SM5879AV
Attenuation
The SM5879AV loads the attenuation factor with
serial data by means of the microcontroller interface,
thus enabling attenuation operation.
MLEN
MCK
MDT
A0
(LSB)
D0
A1
A3
A4
A5
A6
0
A2
(MSB)
D1
D2 D3 D4
D5 D6
D7
Figure 7. Method of setting the attenuation factor
The attenuation computation is performed by multi-
plying the output of the internal 7-bit UP/DOWN
counter output data by the signal data. When the con-
tents of the counter are DATT, gain can be expressed
by the following equations.
L channel
DATT
127
---------------
=
×
Gain 20 log
[dB]
[dB]
R channel
DATT
127
---------------
=
×
Gain 20 log
When DATT = 0, this becomes -∞.
When the attenuation factor is changed, it is
smoothly changed from the previous setting until it
reaches the value of the new setting as expressed by
the above equations. The time required to change
gain is approximately 1024 fs ≈ 23.2 msec when the
time required to change one step of the attenuation
factor is approximately 8 / fs ≈ 181.4 µsec over the
range 0 dB to -∞.
Setting1
Setting5
Setting3
(Gain)
Setting2
Setting4
Time
Figure 8. Example of attenuation gain
NIPPON PRECISION CIRCUITS—17
NPC [ NIPPON PRECISION CIRCUITS INC ]
