTEN goes HIGH, soft muting is released

and the attenuation changes smoothly from

−∞ to 0

dB, again taking approximately 23.2 ms.

Also, if a MUTEN transition occurs while the

attenuation is changing, the attenuation then changes

smoothly in the direction speciﬁed by the new level

of MUTEN.

DB/DS, OPT Switching Shock Noise

The soft muting function is also activated to

eliminate switching shock noise when DB/DS or

OPT change state. When DB/DS or OPT change

state, the attenuation changes to

−∞ dB, the internal

circuit settings are activated and then soft muting is

released.

Therefore,

maximum

time

approximately 46.4 ms is required to change the

compression mode. Of course, if the attenuation is

already

−∞ dB after soft muting using MUTEN, then

no time is required to change compression mode.

Reset Initialization

RSTN should be set LOW at power-ON and after

reacquiring synchronization. Note that if RSTN is

LOW for longer than 1 µs, a through-current ﬂows in

the LSI’s internal dynamic circuits because the

internal clock is stopped. The through-current has no

rated value, so the reset pulse should be kept as short

as possible at all times other than at power-ON.

When RSTN goes from LOW to HIGH, initialization

hold is released and the initialization routine ﬁrst

resets the internal data over an interval of 4fs. During

the initialization routine, the output data is forcibly

muted so that there is no output signal.

DB/DS

MOD2

MOD1

Compression mode

LOW

HIGH

LOW

HIGH

LOW

HIGH

Off

HIGH

LOW

HIGH

LOW

HIGH

LOW

HIGH

Off

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