SSM2120 Datasheet, PDF (11/12 Pages) Analog Devices – Dynamic Range Processors/Dual VCA

SSM2120/SSM2122
FADER AUTOMATION
The SSM2120 can be used in fader automation systems to serve
two channels. The inverting control port is connected through
an attenuator to the VCA control voltage source. The noninverting
control port is connected to a control circuit (such as Figure 6)
which senses the input signal level to the VCA. Above the
threshold voltage, which can be set quite low (for example
–60 dBV), the VCA operates at its programmed gain. Below
this threshold the VCA will downward expand at a rate deter-
mined by the +V_C control port attenuator. By keeping the release
time constant in the 10 ms to 25 ms range, the modulation of
the VCA standing noise floor (–80 dB at unity-gain), can be
kept inaudibly low.
The SSM2300 8-channel multiplexed sample-and-hold IC
makes an excellent controller for VCAs in automation systems.
Figure 16 shows the basic connection for the SSM2122 operating
as a unity-gain VCA with its noninverting control ports grounded
and access to the inverting control ports. This is typical for fader
automation applications. Since this device is a pinout option of
the SSM2120, the VCAs will behave exactly as described
earlier in the VCA section.
The SSM2122 can also be used with two or more op amps to
implement complex voltage-controlled filter functions. Biquad
and state-variable two-pole filters offering low pass, bandpass
and high pass outputs can be realized. Higher order filters can
also be formed by connecting two or more such stages in series.
10pF
+15V
0.1µF
36kΩ
1
16
10pF
2
15
SIG_{OUT 1}
1/2
TL082
200Ω
V+
3
14
50kΩ*
–V_C1
SIG_{IN 1}
V–
36kΩ
220kΩ
200Ω
4
13
SSM2122
5
12
6
11
2000pF
150kΩ
47Ω ^V+
7
10
0.1µF
8
9
200Ω
220kΩ
200Ω
36kΩ
1/2
TL082
V+
SIG_{OUT 2}
50kΩ*
V–
36kΩ
2000pF
47Ω
–V_C2
SIG_{IN 2}
–15V
*OPTIONAL CONTROL FEEDTHROUGH TRIM
Figure 16. SSM2122 Basic Connection (Control Ports at 0 V)
REV. C
–11–