Precision Monolithics Inc. DYNAMIC RANGE PROCESSOR/DUAL FEAT
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SSM-2120/SSM-2122
Precision Monolithics Inc.
DYNAMIC RANGE PROCESSOR/DUAL
FEATURES
GENERAL DESCRIPTION
SSM-2120 monolithic integrated circuit designed purpose processing dynamic signals various analog systems including audio. This "dynamic range processor" consists VCAs level detectors (the SSM-2122 consists VCAs only). These circuit blocks allow user logarithmically control gain attenuation signals presented level detectors depending their magnitudes. This allows compression, expansion limiting signals, some primary applications SSM-2120.
0.01% +10dBV In/Out 100dB Dynamic Range Control Feedthrough 100dB Level Detection Range Log/Antilog Control Paths External Component Count
APPLICATIONS
Compressors Expanders Limiters Circuits Voltage-Controlled Filters Noise Reduction Systems Stereo Noise Gates
CONNECTIONS
ORDERING INFORMATION
PACKAGE PLASTIC 16-PIN SSM2122P PLASTIC 22-PIN SSM2120P
OPERATING TEMPERATURE RANGE -10°C +50°C
THRESH CONOUT SIGOUT +VC1 -VC1 SIGIN RECIN IREF
SIGOUT SIGOUT -VC2
+VC2
SIGIN
RECIN
CONOUT
THRESH
SIMPLIFIED SCHEMATIC (VCA Section Only)
SSM-2120 22-PIN PLASTIC (P-Suffix)
+VC1 -VC1 IREF SIGIN
SIGOUT +VC2 -VC2
SIGIN
SSM-2122 16-PIN PLASTIC (P-Suffix)
SIGNAL INPUT
Protected under U.S. Patents #4,471,320 #4,560,947. Other Patent Pending. SSM-2120/SSM-2122 mask work protected under Semiconductor Chip Protection 1983.
IREF
CURRENT MIRRORS
SIGNAL
5/90, Rev.
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
Supply Voltage ±18V Operating Temperature Range -10° +55°C Junction Temperature +150°C Storage Temperature -65° +150°C Maximum Current into 10mA Lead Temperature Range (Soldering, sec) 300°C
ABSOLUTE MAXIMUM RATINGS
PACKAGE TYPE 16-Pin Plastic 22-Pin Plastic
(Note
UNITS °C/W °C/W
NOTE: specified worst case mounting conditions, i.e., specified device socket P-DIP.
ELECTRICAL CHARACTERISTICS ±15V, +25°C, IREF 200µA, unless otherwise noted.
SSM-2120/SSM-2122
PARAMETER POWER SUPPLY CONDITIONS UNITS
Supply Voltage Range Positive Supply Current Negative Supply Current VCAs ISIGNAL (In/Out) Output Offset Control Feedthrough (Trimmed) Gain Control Range Control Sensitivity Gain Scale Factor Drift Frequency Response Isolation Current Gain (Unity-Gain) Noise (20kHz Bandwidth) LEVEL DETECTORS (SSM-2120 ONLY) Dynamic Range Input Current Range Rectifier Input Bias Current Output Sensitivity Pin) Output Offset Voltage Frequency Response 1mAp-p 10µAp-p 1µAp-p CONTROL AMPLIFIERS (SSM-2120 ONLY) Input Bias Current Output Drive (Max Sink Current) Input Offset Voltage
ROUT 36k, -30dB
Unity-Gain
Unity-Gain Less 1kHz
±387 -100 -0.25 0.03
±400
±413
+10dBV IN/OUT 0dBV
mV/dB -3300 ppm/°C +0.25 0.005 0.02 ±0.5 3000 µAp-p mV/dB 1000 ±0.5
NOTE: Specifications subject change; consult latest data sheet.
5/90, Rev.
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
VOLTAGE-CONTROLLED AMPLIFIERS
voltage-controlled amplifiers full Class current current devices with complementary dB/V gain control ports. control sensitivities +6mV/dB -6mV/dB. resistor divider (attenuator) used adapt sensitivity external control voltage range control port. best less attenuator resistor ground. INPUTS signal inputs behave virtual grounds. input current compliance range determined current into reference current pin.
current consumption VCAs will directly proportional IREF which nominally 200µA. device will operate lower current levels which will reduce effective dynamic range VCAs. With 200µA reference current, input output clip points will ±400µA. general: ICLIP ±2IREF OUTPUTS outputs designed interface directly with virtual ground inputs external operational amplifiers configured current-to-voltage converters. outputs must operate virtual ground because output stage's finite output impedance. power supplies selected compliance range determines values input output resistors needed. example, with ±15V supplies ±400µA maximum input output current, choose ROUT output compliance range ±14.4 Note that signal path through including output current-to-voltage converter noninverting.
IREF
REFERENCE reference current determines input output current compliance range VCAs. current into reference connecting resistor voltage reference about volts above current will
RREF
BLOCK DIAGRAM (SSM-2120)
SSM-2122
+VC1
INPUT
OUTPUT
RECIN
THRESH
-VC1
FULL WAVE RECTIFIER
|IIN|
CONOUT
+VC2 THRESH RECIN INPUT OUTPUT
CONOUT
FULL WAVE RECTIFIER
|IIN|
-VC2
5/90, Rev.
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
PERFORMANCE GAIN (+10dBV IN/OUT 1kHz)
PERFORMANCE Figures show typical noise performance VCAs over ±20dB gain/attenuation. Full Class operation provides very THD. TRIMMING VCAs control feedthrough (CFT) pins optional control feedthrough null points. nulling usually required applications such noise gating downward expansion. trimming used, leave pins open. Trim Procedure Apply 100Hz sine wave control point attenuator. signal peaks should correspond control voltages which induce VCAs maximum intended gain least 30dB attenuation. Adjust potentiometer minimum feedthrough. (Trimmed control feedthrough typically well under when maximum gain unity using input output resistors.) Applications such compressor/limiters typically require control feedthrough trimming because operates unitygain unless signal large enough initiate gain reduction. this case signal masks control feedthrough. This trim ineffective voltage-controlled filter applications. LEVEL DETECTION CIRCUITS SSM-2120 contains independent level detection circuits. Each circuit contains wide dynamic range full-wave rectifier, logging circuit unipolar drive amplifier. These circuits will accurately detect input signal level over 100dB range from 30nA peak-to-peak. LEVEL DETECTOR THEORY OPERATION Referring level detector block diagram Figure RECIN input virtual ground. next block implements full-wave rectification input current. This current then into logging transistor (Q1) whose pair transistor (Q2) fixed collector current IREF. output then:
.003
GAIN (dB)
NOISE GAIN (20kHz BANDWIDTH)
THRESH CONOUT IREF FULL WAVE RECTIFIER |IIN|
NOISE (dBV)
GAIN (dB)
FIGURE Typical Noise Performance
RCON
INPUT
RECIN
RREF
FIGURE Level Detector
5/90, Rev.
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
VLOG
With capacitor output then average absolute value IIN. (The unfiltered output broad flat plateaus with sharp negative spikes zero crossing. This reduces "work" that averaging capacitor must particularly frequencies.) Note: natural assume that with addition averaging capacitor, output would become average absolute value IIN. However, since capacitor forces ground emitter output transistor, capacitor charging currents proportional antilog voltage base output transistor. Since base voltage output transistor absolute value IIN, antilog terms cancel, capacitor becomes linear integrator with charging current directly proportional absolute value input current. This effectively inverts order averaging logging functions. signal output therefore average absolute value IIN.
FIGURE Detector Output
USING DETECTOR PINS RECIN, LOGAV, THRESH CONOUT
When applying signals RECIN (rectifier input) input series resistor should followed leakage blocking capacitor since RECIN voltage approximately 2.1V above ground. Choose ±1.5mA peak signal. ±15V operation this corresponds value 10k.
10dB Step 20dB Step 30dB Step 40dB Step 50dB Step 60dB Step 11.28ms 16.65 18.15 18.61
FIGURE Overlayed Detector Output
1.5M value RREF from average -15V will establish 10µA reference current logging transistor (Q1). This will bias transistor middle detector's dynamic current range optimize dynamic range accuracy. outputs buffered amplified unipolar drive amps. 39k, resistor network THRESH provides gain attenuator from CONOUT (control output) appropriate control port establishes control sensitivity. attenuator resistor ground choose RCON desired sensitivity. Care should taken minimize capacitive loads control outputs CONOUT. long lines capacitive loads present, best connect series resistor RCON closely CONOUT possible. DYNAMIC LEVEL DETECTOR CHARACTERISTICS Figures show dynamic performance level detector change signal level. input detector (not shown) series 500ms tone bursts 1kHz successive 10dBV steps. tone bursts start level -60dBV (with =10k) return -60dBV after each successive 10dB step. Tone bursts range from -60dBV +10dBV. Figure shows logarithmic level detector output. output detector 3mV/dB amplifier gain which yields 120mV/dB. Thus, output CONOUT seen increase 1.2V each 10dBV increase input level. DYNAMIC ATTACK DECAY RATES Figure shows output levels overlayed using storage scope. attack rate determined step size value
CAV. attack time final value function step size increase. chart Figure shows values total settling times within final value with 10µF. When step sizes exceed 40dB, increase settling time larger steps negligible. calculate attack time final value value CAV, simply multiply value chart 10µF. decay rates linear ramps that dependent current (set RREF) value CAV. integration decay time circuit derived from formula:
21.46 26.83 28.33 27.79
Decrementation Rate dB/s)
30.19 35.56 37.06 37.52 (+144µs) (+46µs)
46.09 51.46 52.96 53.42
FIGURE Settling Time (tS) 10µF, (CAV 10µF)
5/90, Rev.
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
CONTROL CIRCUIT
TYPICAL DOWNWARD EXPANDER CONTROL CURVE
THRESHOLD
MONO RECIN
THRESHOLD CONTROL
CONOUT RCON
|IIN|
VCON
MONO STEREO
1.5M
VIN(dB)
*LOWER LIMIT FIXED CONNECTING
RESISTOR FROM RECIN GROUND
FIGURE Noise Gate/Downward Expander Control Circuit Typical Response.
CONTROL CIRCUIT
MONO
THRESHOLD CONTROL RCON
TYPICAL COMPRESSOR/LIMITER CONTROL CURVE
THRESHOLD
|IIN|
VCON
MONO STEREO
VIN(dB)
THRESH
1.5M
*UPPER LIMIT FIXED VALUE PULL
RESISTOR (RPV) CONNECTED POSITIVE SUPPLY
FIGURE Compressor/Limiter Control Circuit Typical Response.
APPLICATIONS
following applications SSM-2120 both VCAs level detectors conjunction assimilate variety functions. first section describes arrangement threshold control each control circuit configuration. These control circuits form foundation applications follow which include downward expander, compressor/limiter compandor. THRESHOLD CONTROL Figure shows control circuit typical downward expander while Figure shows typical control curve. Here, threshold potentiometer adjusts provide negative unipo-
control output. This typically used noise gate, downward expander, dynamic filter applications. This potentiometer used applications control signal level versus control voltage characteristics. noise gate, downward expander compressor/limiter applications, this potentiometer will establish onset control action. sensitivity control action depends value positive unipolar control output diodes shown Figure This useful compressor/limiter applications. Figure shows typical response. Bipolar control outputs realized adding resistor from output This useful compandor circuits
5/90, Rev.
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
CONTROL CIRCUIT
GAIN MONO RECIN |IIN|
TYPICAL COMPANDOR CONTROL CURVES
CONOUT THRESH
VCON
MONO STEREO
1.5M
CONTROL CIRCUIT
THRESHOLD EXP. FIGURE MONO THRESHOLD COM. FIGURE
VIN(dB)
*UPPER LOWER LIMITS ESTABLISHED
VALUES RLL, RESPECTIVELY
FIGURE Compandor Control Circuit Typical Curves.
VOUT(dB)
INPUT/OUTPUT CURVE
EXPANSION THRESHOLD
COMPRESSION THRESHOLD VIN(dB)
FIGURE Control Circuit Stereo Compressor/Limiter with Noise Gating Input/Output Curve shown Figure with response Figure value resistor will determine maximum output from control amplifier. STEREO COMPRESSOR/LIMITER control circuits Figures used conjunction produce composite control voltages. Figures show this type circuit transfer function stereo compressor/limiter which also acts downward expander noise gating. output noise absence signal will dependent noise current-to-voltage converter amplifier expansion ratio high enough. discussed Threshold Control section, control circuit Figure including diodes, yields positive unipolar control outputs.
5/90, Rev.
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
10pF 10pF
SIGNAL INPUT
2200pF
TRANSMISSION STORAGE MEDIUM
2200pF SIGNAL OUTPUT
RECIN |IIN|
|IIN|
4.7M
RECIN
4.7M
FIGURE Companding Noise Reduction System
OUTPUT SIGNAL LEVEL (dB)
COMPANDING NOISE REDUCTION SYSTEM complete companding noise reduction system shown Figure Normally, obtain overall gain unity, value equal values RC/E will determine compression/expansion ratio. Table shows compression/expansion ratios ranging from 1.5:1 full limiting with corresponding values RC/E.
IREF
RREF 4.7M
OVERALL RESPONSE
EXPANSION
25dB COMPRESSION
example compression/expansion ratio plotted Figure Note that signal compression increases gain level signals reduces gain high levels while expansion does reverse. result system same original input signal except that been compressed before being sent given medium expanded after recovery. compression/expansion ratio needed depends medium being used. extreme example, household tape player would require higher compression/expansion ratio than professional stereo system.
INPUT SIGNAL LEVEL (dB)
FIGURE Companding Noise Reduction with Compression/Expansion Ratio
TABLE
INPUT SIGNAL INCREASE (dB) *AGC Compression Only GAIN (REDUCTION INCREASE) (dB) 6.67 10.00 13.33 15.00 16.00 17.33 18.00 20.00 COMPRESSOR ONLY OUTPUT SIGNAL INCREASE (dB) 13.33 10.00 6.67 5.00 4.00 2.67 2.00 EXPANDER ONLY OUTPUT SIGNAL INCREASE (dB) 22.67 30.00 33.33 35.00 36.00 37.33 38.00 40.00 COMPRESSION/ EXPANSION RATIO 1.5:1 7.5:1 10:1 AGC*/Limiter
RC/E 11,800 7,800 5,800 5,133 4,800 4,415 4,244 3,800
VCONTROL-
(mV/dB)
5/90, Rev.
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
2.2µF 20Hz (WIDEBAND)
THRESHOLD CONTROL
AUDIO INPUT
|IIN| 160k THRESH CONOUT
3.3µF 1.5M 160k
3300pF RECIN 5kHz (HIGH FREQUENCY)
THRESH |IIN| CONOUT 5.6k
SIGIN
3.3µF
1.5M
100pF
SIGOUT
2200pF
AUDIO OUTPUT
FIGURE Dynamic Noise Filter Circuit DYNAMIC FILTER Figure shows control circuit dynamic filter capable single ended (non-encode/decode) noise reduction. Such circuits usually suffer from loss high-frequency content signal levels because their control circuits detect absolute amount highs present signal. This circuit, however, measures wideband level well high-frequency band level produce composite control signal combined ratio respectively. upper detector senses wideband signals with cutoff 20Hz while lower detector 5kHz cutoff sense only highfrequency band signals. This approach allows very good noise masking with minimum loss "highs" when signal level goes below threshold.
5/90, Rev.
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
VTHRESH
50.6 50.6 50.6 50.6 50.6 50.6 17.8 2.75
HIGH-FREQUENCY SIGNAL LEVEL (dB)
Figures 13a-c show filter's frequency response with threshold potentiometer centered, Data taken applying 300Hz signal wideband detector 20kHz signal high-frequency band detector simultaneously. These figures correspond filter characteristics 50dB, 70dB 90dB dynamic range program source material, respectively. system could thus treat signals from anything ranging from 1/4" magnetic tape high-performance compact disc players. Note that Figure control circuit designed that minimum cutoff frequency about 1kHz. This occurs control circuit detects noise floor source material. Dynamic filtering limits signal bandwidth less than 1kHz unless enough highs detected signal cover noise floor mid- high-frequency range. this case filter opens pass more audio band more highs detected. filter's bandwidth extend 50kHz with nominal signal level input. other signal levels with varying high-frequency content, filter will close required bandwidth. Here, noise outside band removed while perceived noise masked other signals within band. Even this system, however, certain amount mid- high-frequency components will lost, especially during transients very signal levels. This circuit does address frequency noise such "hum" "rumble."
11.7 11.7 11.7
HIGH-FREQUENCY SIGNAL LEVEL (dB)
WIDEBAND SIGNAL LEVEL (dB)
VTHRESH Centered
50.6
15.1
50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 49.2 49.2 49.2 49.2
WIDEBAND SIGNAL LEVEL (dB)
VTHRESH
50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6 50.6
HIGH-FREQUENCY SIGNAL LEVEL (dB)
12.3 17.3 17.8 17.8 17.8 17.8 17.8 17.8
WIDEBAND SIGNAL LEVEL (dB)
FIGURE Filter Response
5/90, Rev.
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
THRESHOLD 160k SIGNAL INPUT RIN1 20Hz CONOUT
SIGNAL OUTPUT
RECIN |IIN|
CAV1 1.5M
2200pF
DOWNWARD EXPANDER
160k 5kHz RIN2
CONOUT 5.6k 100pF
RECIN
|IIN|
CAV2
1.5M
FIGURE Dynamic Filter with Downward Expander
2200pF
DYNAMIC FILTER WITH DOWNWARD EXPANDER composite single-ended noise reduction system realized combination dynamic filtering downward expander. shown Figure output from wideband detector also connected control port second which connected series with sliding filter. This will downward expander with threshold that tracks that filter. Although both these techniques used noise reduction, each alone will pass appreciable amounts noise under some conditions. When used together, both contribute distinct advantages while compensating each other's deficiencies. Downward expansion uses controlled level detector. This section maintains dynamic range integrity levels above user adjustable threshold level. input level decreases below threshold, gain reduction occurs increasing rate (see Figure 15). This technique reduces audible noise fade outs level signal passages keeping standing noise floor well below program material. This technique itself less effective signals with predominantly frequency content such bass solo where wideband frequency noise would heard full level. Also, since level detector time constant signal averaging, percussive material modulate noise floor causing "pumping" "breathing" effect.
dynamic filter downward expander techniques used together employed more subtly achieve given level noise reduction than would required used individually. 30dB noise reduction realized while preserving crisp highs with minimum transient side effects.
NOISE FILTER
FIGURE Typical Downward Expander Characteristics -30dB Threshold Level (1:1.5 Ratio)
5/90, Rev.
OUTPUT (dB)
INPUT (dB)
SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL
+15V 0.1µF 10pF 220k 50k* -VC1 SININ 2000pF 150k SSM-2122 0.1µF 220k 50k* 2000pF -VC2 SIGIN 10pF
SIGOUT
TL082
TL082
SIGOUT
FIGURE SSM-2122 Basic Connection (Control Ports FADER AUTOMATION SSM-2120 used fader automation systems serve channels. inverting control port connected through attenuator control voltage source. noninverting control port connected control circuit (such Figure which senses input signal level VCA. Above threshold voltage, which quite (for example -60dBV), operates programmed gain. Below this threshold will downward expand rate determined control port attenuator. keeping release time constant 25ms range, modulation standing noise floor (-80dB unity-gain), kept inaudibly low. SSM-2300 8-channel multiplexed sample-and-hold makes excellent controller VCAs automation systems. Figure shows basic connection SSM-2122 operat-
-15V OPTIONAL CONTROL FEEDTHROUGH TRIM
unity-gain with noninverting control ports grounded access inverting control ports. This typical fader automation applications. Since this device pinout option SSM-2120, VCAs will behave exactly described earlier section. SSM-2122 also used with more amps implement complex voltage-controlled filter functions. Biquad state-variable two-pole filters offering lowpass, bandpass highpass outputs realized. Higher order filters also formed connecting more such stages series.
5/90, Rev.
0590 0299G7M PRINTED Precision Monolithics Inc. reserves right make changes leading improved performance, reliability manufacturability. Although every effort made ensure accuracy information contained this data sheet, assumes responsibility circuitry unless entirely contained within product. premium performance this product achieved through advanced processing technology. products guaranteed meet exceed published specifications. 1990
Precision Monolithics Inc. Bourns Company 1500 Space Park P.O. 58020 Santa Clara, 95052-8020 310-371-9541 727-1550 843-1515
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