Datasheet SSM2164 (Analog Devices) - 9
| Manufacturer | Analog Devices |
| Description | Low Cost QuadVoltage Controlled Amplifier |
| Pages / Page | 12 / 9 — SSM2164. 30k. IOUT. 500. VCA1. 560pF. 100pF. IIOUT. VCA2. IIN. Digital … |
| File Format / Size | PDF / 779 Kb |
| Document Language | English |
SSM2164. 30k. IOUT. 500. VCA1. 560pF. 100pF. IIOUT. VCA2. IIN. Digital Control of the SSM2164. OP176. VOUT. VCA3. VCA4. FROM ADDITIONAL SSM2164s
Model Line for this Datasheet
Text Version of Document
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–
