SSM2166

Rev. D | Page 5 of 20

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

V+

14

OUTPUT

13

POWER DOWN

12

ROTATION SET

11

COMP RATIO SET

10

NOISE GATE SET

9

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 Input Pin. A typical connection is a 10 μF capacitor from the buffer output pin (Pin 5) to this pin.

4

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.