Datasheet SSM2164 (Analog Devices) - 9
| Fabricante | Analog Devices |
| Descripción | Low Cost QuadVoltage Controlled Amplifier |
| Páginas / Página | 12 / 9 — SSM2164. 30k. IOUT. 500. VCA1. 560pF. 100pF. IIOUT. VCA2. IIN. Digital … |
| Formato / tamaño de archivo | PDF / 779 Kb |
| Idioma del documento | Inglés |
SSM2164. 30k. IOUT. 500. VCA1. 560pF. 100pF. IIOUT. VCA2. IIN. Digital Control of the SSM2164. OP176. VOUT. VCA3. VCA4. FROM ADDITIONAL SSM2164s
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SSM2164
If additional SSM2164s are added, the 100 pF capacitor may
V
need to be increased to ensure stability of the output amplifier.
C 30k
Most op amps are sensitive to capacitance on their inverting
I
inputs. The capacitance forms a pole with the feedback resistor,
IOUT 500 VCA1 I
which reduces the high frequency phase margin. As more
IN 560pF
SSM2164’s are added to the mixer circuit, their output capaci-
VC 100pF
tance and the parasitic trace capacitance add, increasing the
30k
overall input capacitance. Increasing the feedback capacitor will
IIOUT
maintain the stability of the output amplifier.
500 VCA2 30k
Ω
IIN Digital Control of the SSM2164 560pF OP176 VOUT
One option for controlling the gain and attenuation of the
VC
SSM2164 is to use a voltage output digital-to-analog converter
30k
such as the DAC8426 (Figure 26), whose 0 V to +10 V output
IIOUT 500 VCA3
controls the SSM2164’s attenuation from 0 dB to –100 dB. Its
IIN 560pF
simple 8-bit parallel interface can easily be connected to a microcontroller or microprocessor in any digitally controlled
VC
system. The voltage output configuration of the DAC8426
30k
provides a low impedance drive to the SSM2164 so the attenua-
IIOUT 500 VCA4
tion can be controlled accurately. The 8-bit resolution of the
IIN 560pF
DAC and its full-scale voltage of +10 V gives an output of 3.9 mV/bit. Since the SSM2164 has a –33 mV/dB gain con-
FROM ADDITIONAL SSM2164s POWER SUPPLY FOR > 4 CHANNELS
stant, the overall control law is 0.12 dB/bit or approximately
AND BIASING CIRCUITRY
8 bits/dB. The input and output configuration for the SSM2164 is the same as for the basic VCA circuit shown
V+ GND V– MODE
earlier. The 4-to-1 mixer configuration could also be used. Figure 25. Four-Channel Mixer (4 to 1)
+15V VC V V REFOUT +10V DD IIN I 4 IOUT 18 VCA1 10V DAC8426 REFERENCE VC 2 LATCH A DAC A VOUTA I I IN IOUT 1 VCA2 LATCH B DAC B VOUTB 7 MSB VC 14 DATA BUS LSB 20 LATCH C DAC C VOUTC IIN IIOUT 19 VCA3 LATCH D DAC D VOUTD OBSOLETE 15 VC WR 16 LOGIC A1 17 CONTROL A0 IIOUT VCA4 3 5 6 IIN VSS AGND DGND POWER SUPPLY AND BIASING CIRCUITRY V+ GND V– MODE +15V –15V
Figure 26. Digital Control of VCA Gain REV. 0 –9–
If additional SSM2164s are added, the 100 pF capacitor may
V
need to be increased to ensure stability of the output amplifier.
C 30k
Most op amps are sensitive to capacitance on their inverting
I
inputs. The capacitance forms a pole with the feedback resistor,
IOUT 500 VCA1 I
which reduces the high frequency phase margin. As more
IN 560pF
SSM2164’s are added to the mixer circuit, their output capaci-
VC 100pF
tance and the parasitic trace capacitance add, increasing the
30k
overall input capacitance. Increasing the feedback capacitor will
IIOUT
maintain the stability of the output amplifier.
500 VCA2 30k
Ω
IIN Digital Control of the SSM2164 560pF OP176 VOUT
One option for controlling the gain and attenuation of the
VC
SSM2164 is to use a voltage output digital-to-analog converter
30k
such as the DAC8426 (Figure 26), whose 0 V to +10 V output
IIOUT 500 VCA3
controls the SSM2164’s attenuation from 0 dB to –100 dB. Its
IIN 560pF
simple 8-bit parallel interface can easily be connected to a microcontroller or microprocessor in any digitally controlled
VC
system. The voltage output configuration of the DAC8426
30k
provides a low impedance drive to the SSM2164 so the attenua-
IIOUT 500 VCA4
tion can be controlled accurately. The 8-bit resolution of the
IIN 560pF
DAC and its full-scale voltage of +10 V gives an output of 3.9 mV/bit. Since the SSM2164 has a –33 mV/dB gain con-
FROM ADDITIONAL SSM2164s POWER SUPPLY FOR > 4 CHANNELS
stant, the overall control law is 0.12 dB/bit or approximately
AND BIASING CIRCUITRY
8 bits/dB. The input and output configuration for the SSM2164 is the same as for the basic VCA circuit shown
V+ GND V– MODE
earlier. The 4-to-1 mixer configuration could also be used. Figure 25. Four-Channel Mixer (4 to 1)
+15V VC V V REFOUT +10V DD IIN I 4 IOUT 18 VCA1 10V DAC8426 REFERENCE VC 2 LATCH A DAC A VOUTA I I IN IOUT 1 VCA2 LATCH B DAC B VOUTB 7 MSB VC 14 DATA BUS LSB 20 LATCH C DAC C VOUTC IIN IIOUT 19 VCA3 LATCH D DAC D VOUTD OBSOLETE 15 VC WR 16 LOGIC A1 17 CONTROL A0 IIOUT VCA4 3 5 6 IIN VSS AGND DGND POWER SUPPLY AND BIASING CIRCUITRY V+ GND V– MODE +15V –15V
Figure 26. Digital Control of VCA Gain REV. 0 –9–