SA2159 SILAN | Alldatasheet
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HANGZHOU SILAN MICROELECTRONICS CO.,LTD Rev: 1.0 2005.04.22 Http: www.silan.com.cn Page 1 of 11 VOLTAGE CONTROLLED AMPLIFIER FOR ELECTRONIC VOLUME CONTROL SIP8
DESCRIPTION
The SA2159 is a voltagecontrolled amplifier (VCA) circuit. The chip is a highperformance current– in/currentout devices including two opposing polarity, voltagesensitive control ports. Due to super low noise application, the circuit adopts high hFE. Complementary NPN/PNP pairs configuration. It requires little external support circuitry and selects a spaceefficient plastic 8pin single– in– line (SIP) package. The SA2159 VCA combinesa number of advantages such as low noise, low distortion, low offset and high gainbandwidth to offer discrete performance at IC prices.
FEATURES
- Wide dynamic range:>115dB * Wide gain range:>130dB * Logarithmic gain control * Low distortion:(0.008%@0dB gain, 0.035%@15dB gain) * Wide gainbandwidth: 6MHz * Single in– line package * Dual gaincontrol ports(pos/neg) ORDERING INFORMATIONS Device Package SA2159 SIP8
APPLICATIONS
- Faders * Expanders * Compressors * Equalizers * Oscillators * Filters * Automation syste ms BLOCK DIAGRAM
HANGZHOU SILAN MICROELECTRONICS CO.,LTD Rev: 1.0 2005.04.22 Http: www.silan.com.cn Page 2 of 11 ABSOLUTE MAXIMUM RATINGS (Ta mb=25°C) Characteristic Symbol Ratings Unit Positive Supply Voltage VCC +15 V Negative Supply Voltage VEE 15 V Supply Current ICC 30 mA Power Dissipation PD 330 mW Operating Temperature Range TOP 20~+75 °C Storage Temperature Range TST 40~+125 °C RECOMMENDED OPERATING CONDITIONS Characteristics Symbol Test conditions Min Typ Max Unit Supply Voltage VCC +4 +12 +15 V Supply Voltage VEE 4 12 15 V Bias Current ISET VCC VEE=24V 2 2.4 mA Signal Current IIN+IOUT ISET=2.4mA 125 550 µ A ELECTRICAL CHARACTERISTICS (Unless otherwise specified, VCC+=+15V, VCC=15V, Ta mb =25°C) Characteristics Symbol Test conditions Min Typ Max Unit Supply Current ICC No signal 2 3 mA Equiv. Input Bias Current IB No signal 5 20 nA Input Offset Voltage VOFF(IN) No signal +10 mV Output Offset Voltage VOFF(OUT) ROUT=20KΩ 0 dB gain THD adj for min 1 mV Gain Cell Idling Current IIDLE 20 µ A GainControl Constant EC+ EC Ta mb=20°C 60dB<gain<+40 dB Pins 2&4(fig.13) Pin 3 5.8 5.8 5.9 5.9 6.1 6.1 mV/dB mV/dB GainControl Temp Co Δ EC/Δ Ta mb Ta mb~27°C 0.33 %/°C GainControl Linearity 60~40dB gain 0.5 2 % Offset Isolation(Fig.14) EC+=360mV, EC=+360mV 110 115 dB Output Noise en(OUT) 20Hz20kHz ROUT=20KΩ 0dBain +15dBain 97 88 89 82 dBV dBV Symme try Control Voltage VSYM AV=0dB, THD<0.07% 4 0 +4 mV Total Harmonic Distortion THD IOUT=30µ A,1KHz 0dB gain +20dB gain 20dB gain 0.007 0.02 0.02 0.07 0.10 0.15
1 IN Signal input
2 EC+ Positive exponential control
3 EC Negative exponential control
4 EC+(SYM) Symmetry control
5 V Negative power
6 GND Ground
7 V+ Positive power
8 OUT Output
the summed voltage back to a current through a bipolar antilog circuit. input pin 1, which is maintained at a virtual ground potential by the internal op amp. Figure 1. Simplified internal circuit diagram
simultaneously turns Q3 and D3 on. Thus, the input signal current is forced to flow through Q3 and D3. collector of Q3, and IS is the reversesaturation current of Q3. Gain = 20 log Av = EC / 0.0059, where the unit of Gain is dB. Figure 2. Gain versus control voltage at 25°C
dB) of the gain is the same . “ thumps” if gain commands changes very large and fast. gives rise to even order distortion production. Figure 3. Typical THD versus symmetry voltage distortion in the output waveform. shown in Figure 4.) Either pin 3, or pins 2 and 4, or both ports together may be used for gain control. Mathematically:Av = 10 EC / 0.118, or Gain = 20 log Av = EC / 0.0059, where the unit of Gain is dB.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD Rev: 1.0 2005.04.22 Http: www.silan.com.cn Page 8 of 11 As mentioned above, because input and output signals are currents, not voltages, the current input/output mode provides great flexibility in application. Internal negative feedback loop provides a virtual ground to the input pin 1 (See Figure 1). Within the linear range of the device, the input resistor (shown as 20kΩ in typical application circuit) should be scaled to convert the available ac input voltage to a current. In order to obtain best distortion performance, peak input currents should be kept under 1 mA. The input impedances must be less than 30kΩ to assure the circuit stability. The feedback impedances around the internal op amp (essentially Q1/D1 and Q3/D3) are fixed. Low values for the input resistor will require more closedloop gain from the op amp. Since the openloop gain naturally falls off at high frequencies, this resistor should be kept to 10kΩ or above in order to prevent high frequency distortion when the gain is too much. Distortion vs. frequency for a 1V signal at 0dB gain with a 20 kΩ input resistor is shown in Figure 9. As mentioned above, any dc input currents will cause dc signals in the output. The dc signals will be modulated by gain command, in turn causing audible thump. Therefore, in order to control quality audio applications, capacitive coupling must be adopted in actual application, which can give acceptable low frequency performance. Figure 9. Typical THD Vs. frequency, 0dB gain converted to a voltage. Choose the external op amp can improve audio performance. VCA, so that most op amps can operate steadily. The capacitance at pin 8 is typically 30 pf. currents may help accommodate low supply voltages.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD Rev: 1.0 2005.04.22 Http: www.silan.com.cn Page 9 of 11 The process characteristics and internal power consumption determine the highest supply voltage. +15V is the nominal limit. A resistive current source determining the current available for the core is connected to the negative supply terminal. As mentioned before, this source must supply 200µ A current over the sum of the required signal currents including input signal current, output signal current and the bias to run the rest of the IC. 2.4mA is recommended for most pro audio applications where +15V supplies are common and headroom is important. Bypassing at pin 5 is not necessary because pin 5 is a current supply, not a voltage supply. Pin 6 is used as a ground reference for the VCA which connect the noninverting input of the internal op amp, as a portion of the internal bias network. It m ay not be used as an additional input pin. Voltage control Pin 3 is the primary voltage control pin. This point controls gain is inversely proportional to applied voltage: positive voltage causes loss, negative voltage causes gain. The current gain of the VCA is unity when pin 3 is at 0V and varies with voltage at approximately 5.9m/dB, at room temperature. As implied by the equation for Av at the foot of page 3, the gain is sensitive to temperature. The constant of proportionality is 0.33% of the decibel gain commanded, per degree Celsius, referenced to 27°C (300K). The formula is: Where Δ T is the difference between the actual te mperature and room te mperature (27°C) For most audio applications, this change with temperature is of little consequence. However, if necessary, it may be compensated by a resistor which varies its value by 0.33%/°C. When pin 3 is used for voltage control, Pin 2 is connected to ground and pin 4 is used to apply a small symmetry voltage (~±4 mV) to correct for VBE mismatches within the VCA IC. Therefore, in order to obtain optimum performance, pin 4 connects with an external impedance of approximately 50Ω . A trim pot is used to adjust the voltage between pin 4 and pin 2 as shown in typical application circuit. Voltage adjustment range is ±4 mV. Pin 2 and pin4 can be used together as an opposite sense voltage control port (See Figure 4). Pin 3 may be grounded and pin 2 driven against the symmetryadjustment voltage. The change of voltage at pin 4 does have a small effect on the symmetry voltage, but this is of little practical consequence in most applications. The chip can combine all control ports together with differential drive (See Figure 10). While the driving circuitry is more complex, this configuration offers better performance at high attenuation levels (<90dB) where the single control port circuits begin to saturate Q1 (for EC drive) or Q3 (for EC+ drive). When either of these transistors saturates, the internal op amp will accommodate the change in current demand by responding with a small change in its input offset voltage. This leads to an accumulation of charge on the input capacitor, which in turn can cause thump when the high attenuation is suddenly removed(e.g., when a muted channel is opened). Differential control drive avoids the large dc levels otherwise required to command high attenuation (+600mV or 100dB gain at pin 3 alone, vs. ±300mV when using both pin 3 and pins 2 and 4). Control port drive impedance In order to reduce distortion, it is necessary to use low source impedance at the control port. Thus, this often suggests an op amp is used to drive the control port directly (see below under noise considerations). However, due to falling loop gain at high frequencies, the closedloop output impedance of an op amp typically rises. The output impedance is therefore inductive at high frequencies. Excessive inductance can cause the VCA to
HANGZHOU SILAN MICROELECTRONICS CO.,LTD Rev: 1.0 2005.04.22 Http: www.silan.com.cn Page 11 of 11 TYPICAL APPLICATION CIRCUIT PACKAGE OUTLINE SIP8 Unit: mm