ADG GENERAL DESCRIPTIONThe ADG is a low voltage CMOS device containing two independently selectable single-pole, double-throw (SPDT). Model Temperature Range Package Description Package Option Branding SSMRMZ-REEL .. Ω CMOS, Dual MUX/SPDT Audio Switch ADG Devices Inc. BOARD EVAL FOR AD, 8, 1. $ Buy · EVAL- ADGEBZ · Analog Devices Inc. BOARD EVAL FOR ADG, 6, 1. $ . Buy.

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It is also excellent for improving vocal clarity in communications and public address systems. A low noise voltage controlled amplifier VCA provides a gain that is dynamically adjusted by a control loop to maintain a set compression characteristic.

برنامه‌نویسان، سیستم‌های توسعه‌یافته بوردها و کیت‌های ارزیابی و مقدماتی

The compression ratio is set by a single resistor and can be varied from: Signals above the rotation point are limited to prevent overload and to eliminate popping. A downward expander noise gate prevents amplification of background noise or hum. This results in optimized signal levels prior to digitization, thereby eliminating the need for additional gain or attenuation in the digital domain.

The flexibility of setting the compression ratio and the time constant of the level detector, coupled with two values of rotation point, make the SSM easy to integrate in a wide adg8844 of microphone conditioning applications. G Information furnished by Analog Devices is believed to be accurate and reliable.

However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P. BoxNorwood, MAU. This page is dynamically generated by Analog Devices, Inc. A dynamic change to the content on this page will not trigger a change to either the revision number or the content of the product data sheet. This dynamic page may be frequently modified.

G Changes to Ordering Guide E Change to Signal Path Section Changes to Ordering Guide Universal Changes to Ordering Guide A Edits to Specifications This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied.

Exposure to absolute maximum rating conditions for extended periods may affect device reliability. VCA Gain Figure 8.

Low Voltage Microphone Preamplifier with Variable Compression and Noise Gating SSM2167

Small Signal Transient Response Figure. Large Signal Transient Response Figure 2. Large Signal Transient Response Rev. Designed primarily for voice-band applications, this integrated circuit provides amplification, limiting, variable compression, and noise gate.

User adjustable compression ratio, noise gate threshold, and two different fixed gains optimize circuit operation for a variety of applications. The SSM also features a low power shutdown mode for battery-powered applications. The dotted line indicates the transfer characteristic for a unity-gain amplifier.


For input signals in the range of VDE downward expansion to VRP rotation pointan r db change in the input level causes a db change in the output level. Here, r is defined as the compression ratio. The compression ratio may be varied from: Input signals above VRP are compressed with a fixed compression ratio of approximately This region of operation is the limiting region. Varying the compression ratio has no effect on the limiting region.

G Page 8 rnz 2 The ad8g84 between the compression region and the limiting region is axg884 to as the limiting threshold or the rotation point. The gain of the system with an input signal level of VRP is the fixed gain, 8 dbv for the SSM, regardless of the compression ratio.

Input signals below VDE are downward expanded; that is, a db change in the input signal level causes approximately a 3 db change in the output level. As a result, the gain of the system is small for very small input signal levels, even though it may be quite large for small input signals above VDE.

The audio input signal is processed by the input buffer and then by the VCA. The input buffer is a unity-gain stable amplifier that can drive the low impedance input of the VCA and an internal rms detector. The VCA is a low distortion, variable gain amplifier whose gain is set by the side-chain control circuitry. An external blocking capacitor C2 must be used between the buffer output and the VCA input. An aluminum electrolytic capacitor is an economical choice.

The net gain from input to output can be as high as 40 db, asg884 on the gain set by the control circuitry. The nominal output dc voltage of the device is approximately.

The bandwidth of the SSM is quite wide at all gain settings. The upper 3 db point is over MHz at gains as high as 30 db. The GBW plots are shown in Figure 5. Whereas the noise of the input buffer is fixed, the input-referred noise of the VCA is a function of gain.

The VCA input noise is designed to be at a minimum when the gain is at a maximum, thereby maximizing the usable dynamic range of the part.

Low Voltage Microphone Preamplifier with Variable Compression and Noise Gating SSM PDF

For optimal low frequency operation of the level detector down to 0 Hz, the value of the capacitor should be 2. Some experimentation with larger values for CAVG may be necessary to reduce the effects of excessive low frequency ambient background noise.

The value of the averaging capacitor affects sound quality: This time constant controls both the steady state averaging in the rms detector as well as the release time for compression, that is, the time it takes for the system gain to increase due to a decrease in input signal. The attack time, the time it takes for the gain to be reduced because of a sudden increase in input level, is controlled mainly by internal circuitry that speeds up the attack for large level changes.

In most cases, this limits overload time to less than 35 ms. In Figure 3 and Figure 4, the input signal to the SSM not shown is a series of tone bursts in six successive 0 db steps.


The tone bursts range from 66 dbv 0. As illustrated in these figures, the attack time of the rms level detector is dependent only on CAVG, but the release times are linear ramps whose decay times are dependent on both CAVG and the input signal step size. The control circuitry subtracts a dc voltage from this signal, scales it, and sends the result to the VCA to control the gain. The gain control of the VCA is logarithmic a linear change in control signal causes a db change in gain.

This effect is shown in Figure 7. AGC performance is achieved with compression ratios between 2: The downward expansion threshold may be set between 40 dbv and 55 dbv, as shown in Table 5.

The downward expansion threshold is inversely proportional to the value of this resistance: This relationship is illustrated in Figure 8. This feature allows the SSM to limit the maximum output, preventing clipping of the following stage, such as a codec or ADC. The rotation point for the SSM is set internally to 24 dbv 63 mv rms.

In this state, the input and output circuitry of the SSM assumes a high impedance state; as such, the potentials at the input pin and the output pin are determined by the external circuitry connected to the SSM The SSM takes approximately ms to settle from a shutdown to power-on command.

For power-on to shutdown, the SSM requires more time, typically less than sec. Cycling the power supply to the SSM can result in quicker settling times: The SSM shutdown current is related to both temperature and voltage.

The following applications hints should be considered for the PCB. The layout should minimize possible capacitive feedback from the output of the SSM back to its input.

Do not run input and output traces adjacent to each other. A single-point star ground implementation is recommended in addition to maintaining short lead lengths and PCB runs. In applications where an analog ground and a digital ground are available, the SSM and its surrounding circuitry should be connected to the analog ground of the system. As a result of these recommendations, wire-wrap board connections and grounding implementations are to be explicitly avoided.

G Page of 2. MHz No phase reversal Low input currents:. High Accuracy, Ultralow IQ. Low Voltage, MHz Quad 2: MHz to 8 GHz High accuracy: Ultraprecision, 36 V, 2. At power-up, this device autocalibrates its input offset voltage.

V to 8 V Excellent Load Drive.

The bias supply drives. Designed for use in portable consumer, medical, and. In addition, MOS inputs. V to 8 V Excellent Load. The regulator delivers up to 1A from. Filterless, High Efficiency, Mono 2. It provides up to mA. At power-up, this device.

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