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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.
x 5 x 5 mm Surface Mount Package x Wide Frequency Range DC - 30 GHz x Attenuation Range 20dB x Single Positive Bias Supply x Unconditionally Stable
Applications x Microwave Radio Systems x Satellite VSAT, DBS Up / Down Link
Package Diagram
x LMDS & Pt – Pt mmW Long Haul
DCin
NC
DCout
1
2
3
x Broadband Wireless Access (including 802.16 and 802.20 WiMax) x 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
RoHS-Exemption 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. Please refer to hazardous substances table on page 9.
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 :) 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
Min Max
-40
0
5
10
15 20 Frequency (GHz)
25
30
Figure 2. Input Return Loss vs Frequency
0
30
-10
25 20 IIP3 (dBm)
-20 -30 -40
Min Max
15 10 5 0
0
5
10
15 20 Frequency (GHz)
25
30
0
10
20
30
20
30
Attenuation (dB)
Figure 3. Output Return Loss vs Frequency
Figure 4. IIP3 vs Attenuation at 2 GHz (note 2)
30
30
25
25
20
20 IIP3 (dBm)
IIP3 (dBm)
-30
-50
-50
15 10
15 10 5
5
0
0 0
10
20 Attenuation (dB)
Figure 5. IIP3 vs Attenuation at 12 GHz (note 2)
3
-20
30
Figure 1. Attenuation vs Frequency
Output Return Loss (dB)
-10 Input Return Loss (dB)
10 Attenuation (dB)
0
Min
30
0
10 Attenuation (dB)
Figure 6. IIP3 vs Attenuation at 22 GHz (note 2)
0
0 Min
5
Min+4dB Min+8dB
15
Min+12dB 20
Min+16dB
Attenuation (dB)
Attenuation (dB)
10
Min+20dB
25
Max
30 -10
-5
0 5 Input Power (dBm)
Min+4dB
15
Min+8dB
20
Min+12dB
25
Min+16dB
30
Min+20dB Max -10
10
-5
0 5 Input Power (dBm)
10
Figure 8. Attenuation vs Input Power at 12 GHz
0
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+2dB
10
35
Figure 7. Attenuation vs Input Power at 2 GHz
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
5
Min+2dB
4 6 -40C 25C 85C
8
20
30 40
10 0
5
10 15 20 Frequency (GHz)
Figure 11. Attenuation vs Frequency (Min Attenuation)
25
30
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 DCin 1
NC
VREF RS 500 NC
DCout
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
DCin
Function DC in NC DC out RF out V2 NC V1 RF in
DCout
RFin
RL (500)
RFout
V1
V2 NC
OP AMP 1 A + B _
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 : 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 :, 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
R2 (100) C1
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 : resistor, creating a 500 : source. The reference circuit termination RL, is connected to the DCout pad and ideally is also equal to 500 :. 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 :.
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 : and 650 :. 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 : total. Therefore, the relationship between RL and RREF is as follows: RREF = RL + 95 :
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 :.
§ ¨ ©
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 :, 10 k: and 100 : 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 :+ 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
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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
Names and Contents of the Toxic and Hazardous Substances or Elements in the Products
Part Name
Toxic and Hazardous Substances or Elements Lead (Pb) (Pb)
Mercury (Hg) Hg
Cadmium (Cd) Cd
Hexavalent (Cr(VI)) Cr(VI)
Polybrominated biphenyl (PBB) PBB
100pF capacitor : indicates that the content of the toxic and hazardous substance in all the homogeneous materials of the part is below the concentration limit requirement as described in SJ/T 11363-2006. : indicates that the content of the toxic and hazardous substance in at least one homogeneous material of the part exceeds the concentration limit requirement as described in SJ/T 11363-2006. (The enterprise may further explain the technical reasons for the “x” indicated portion in the table in accordance with the actual situations.)
SJ/T 11363-2006 SJ/T 11363-2006 “×” Note: EU RoHS compliant under exemption clause of “lead in electronic ceramic parts (e.g. piezoelectronic devices)”
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Avago, Avago Technologies, and the A logo are trademarks of Avago Technologies in the United States and other countries. Data subject to change. Copyright © 2005-2011 Avago Technologies. All rights reserved. AV02-1337EN - August 19, 2011
Polybrominated diphenylether (PBDE) PBDE