Datasheet

SSM2166
Rev. D | Page 5 of 20
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
00357-003
GND 1
G
AIN ADJUST 2
VCA
IN
3
VCA
R
4
V+14
OUTPUT13
POWER DOWN
12
ROTATION SET11
BUF OUT 5 COMP RATIO SET10
–IN 6 NOISE GATE SET9
AUDIO +IN
7
AVG CAP
8
SSM2166
TOP VIEW
(Not to Scale)
Figure 3. Pin Configuration
Table 4. Pin Function Descriptions
Pin No. Mnemonic Description
1 GND Ground.
2 GAIN ADJUST
VCA Gain Adjust Pin. A resistor from this pin to ground sets the fixed gain of the VCA. To check the setting of
this pin, make sure the compression ratio set pin (Pin 10) is grounded for no compression. The gain can be
varied from 0 dB to 20 dB. For 20 dB, leave the pin open. For 0 dB of fixed gain, a typical resistor value is
approximately 1 kΩ. For 10 dB of fixed gain, the resistor value is approximately 2 kΩ to 3 kΩ. For resistor values
<1 kΩ, the VCA can attenuate or mute (see Figure 6).
3 VCA
IN
VCA Input Pin. A typical connection is a 10 μF capacitor from the buffer output pin (Pin 5) to this pin.
4 VCA
R
Inverting Input to the VCA. This input can be used as a nonground reference for the audio input signal (see the
Applications Information section).
5 BUF OUT Input Buffer Amplifier Output Pin. This pin must not be loaded by capacitance to ground.
6 −IN
Inverting Input to the Buffer. A 10 kΩ feedback resistor, R1, from the buffer output (Pin 5) to this input pin and
a resistor, R2, from this pin through a 1 μF capacitor to ground give gains of 6 dB to 20 dB for R2 = 10 kΩ to 1.1 kΩ.
7 AUDIO +IN Input Audio Signal. The input signal should be ac-coupled (0.1 μF typical) into this pin.
8 AVG CAP
Detector Averaging Capacitor. A capacitor, 1 μF to 22 μF, to ground from this pin is the averaging capacitor
for the detector circuit.
9 NOISE GATE SET
Noise Gate Threshold Set Point. A resistor to V+ sets the level below which input signals are downward
expanded. For a 0.7 mV threshold, the resistor value is approximately 380 kΩ. Increasing the resistor value
reduces the threshold (see Figure 5).
10 COMP RATIO SET
Compression Ratio Set Pin. A resistor to ground from this pin sets the compression ratio, as shown in Figure 2.
Figure 19 gives resistor values for various rotation points.
11 ROTATION SET
Rotation Point Set Pin. This pin is set by adding a resistor to the positive supply. This resistor together with
the gain adjust pin determines the onset of limiting. A typical value for this resistor is 17 kΩ for a 100 mV
rotation point. Increasing the resistor value reduces the level at which limiting occurs (see Figure 9).
12 POWER DOWN
Power-Down Pin. Connect this pin to ground for normal operation. Connect this pin to the positive supply
for power-down mode.
13 OUTPUT Output Signal.
14 V+ Positive Supply, 5 V Nominal.