Transcript
MGA-675T6 Wideband Low Noise Amplifier with Integrated Shutdown Function for 5-6 GHz Applications
Application Note 5387
Introduction
Pin Configuration and Biasing
This application note discusses the application of Avago Technologies’ MGA-675T6 for 5-6 GHz application. The MGA-675T6 is integrated internally with shutdown and biasing circuitry. Besides reducing the complexity of the external circuitry, the shutdown circuitry allows the LNA to be easily shut down by an external voltage control. This feature makes the MGA-675T6 suitable to be used in a mobile receiver where the amplifier can be switched off easily to reduce current consumption and to extend a battery life.
The MGA-675T6 is housed in an UTSLP (Ultra-thin Small Leadless Package) package with a very low profile (0.4 mm) and small footprint (2.0 x 1.3 mm2) that requires only a small area of printed circuit board. Figure 1 shows the simplified internal circuitry and pin configuration of the MGA-675T6.
By using Avago Technologies’ proprietary 0.5-micron GaAs E-pHEMT technology (Enhancement-mode pseudomorphic high electron mobility transistor), the MGA-675T6 can achieve excellent linearity, high gain and very low noise figure at low voltage and current. These are the key parameters to improve the sensitivity of the receiver. The low operating voltage and current is essential to modern portable devices such as notebook or mobile devices that are equipped with multiple wireless standards (WiMAX, WLAN, GPS, and Digital Television etc.). Simultaneous applications of these functions always require high power consumption, especially digital TV which heavily involves image display. Thus, great power efficiency to extend battery life becomes an important requirement for portable devices. While operating at 3 V and 10 mA, the MGA-675T6’s measured performance at 5.5 GHz on the demonstration board is typically: 1.75 dB NF, >17 dB gain, -3 dBm IIP3, and -9 dBm IP1dB. The device can be easily shut down through an external control voltage, and it will draw almost zero current (A range).
MGA-675T6 Vshutdown
RF_IN Not Connected
1
6 bias/control
2
5
3
4
Vdd
RF_OUT Not Connected
(Top View) Figure 1. Simplified Internal Circuitry and Pin Configuration
The integrated bias circuitry inside the MGA-675T6 simplifies the external biasing application circuit. Unlike a typical depletion-mode pHEMT, the enhancement-mode pHEMT LNA in the MGA-675T6 only requires a positive voltage supply to bias the LNA. In this design, Vdd (pin 6), RF_OUT (pin 5) and Vshutdown (pin 1) are supplied with +3 V. The device draws approximately 10 mA with a +3 V supply voltage in the amplifier mode, and the current drawn at the Vshutdown pin is <0.3 mA. When the device is operating in the shutdown mode, the Vdd and Vshutdown pins draw almost zero current (A range).
Integrated Shutdown Function 20
MGA-675T6
15 Vshutdown
Active Bias
10
Vdd
5
Gain, dB
Vshutdown ~ 13 k: RF_IN
RF_OUT
-5 Vdd=3.6 V
-10
Amplifier Path Biasing Path NC
0
-15
Vdd=3 V
-20
Vdd=2.7 V
-25
NC
0
1
2 Vshutdown, volts
3
4
Figure 2. Simplified Internal Circuitry
Figure 3. Gain versus Vshutdown (Frequency = 5.5 GHz)
Mobile devices always have limited battery life and thus require great power efficiency. A shutdown feature allows the amplifier to be turned off while not in use, and this will greatly improve the power efficiency. The MGA-675T6 features an integrated shutdown circuit. It can be easily
k shut down by leaving the Vshutdown pin open or applying 0 to 0.2 V to it while maintaining the Vdd at +3 V. Figure 3 shows the gain versus shutdown voltage plot at various Vdd voltages. The current drawn by both the Vdd and Vshutdown pins in the shutdown mode is almost zero.
5-6GHz Wideband Application Circuit for MGA-675T6 Vshutdown +3 V
Vdd +3 V C6 L2 C5
C4 R1 MGA-675T6 1 C1 RFin TL1
bias/control
C3
6 L1
2 3 NC
5
C2 RFout
4 NC
Figure 4. Application Circuit Schematic
Figure 4 shows the application circuit of the MGA-675T6 for 5-6 GHz. The input matching of the device is formed by a microstrip short-stub followed by a series capacitor, C1, to give a low noise figure and high gain over a very wide frequency range of 5 to 6 GHz. The input shunt short-stub (TL1) also helps to improve the ESD level at the RFin pin (pin 2). The output matching circuit is formed by an RF choke, L1, and a blocking capacitor, C2, for optimum gain and output return loss. Both C3 and C4 are functioning as bypass capacitors and matching components. 2
Resistor R1 and capacitor C5 are used to enhance the circuit’s stability and in addition provide RF grounding to any unwanted feedback through the power supply line from RFout (pin 5) to Vdd (pin 6). L2 is used to insert a biasing voltage to the device and also to isolate the device from the power supply. C6 is added as a low frequency bypass capacitor to avoid low frequency feedback through the power supply line. The C5, C6 and R1 components are considered to be optional components in the actual application.
Demonstration Board Performance
Table 1. RF Performance for the MGA-675T6 at 5.5 GHz
Table 1 summarizes the performance of the MGA-675T6 at 5.5 GHz. All the parameters are measured on the demonstration board shown in Figure 18a.
LNA Mode
The following plots show the noise figure, stability, gain, return loss, reverse isolation, forward isolation (shutdown mode) and linearity of the device on the demonstration board.
Stability Factor, k (30kHz – 20GHz) Vdd
V
+3
Current, Id
mA
10
Gain, S21
dB
17.6
Noise Figure, NF
dB
1.75
Input Return Loss, IRL
dB
>10
Output Return Loss, ORL
dB
>10
Reverse Isolation
dB
35
Input 3rd-order Intercept Point, IIP3*
dBm
-3.2
Input 1 dB Gain Compression Point, IP1dB
dBm
-9
Shutdown Voltage, Vshutdown
V
0
Forward Isolation at Shutdown mode
dB
-24
*
Test condition: FRF1 = 5.5 GHz, FRF2 = 5.505 GHz with input power of -30 dBm per tone measured at the worst case side band.
2.5 2.4 2.3
k factor and B1
Noise Figure, dB
2.2 2.1 2.0 1.9 1.8 1.7 1.6 1.5 4.9
5.0
5.1
5.2
5.3 5.4 5.5 5.6 Frequency, GHz
5.7
5.8
5.9
10 9 8 7 6 5 4 3 2 1 0
6.0
0
0
-4
-2
16
-8
14
-12
-20
Isolation
Return Loss, dB
Gain, dB
Gain
6
-28
4
-32
2
-36
-14
0
-40 6.0
-16
5.4
5.5
Frequency, GHz
5.6
5.7
8
10
14
16
18
20
5.8
5.9
Input Return Loss Output Return Loss
-10 -12
4.9
5.0 5.1 5.2
5.3 5.4 5.5 5.6 Frequency, GHz
Figure 7. Gain, Return Loss and Reverse Isolation over Frequency for the MGA-675T6 (narrowband) (Vdd=Vshutdown=+3 V)
3
12
-8
-24
5.3
6
-6
8
5.2
4
-4 Isolation, dB
-16
12
5.1
2
Figure 6. k factor and Stability Measure over Frequency for the MGA-675T6 (Vdd=Vshutdown=+3 V)
18
5.0
B1>0
0
20
4.9
k >1
Frequency, GHz
Figure 5. Noise Figure over Frequency for the MGA-675T6 (Vdd=Vshutdown=+3 V)
10
>1
5.7 5.8 5.9
6.0
30
0
10
-20
-10
-40
-30
-60
0
Gain Isolation
-50
Return Loss, dB
Isolation, dB
Gain, dB
-5 -10
4
6
8 10 12 14 Frequency, GHz
16
18
-25 -30 Input Return Loss Output Return Loss
-40 -45
-100 2
-20
-35
-80
-70 0
-15
0
20
2
4
6
8 10 12 Frequency, GHz
14
16
18
20
Figure 8. Gain, Return Loss and Reverse Isolation over Frequency for the MGA-675T6 (wideband) (Vdd=Vshutdown=+3 V)
2.0
0
0.0
-10 -15 IIP3, dBm
Forward Isolation, dB
-5
-20 -25 -30
-2.0 -4.0 -6.0
-35 -40 4.9
5.0
5.1 5.2 5.3 5.4 5.5 5.6 Frequency, GHz
-8.0 4.9
5.7 5.8 5.9 6.0
Figure 9. Forward Isolation over Frequency for the MGA-675T6 at Shutdown Mode (Vdd=+3 V; Vshutdown=0 V)
20
-2
18 16
-6
Gain, dB
P1dB, dBm
-4
-10 -12 -14 -16 4.9
5
5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 Frequency, GHz
Figure 11. Input P1dB over Frequency for the MGA-675T6 (Vdd=Vshutdown=+3 V)
4
6
5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6 Frequency, GHz
Figure 10. Input 3rd-order Intercept Performance over Frequency for the MGA-675T6 (Vdd=Vshutdown=+3 V)
0
-8
5
14 12 10 8 6
Vdd=3.6 V
4 2
Vdd=2.7 V
Vdd=3 V
0 0
1
2 Vshutdown, V
3
Figure 12. Gain versus Vshutdown versus Vdd for the MGA-675T6
4
0.0
12
- 0.5
10
- 1.0 IIP3, dBm
Idd, mA
14
8 6 4 2 1
- 2.5
Vdd=3 V
- 3.0
Vdd=2.7 V
- 3.5
3
2 Vshutdown, V
2.6
2.8
3
3.2
3.4
3.6
Vdd, V Figure 14. Input 3rd-order Intercept Point over Device Voltage for the MGA-675T6 (Vdd=Vshutdown) 0 -10 -20 Pout, dBm
P1dB, dBm
- 4.0
4
Figure 13 Device Current versus Vshutdown versus Vdd for the MGA-675T6
-7 -7.2 -7.4 -7.6 -7.8 -8 -8.2 -8.4 -8.6 -8.8 -9 2.6
- 2.0
Vdd=3.6 V
0 0
- 1.5
ON
OFF
-30 -40 -50 -60
2.8
3 Vdd, V
3.2
3.4
3.6
Figure 15. Input P1dB over Device Voltage for the MGA-675T6 (Vdd=Vshutdown)
0.0
0.5
1.0 1.5 Time, μs
2.0
2.5
Figure 16. Output Power versus Time (Switching Time) for the MGA-675T6 (Vdd=+3 V; Frequency=5.5 GHz; Pin=-25 dBm)
Turn-on and Turn-off Time Fast turn-on and turn-off time of the LNA is important for a TDD (Time Division Duplex) system. Figure 16 shows the time needed for the MGA-675T6 to switch ON or OFF. The MGA-675T6 needs <0.5 s time to switch from amplifier mode to shutdown mode or vice versa.
5
The switching time is measured by applying a 5.5 GHz CW signal at -25 dBm to the RF input and +3 V to the Vdd pin of the device. A square wave from 0V to +3 V with a period of 5 s is applied to the Vshutdown pin to switch the device. The +3 V switches the device to amplifier mode and 0 V switches the device to shutdown mode.
Sycn
Function Generator (Hewlett Packard 33120A) 200 kHz Square wave 3 Vp-p (0 V to 3 V)
Power Supply (Hewlett Packard 6623A)
Vshutdown Signal Generator 5.5 GHz, -25 dBm CW signal
RF In
Ext Trig In
+3 V DC Vdd MGA 675T6
RF Out
Spectrum Analyzer (Agilent PSA E4440A) Ext Ref In
10MHz Ref Out Figure 17. Measurement Setup for Turn-on and Turn-off Time of the MGA-675T6 LNA
Component Placement, Bill of Material and PCB Layout Table 2. Bill of Material for the MGA-675T6 Size
Value
Manufacturer
Part Number
Description
67
–
–
Avago
MGA-675T6
DUT
L1
0402
1 nH
TOKO
LL1005-FH1N0S
RF Choke/Output Matching
L2
0402
10 nH
TOKO
LL1005-FH10NJ
Isolation
TL1
Refer to Figure 12b for TL1 Dimensions
C1
0402
1.8 pF
Murata
Standard Ceramic Chip Capacitor
Input Matching
C2
0402
2 pF
Murata
Standard Ceramic Chip Capacitor
Blocking Capacitor/Output Matching
C3
0402
3 pF
Murata
Standard Ceramic Chip Capacitor
Bypass Capacitor /Output Matching
C4
0402
1.6 pF
Murata
Standard Ceramic Chip Capacitor
Bypass Capacitor/Inter-stage Matching
C5
0402
10 nF
Murata
Standard Ceramic Chip Capacitor
Bypass Capacitor
C6
0603
0.1 F
Murata
Standard Ceramic Chip Capacitor
Bypass Capacitor
R1
0402
10
Input Matching
Stability Enhancement
1
2
3
4
SD
IN
TL1 C4 C1
7F
C5 R1 C3 L1 C2
L1=148 mil
50 Ω
C6 L2
VD OUT
MGA-675T6 TC E07A FEB 07
10 mil diameter via hole
L2=105 mil
Board Material: Rogers RO4350 Dielectric Constant, R =3.48 DC Pin Configuration of 4-pin Connector Pin 1 –Vshutdown Pin 2,4 – Ground Pin 3 - Vdd
Figure 18a. Component Placement 6
Figure 18b. TL1 Dimensions
SD
MGA-675T6 TC E07A FEB 07
VD OUT
IN
Top Metal (Top View)
Inner Metal/RF Ground (Top View)
Bottom Metal (Top View)
Figure 19a. Demonstration Board Layout
0.5 oz. copper
Top
10 mil ROGERS RO4350
Inner
Total Thickness 60 mil (For mechanical strength) FR4 material/Prepreg (Support Material)
Bottom Figure 19b. PCB Stacking Structure
Summary The MGA-675T6 has good noise figure and high gain to improve the receiver’s sensitivity and to ensure a reliable data reception. The integral shutdown function enables the amplifiers to be shut down easily to reduce the power consumption. Low power consumption is important to the portable devices with limited battery life. In conclusion, the exceptional performance of the MGA-675T6 makes it a great choice to be used as the front-end amplifier of a portable receiver.
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 © 2005-2012 Avago Technologies. All rights reserved. AV02-1262EN - August 16, 2012
