AVAGO AMMP-6650 Dc â 30 ghz variable attenuator Datasheet

­AMMP-6650
DC – 30 GHz Variable Attenuator
Data Sheet
Description
Features
The AMMP-6650 is a voltage controlled variable attenuator in a surface mount package, designed to operate from
DC to 30 GHz. It is fabricated using Avago Technologies
enhancement mode pHEMT MMIC process and requires
only positive voltage control. The distributed topology
of the AMMP-6650 facilitates broadband operation by
absorbing parasitic effects of its series and shunt FETs.
An on-chip DC reference circuit may be used to maintain
optimum VSWR for any attenuation setting or to provide
more linear attenuation versus voltage response.
• 5 x 5 mm Surface Mount Package
Package Diagram
• Wide Frequency Range DC - 30 GHz
• Attenuation Range 20dB
• Single Positive Bias Supply
• Unconditionally Stable
Applications
• Microwave Radio Systems
• Satellite VSAT, DBS Up / Down Link
• LMDS & Pt – Pt mmW Long Haul
DCin
NC
DCout
1
2
3
• Broadband Wireless Access (including 802.16 and 802.20
WiMax)
• WLL and MMDS loops
Functional Block Diagram
RFin
8
4
7
6
5
V1
NC
V2
RFout
DCin
NC
DCout
1
2
3
DC
reference circuit
RFin
8
4
variable
attenuator
7
V1
6
5
NC
V2
RFout
Pin
1
2
3
4
5
6
7
8
Function
DC in
NC
DC out
RF out
V2
NC
V1
RF in
Top View
Note : Package base : GND
Attention: Observe precautions for
handling electrostatic sensitive devices.
ESD Machine Model = 80 V
ESD Human Body Model = 400 V
Refer to Avago Application Note A004R:
Electrostatic Discharge, Damage and Control.
Note: MSL Rating = Level 2A
Electrical Specifications
1. Small/Large -signal data measured in a fully de-embedded test fixture form TA = 25°C.
2. Data obtained from on-wafer measurement
3. This final package part performance is verified by a functional test correlated to actual performance at one or more
frequencies.
4. Specifications are derived from measurements in a 50 Ω test environment. Aspects of the amplifier performance may
be improved over a more narrow bandwidth by application of additional conjugate, linearity, or low noise (Гopt)
matching.
Table 1. RF Electrical Characteristics [1,2]
Symbol
Parameters and Test Conditions
Units
Freq. [GHz]
Minimum Attenuation
(Reference State)
|S21|
V1 = 1.5 V
V2 = 0.0 V
dB
Maximum Attenuation
dB
|S21|
V1 = 0.0 V
V2 = 1.25 V
Minimum
Typical
Maximum
2
0.9
1.5
10
2.0
2.5
20
0.9
2.5
30
2.1
3.0
2
23
26.6
10
23
28.0
20
23
30.0
30
23
35.6
Return Loss (In/Out)
at Reference State
V1=1.5 V, V2=0.0 V
dB
<30
10
Return Loss (In/Out)
at Max. Attenuation
V1=0.0 V, V2=1.25 V
dB
<30
10
Table 2. Recommended Operating Range
1. Ambient operational temperature TA = 25°C unless otherwise noted.
2. Data obtained from on-wafer measurement
Parameter
Min.
Typical
Max.
Unit
Test Condition
V1 Control Current (Min Attenuation), Ic_V1_ref
1.93
2.0
mA
Vse=1.2V, Vsh=0
V2 Control Current (Min Attenuation), Ic_V2_ref
0.8
2.5
uA
Vse=0V, Vsh=1.2V
V1 Control Current (Max Attenuation), Ic_V1_max
1.1
2.5
uA
Vse=0V, Vsh=1.2V
V2 Control Current (Max Attenuation), Ic_V2_max
1.41
1.5
mA
Vse=1.2V, Vsh=0
Table 3. Absolute Minimum and Maximum Ratings [1]
Parameter
Min.
Max.
Unit
Voltage to Control VSWR, V1
0
1.6
V
Voltage to Control Attenuation, V2
0
1.6
V
RF Input Power, Pin
17
dBm
Operating Channel Temperature, Tch
+150
dB
+150
°C
300
°C
Storage Temperature, Tstg
Maximum Assembly Temperature, Tmax
-65
Comments
60 second maximum
Notes:
1. Operation in excess of any one of these conditions may result in permanent damage to this device. The absolute maximum ratings for V1, V2 and
Pin were determined at an ambient temperature of 25°C unless noted otherwise..
2
Typical Performance (TA = 25°C, Zin = Zout = 50 Ω)
0
Min+2dB
Min+4dB
20
Min+8dB
30
Min+12dB
Min+16dB
40
Min+20dB
Max
50
0
5
10
15
20
Frequency (GHz)
25
0
5
10
15
20
Frequency (GHz)
25
30
Figure 2. Input Return Loss vs Frequency
30
-10
25
20
-20
-30
-40
Min
Max
0
5
10
15
20
Frequency (GHz)
25
15
10
5
0
30
Figure 3. Output Return Loss vs Frequency
0
10
Attenuation (dB)
20
30
20
30
Figure 4. IIP3 vs Attenuation at 2 GHz (note 2)
30
25
25
20
20
IIP3 (dBm)
30
15
10
5
0
Min
Max
-40
-50
IIP3 (dBm)
Output Return Loss (dB)
-30
0
-50
IIP3 (dBm)
-20
30
Figure 1. Attenuation vs Frequency
15
10
5
0
10
20
Attenuation (dB)
Figure 5. IIP3 vs Attenuation at 12 GHz (note 2)
3
-10
Input Return Loss (dB)
10
Attenuation (dB)
0
Min
30
0
0
10
Attenuation (dB)
Figure 6. IIP3 vs Attenuation at 22 GHz (note 2)
0
0
Min
10
Min+4dB
Min+8dB
15
Min+12dB
20
Min+16dB
Min+20dB
25
Max
30
-10
-5
0
5
Input Power (dBm)
Min+8dB
20
Min+12dB
25
Min+16dB
30
Min+20dB
Max
-10
-5
0
5
Input Power (dBm)
10
Figure 8. Attenuation vs Input Power at 12 GHz
0
Min
5
Min+2dB
10
Min+4dB
15
Min+8dB
20
Min+12dB
25
Min+16dB
30
Min+20dB
-10
-5
0
5
Input Power (dBm)
Min+2dB
10
Min+4dB
15
Min+8dB
20
Min+12dB
25
Min+16dB
Min+20dB
30
Max
35
Min
5
Attenuation (dB)
Attenuation (dB)
Min+4dB
15
10
0
Max
35
-10
10
Figure 9. Attenuation vs Input Power at 22 GHz
-5
0
5
Input Power (dBm)
10
Figure 10. Attenuation vs Input Power at 32 GHz
0
0
2
-40C
25C
85C
10
Attenuation (dB)
Attenuation (dB)
Min+2dB
10
35
Figure 7. Attenuation vs Input Power at 2 GHz
4
6
-40C
25C
85C
8
10
Min
5
Min+2dB
Attenuation (dB)
Attenuation (dB)
5
0
5
10
15
20
Frequency (GHz)
Figure 11. Attenuation vs Frequency (Min Attenuation)
25
30
20
30
40
0
5
10
15
Frequency (GHz)
20
Figure 12. Attenuation vs Frequency (Max Attenuation)
Notes:
1. All tests done on an AMMP-6650 mounted on a PCB equipped with RF connectors and an op-amp driver shown in Figure 14.
2. IIP3 measured with two input signals with frequency difference of 10 MHz, each input signal at -10 dBm
3. All attenuation settings were done at 2GHz utilizing the AMMP-6650 DC Reference circuit. VREF was set to 0.1 volt.
4
25
30
AMMP-6650 Typical Scattering Parameters at Minimum Attenuation
(Tc = 25°C, Zo = 50ohm, V1 = 1.5V, V2 = 0V)
Freq
GHz
dB
S11
Mag
Phase
dB
S21
Mag
Phase
dB
S12
Mag
Phase
dB
S22
Mag
Phase
0.5
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
-26.02
-26.02
-22.73
-20.09
-18.34
-16.95
-16.03
-15.34
-14.8
-14.7
-14.47
-14.75
-14.85
-15.39
-15.92
-16.83
-17.86
-19.33
-21.11
-23.35
-27.33
-32.77
-31.7
-25.68
-21.62
-18.34
-16.48
-14.99
-14.33
-14.24
-14.47
-14.52
-14.99
-16.03
-17.72
-20.09
-22.5
-23.48
-21.41
-18.56
-16.36
-14.56
-13.11
-12.01
-11.28
-10.81
-10.57
-10.6
-10.78
-11.28
0.05
0.05
0.07
0.1
0.12
0.14
0.16
0.17
0.18
0.18
0.19
0.18
0.18
0.17
0.16
0.14
0.13
0.11
0.09
0.07
0.04
0.02
0.03
0.05
0.08
0.12
0.15
0.18
0.19
0.19
0.19
0.19
0.18
0.16
0.13
0.1
0.08
0.07
0.09
0.12
0.15
0.19
0.22
0.25
0.27
0.29
0.3
0.3
0.29
0.27
-39.1
-66.7
-93.5
-108
-120.3
-131.5
-140.9
-149.7
-157.5
-165.3
-172.9
-180
172.5
165.6
158.2
151
143.5
135.1
127.3
116.3
99.3
59.4
-19.1
-54
-71.5
-85.7
-100.6
-114.3
-127.7
-137.9
-147.1
-155.5
-164.2
-171.7
-177.3
-178
-166.3
-143.6
-122.9
-116.9
-118.7
-123.8
-130.9
-139.4
-148.9
-158.8
-169.5
-179.7
170.4
162.1
-1.13
-1.1
-1.13
-1.24
-1.31
-1.36
-1.42
-1.46
-1.52
-1.55
-1.62
-1.64
-1.68
-1.7
-1.73
-1.76
-1.78
-1.8
-1.81
-1.83
-1.86
-1.92
-2
-2.12
-2.23
-2.35
-2.38
-2.45
-2.5
-2.58
-2.65
-2.7
-2.73
-2.78
-2.83
-2.83
-2.95
-2.96
-3.01
-3.12
-3.25
-3.43
-3.69
-4.01
-4.34
-4.78
-5.26
-5.66
-6.14
-6.76
0.88
0.88
0.88
0.87
0.86
0.86
0.85
0.85
0.84
0.84
0.83
0.83
0.82
0.82
0.82
0.82
0.82
0.81
0.81
0.81
0.81
0.8
0.79
0.78
0.77
0.76
0.76
0.75
0.75
0.74
0.74
0.73
0.73
0.73
0.72
0.72
0.71
0.71
0.71
0.7
0.69
0.67
0.65
0.63
0.61
0.58
0.55
0.52
0.49
0.46
-5.8
-10.3
-19.2
-28.1
-36.9
-45.5
-54.2
-62.7
-71.3
-79.8
-88.4
-96.8
-105.4
-114.1
-122.8
-131.5
-140.3
-149.3
-158.4
-167.7
-176.9
173.5
163.9
154.2
144.6
135.4
126.8
118.8
110.1
101.1
91.5
82.3
73.2
63.3
53.1
42.8
32
21
9.9
-1.5
-13
-24.9
-36.8
-48.7
-60.5
-72.7
-84.2
-95.7
-107.7
-119.1
-1.15
-1.18
-1.23
-1.34
-1.43
-1.47
-1.55
-1.6
-1.65
-1.7
-1.74
-1.79
-1.82
-1.84
-1.85
-1.87
-1.88
-1.89
-1.92
-1.94
-1.96
-2.03
-2.09
-2.21
-2.35
-2.45
-2.5
-2.56
-2.59
-2.64
-2.69
-2.72
-2.77
-2.83
-2.88
-2.93
-2.96
-3.01
-3.09
-3.2
-3.31
-3.49
-3.76
-4.08
-4.42
-4.82
-5.29
-5.71
-6.23
-6.8
0.88
0.87
0.87
0.86
0.85
0.84
0.84
0.83
0.83
0.82
0.82
0.81
0.81
0.81
0.81
0.81
0.81
0.8
0.8
0.8
0.8
0.79
0.79
0.78
0.76
0.75
0.75
0.75
0.74
0.74
0.73
0.73
0.73
0.72
0.72
0.71
0.71
0.71
0.7
0.69
0.68
0.67
0.65
0.63
0.6
0.57
0.54
0.52
0.49
0.46
-5.8
-10.3
-19.2
-28.1
-36.9
-45.5
-54
-62.5
-71
-79.5
-88
-96.5
-105.1
-113.7
-122.4
-131.2
-139.9
-148.9
-158
-167.1
-176.5
174
164.4
154.7
145.2
136
127.3
119.2
110.6
101.6
91.9
82.8
73.8
63.9
53.7
43.3
32.7
21.8
10.6
-0.7
-12.2
-24.1
-36.1
-48.2
-59.7
-71.9
-83.5
-95.1
-107
-118.5
-26.2
-25.51
-22.62
-20.18
-18.56
-17.33
-16.36
-15.76
-15.24
-15.04
-14.94
-14.99
-15.34
-15.81
-16.42
-17.33
-18.64
-20.18
-22.16
-24.88
-28.64
-35.39
-37.72
-29.37
-24.44
-20.92
-18.49
-16.77
-15.86
-15.49
-15.65
-15.76
-16.14
-17.2
-18.86
-20.92
-23.48
-24.01
-21.62
-18.56
-16.31
-14.33
-12.69
-11.5
-10.66
-9.95
-9.47
-9.22
-9.14
-9
0.05
0.05
0.07
0.1
0.12
0.14
0.15
0.16
0.17
0.18
0.18
0.18
0.17
0.16
0.15
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0.01
0.03
0.06
0.09
0.12
0.15
0.16
0.17
0.17
0.16
0.16
0.14
0.11
0.09
0.07
0.06
0.08
0.12
0.15
0.19
0.23
0.27
0.29
0.32
0.34
0.35
0.35
0.36
-39.2
-60.2
-85.5
-102.1
-115.4
-127.6
-137.4
-146.5
-155
-163.3
-171.8
179.9
172.3
164.3
156.6
148.6
141.1
134
125.4
118.4
107.6
81.1
-23.8
-61.8
-73.2
-85.7
-98.5
-111
-123.6
-134.6
-144.9
-151.7
-160.2
-168.8
-174.7
-173.1
-162.3
-137.3
-117.7
-113.5
-115.9
-122
-130.4
-139.5
-149.8
-160.7
-171.9
176.6
165
152.8
Notes:
AMMP-6650 mounted on a PCB equipped with RF connectors and an op-amp driver shown in Figure 14.
5
AMMP-6650 Typical Scattering Parameters at Maximum Attenuation
(Measured on-wafer, Tc = 25°C, Zo = 50ohm, V1 = 0V, V2 = 1.25V)
Freq
GHz
dB
S11
Mag
Phase
dB
S21
Mag
Phase
dB
S12
Mag
Phase
dB
S22
Mag
Phase
0.5
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
-22.85
-22.5
-21.94
-20.82
-19.83
-19.02
-18.2
-17.46
-16.77
-16.36
-15.86
-15.49
-15.29
-15.19
-14.99
-15.04
-15.19
-15.34
-15.44
-15.7
-15.97
-16.14
-16.48
-16.95
-17.52
-18.06
-18.64
-19.33
-19.66
-20.54
-21.62
-22.73
-24.01
-25.51
-26.94
-27.54
-27.13
-25.85
-23.88
-22.16
-20.35
-19.25
-17.92
-17.14
-16.42
-15.76
-15.04
-14.29
-13.47
-12.04
0.07
0.08
0.08
0.09
0.1
0.11
0.12
0.13
0.15
0.15
0.16
0.17
0.17
0.17
0.18
0.18
0.17
0.17
0.17
0.16
0.16
0.16
0.15
0.14
0.13
0.13
0.12
0.11
0.1
0.09
0.08
0.07
0.06
0.05
0.05
0.04
0.04
0.05
0.06
0.08
0.1
0.11
0.13
0.14
0.15
0.16
0.18
0.19
0.21
0.25
-12.3
-21.6
-38.5
-53.4
-67
-78.6
-89
-98.9
-107
-114.6
-121.5
-127.9
-134.6
-140.7
-146.6
-151.7
-156.8
-162
-166.1
-170.4
-174.7
-178.9
176.4
170.7
166.5
164.2
159.6
154.9
149.9
144.5
135.2
126.4
118.1
103.6
81.6
58
33.7
12.4
-1.6
-16
-25.2
-32.1
-40.3
-46.9
-52.7
-57
-58
-58.8
-62.3
-67.5
-24.44
-24.44
-24.58
-24.44
-24.44
-24.29
-24.15
-24.01
-23.88
-23.74
-23.48
-23.35
-23.22
-23.1
-23.1
-22.97
-22.85
-22.97
-23.1
-23.48
-24.01
-24.44
-24.88
-25.35
-25.85
-26.2
-26.74
-27.33
-27.96
-28.18
-28.4
-28.87
-28.87
-29.12
-29.63
-29.9
-30.17
-30.75
-31.06
-31.7
-32.04
-32.4
-33.15
-33.98
-34.42
-34.89
-35.92
-36.48
-37.72
-38.42
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.06
0.06
0.06
0.05
0.05
0.05
0.05
0.04
0.04
0.04
0.04
0.04
0.04
0.04
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.01
0.01
-3.8
-6.7
-12.6
-18.5
-24.6
-30.8
-37.1
-44
-51.1
-58.5
-66.2
-74.1
-82.4
-91
-100
-109.5
-119.4
-130.1
-141.6
-153.4
-164.8
-174.2
178.2
172.3
167.1
164.2
159.2
154
146.1
137.2
127.3
120.3
112.8
104
95.5
86.6
77.8
69.3
61.3
53.2
45.6
36.2
27.5
18.7
10.3
-0.1
-10
-19.6
-29.1
-41.4
-24.58
-24.58
-24.58
-24.44
-24.44
-24.29
-24.15
-24.01
-23.88
-23.61
-23.48
-23.35
-23.22
-23.1
-22.97
-22.97
-22.85
-22.85
-23.1
-23.48
-23.88
-24.44
-24.88
-25.19
-25.68
-26.2
-27.13
-27.54
-27.74
-28.18
-28.4
-28.87
-28.87
-29.12
-29.37
-29.9
-30.17
-30.75
-31.37
-31.7
-32.04
-32.77
-33.15
-33.56
-34.42
-35.39
-35.92
-36.48
-37.72
-37.72
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.06
0.06
0.06
0.06
0.05
0.05
0.04
0.04
0.04
0.04
0.04
0.04
0.04
0.04
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.01
0.01
-3.7
-6.7
-12.7
-18.5
-24.7
-30.8
-37.2
-43.8
-50.9
-58.5
-66.1
-74.1
-82.3
-90.9
-100
-109.6
-119.4
-130.1
-141.7
-153.2
-164.8
-174.2
178.2
172.3
167
163.9
159
153.4
145.7
137.1
126.5
120.3
112.6
103.2
95.1
86.3
77
70.4
59.1
53.8
43.4
34.8
27.4
17.2
11.9
-2.9
-7.6
-18.6
-28.8
-37.8
-22.62
-22.5
-21.94
-21.01
-20.18
-19.25
-18.42
-17.65
-17.02
-16.48
-16.08
-15.76
-15.49
-15.34
-15.29
-15.24
-15.39
-15.55
-15.76
-15.92
-15.86
-15.92
-16.03
-16.14
-16.48
-16.83
-17.14
-17.59
-17.92
-18.56
-19.17
-20
-20.63
-21.31
-21.62
-21.83
-21.94
-21.62
-21.01
-20.45
-19.66
-18.79
-18.2
-17.86
-17.27
-16.89
-16.65
-15.92
-14.7
-13.56
0.07
0.08
0.08
0.09
0.1
0.11
0.12
0.13
0.14
0.15
0.16
0.16
0.17
0.17
0.17
0.17
0.17
0.17
0.16
0.16
0.16
0.16
0.16
0.16
0.15
0.14
0.14
0.13
0.13
0.12
0.11
0.1
0.09
0.09
0.08
0.08
0.08
0.08
0.09
0.1
0.1
0.12
0.12
0.13
0.14
0.14
0.15
0.16
0.18
0.21
-12.7
-21.4
-38
-53.6
-66.8
-78.9
-89.1
-98.2
-107
-115
-122.5
-129.7
-136.5
-142.7
-149.2
-154.9
-160.4
-165.3
-169.3
-172.9
-176.5
178.7
173.4
167.4
161.9
156.1
149.9
143.3
136.2
128.3
118.7
109.2
99.5
86.3
71.8
57.5
41.4
26.2
12.2
0.4
-11.7
-21.6
-29.8
-38
-44.2
-47.7
-49
-49.9
-51
-54.4
Notes:
AMMP-6650 mounted on a PCB equipped with RF connectors and an op-amp driver shown in Figure 14.
6
Biasing considerations
VREF RS
500
DCin
NC
DCout
1
2
3
DC
reference circuit
RFin
8
4
variable
attenuator
7
6
5
V1
NC
V2
RFout
Pin
1
2
3
4
5
6
7
8
NC
DCin
Function
DC in
NC
DC out
RF out
V2
NC
V1
RF in
DCout
RFin
RFout
V1
V2
NC
OP AMP 1
A +
B _
RL (500)
OP AMP 2
+ C
_ D
VCONTROL
R1 (10K)
Note : Package base : GND
500
RREF (620)
Figure 13. Bias voltage connections
Figure 14. AMMP-6650 and the op-amp driver circuit
Attenuation is controlled by applying voltage to pin V1
(Pin 7) and pin V2 (Pin5), as shown in Figure 13.
If optimum VSWR is all that is required, OP AMP 2 may be
eliminated however, RL must remain connected to the
DCout pad of the AMMP-6650 and the control voltage can
be applied directly to V2.
Top View
For the minimum attenuation, V1 is set to 1.5 V and V2
is set to 0 V. The 1.5 V applied to the V1 pin biases the
series FETs to a full “on” state, while the 0 V applied to the
V2 pin keeps the shunt FETs in an “off” or “open” state;
thus creating the lumped element 50 Ω transmission line
effect. The V2 voltage swing from 0 V to 1.25 V increases
the level of attenuation. The V1 voltage swing from 1.5 V
to 0 V effectively optimizes the input and output match at
higher attenuation levels. The AMMP-6650 can be driven
by two complementary voltage ramps placed on V1 and
V2. Careful adjustments of the two control lines over a
relatively small voltage ranges are required to set the attenuation and optimize VSWR.
The on-chip DC reference circuit can be used to optimize
VSWR for any attenuation setting, improve voltage versus
attenuation linearity and range, and provide temperature
compensation.
The on-chip DC reference circuit is a non-distributed “T”
attenuator designed to operate in a 500 Ω system and
track the control voltage versus attenuation characteristics of the RF attenuator. A simplified schematic of the
AMMP-6650 together with an op-amp driver that utilizes
the DC reference circuit is shown in Figure 14.
OP AMP 1 insures that the attenuator maintains a good
input and output match to 50 Ω, while OP AMP 2 increases
the usable control voltage range versus using only direct
voltage ramps for V1 and V2 and improves over temperature operation.
7
C1
R2 (100)
CAUTION: Low voltage op-amps must be used so as not to
exceed the maximum limit of V1 and V2 control voltages.
As shown, a voltage reference (VREF) is fed to the reference
circuit DCin pad via a 500 Ω resistor, creating a 500 Ω
source. The reference circuit termination RL, is connected
to the DCout pad and ideally is also equal to 500 Ω. This
voltage is controlled in parallel with the RF attenuator.
The chosen value of VREF must be low enough to avoid
modifying the FET biasing and lower than the turn-on
voltage of the ESD protection diode but high enough
such that the attenuated voltage at OP AMP 2 is usable
compared to input offsets etc. The optimum value for the
positive reference voltage is approximately 0.1 to 0.4 V.
At equilibrium, the voltages at nodes A and B of the
OP AMP 1 must be equal which implies that the input
impedance to the DC reference circuit is equal to RREF.
When V2 is changed to a lower value, the voltage at node
A becomes greater than that of node B. This voltage difference causes the output voltage of op OP AMP 1 to
move toward its positive rail until equilibrium is once
again established. When V2 is changed to a higher value
the voltage at node A becomes less than that of node B
and the output voltage of OP AMP 1 will swing toward its
negative rail until equilibrium is reached. If the reference
circuit precisely tracks the RF circuit, the voltage output
of OP AMP 1 at equilibrium insures that the RF circuit is
matched to 50 Ω.
If attenuation linearity is required, OP AMP 2 is included
as shown in Figure 14 and a positive control voltage is
applied to VCONTROL. At equilibrium, voltages at nodes C
and D are equal. When VCONTROL is changed, the output
of OP AMP 2 adjusts to a value that forces the voltage at
node C to equal the voltage at node D. Therefore, the
output voltage of the DC reference circuit is proportional
to VCONTROL. The input voltage to the reference circuit is
being held constant and the log(VCONTROL) is proportional
to the reference circuit attenuation 20log(DCout/DCin).
The voltage divider formed by R1 and R2 can be used
to adjust the sensitivity of the attenuator versus control
voltage. For the driver circuit shown in Figure 14, maximum
attenuation is always achieved by setting VCONTROL equal
to 0 V. Minimum attenuation is achieved when
If the FET parameters of the DC reference circuit track the
FET parameters of the RF circuit, the voltage output of the
RF circuit is also proportional to the control voltage. This
translates to a linear relationship between the attenuation
(in dB) and the log(VCONTROL).

R1
Vcontrol ≈ 1 +
R2

Due to the difference in layout structures, the reference
circuit does not track the RF circuit precisely. RL and RREF
can be adjusted in order to compensate for these differences. Optimum values of RL and RREF have been found
to be between 500 Ω and 650 Ω.
For maximum dynamic range on the attenuation control
circuit, RL should be less than RREF by an amount equal
to the “ON resistance” of the reference circuit series FETs.
The “ON resistance” of the series FETs is about 95 Ω total.
Therefore, the relationship between RL and RREF is as
follows:
RREF = RL + 95 Ω
8
or



x DCout
Therefore, an increase in the resistor ratio R1/R2 increases
the value of the control voltage required to produce
minimum attenuation.
LMV932 (National Semiconductor) was used in the control
circuit that produced the results shown in Figure 15;
however, any low noise, low offset voltage op amp should
produce similar results. LMV932’s low supply voltage of
1.8 volts, limits the possibility of exceeding the 1.5 volt
absolute maximum of the AMMC-6650 V1 and V2 control
line inputs.
Attenuation (dB)
Another way to improve performance of the attenuator driver circuit is to adjust RL and RREF . If the reference
circuit precisely tracked the RF circuit and the ON resistance of the FETs was zero ohms, then RL and RREF would
be exactly 500 Ω.



OP AMP 2 provides temperature compensation by adjusting
V2 in such a way as to keep voltage at point C equal to
that point D. If the attenuation changes over temperature, voltage at point C tries to change, but is corrected by
OP AMP 2.



Two RF attenuation vs voltage curves corresponding
to different values of VREF are shown in Figure 15. These
curves were obtained by using the driver circuit shown in
Figure 14 and the VREF values 0.1 V and 0.4 V. Values for
RL, R1 and R2 were 500 Ω, 10 kΩ and 100 Ω respectively.
Control voltage ranged from 4.5 V to 0 V.
Because the FETs in the DC circuit are not identical to
those in the RF circuit, the DC circuit does not exactly track
the RF circuit. This results in attenuation vs. voltage curves
that are not exactly linear.

RL
 R1 + R2
Vcontrol ≈ 
x
x Vref
500
Ω
+ RL
R2


0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
0.01
Vref=0.1V
Vref=0.2V
0.1
1
Control Voltage (Vin)
Figure 15. Attenuation vs. Control Voltage @ 15 GHz
10
Package Dimension, PCB Layout and Tape and Reel information
Please refer to Avago Technologies Application Note 5520, AMxP-xxxx production Assembly Process (Land Pattern A).
Ordering Information
Part Number
Devices Per
Container
Container
AMMP-6650-BLKG
10
Antistatic bag
AMMP-6650-TR1G
100
7” Reel
AMMP-6650-TR2G
500
7” Reel
For product information and a complete list of distributors, please go to our web site:
www.avagotech.com
Avago, Avago Technologies, and the A logo are trademarks of Avago Technologies in the United States and other countries.
Data subject to change. Copyright © 2005-2013 Avago Technologies. All rights reserved.
AV02-1337EN - July 8, 2013