Download MAX3524 Low-Noise, High-Linearity Broadband Amplifier General Description

19-1764; Rev 2; 6/05
Low-Noise, High-Linearity
Broadband Amplifier
Features
The MAX3524 broadband amplifier is designed specifically for cable television receiver and cable modem
applications. The MAX3524 is a single-ended input, differential-output low-noise amplifier (LNA) that offers
15dB of gain. It operates from a +4.75V to +5.25V single supply from 44MHz to 880MHz. The MAX3524
includes an operational amplifier that is used to control
an off-chip PIN attenuator circuit at the input of the LNA.
The attenuator is typically used to regulate the input
signal to a value that maintains high linearity for large
signals. The MAX3524 is available in a 10-pin µMAX®
package with an exposed paddle (EP) and operates in
the extended temperature range (-40°C to +85°C).
♦ Single-Ended Input, Differential Output
♦ +4.75V to +5.25V Single-Supply Operation
♦ Broadband Operation: 44MHz to 880MHz
♦ Low Noise Figure: 4.2dB
♦ High Linearity: IIP2 (42dBm), IIP3(14dBm)
♦ Voltage Gain: 15dB
♦ Independent On-Chip Op Amp
Ordering Information
Applications
Cable Modems
TEMP RANGE
PIN-PACKAGE
Cable Set-Top Boxes
MAX3524EVB
PART
-40°C to +85°C
10 µMAX-EP*
Broadband Amplifiers
MAX3524EVB+
-40°C to +85°C
10 µMAX-EP*
CATV Infrastructures
*EP = Exposed paddle.
+Denotes lead-free package.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Typical Application Circuit
VCC = 5V
10µF
INPUT:
44-880MHz
75Ω TO 2kΩ
1
0.1µF
2
PIN
ATTENUATOR
RFOUT- 10
VCC
RFIN
MAX3524
VCC
0.1µF
L1 = 0.5nH TO 1nH
CL < 1.8pF
OUTPUT TO TUNER
(DIFFERENTIAL DRIVE)
9
VCC = 5V
10µF
10nF
0.1µF
3
4
8
RFGND
L2 = 0.5nH TO 1nH
RFOUT+
OPIN+
OPOUT
7
0.1µF
R1
3kΩ
FROM DEMOD IC
TO CONTROL PIN
ATTENUATOR
OP AMP
D2
CMDSH-3
5
OPIN-
BIAS
GND
R2
3kΩ
6
LBIAS = 680nH
RBIAS = 5.9Ω
*
D1
CMDSH-3
*EXPOSED PADDLE
Pin Configuration appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products
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1
MAX3524
General Description
MAX3524
Low-Noise, High-Linearity
Broadband Amplifier
ABSOLUTE MAXIMUM RATINGS
VCC to GND ...........................................................-0.3V to +7.0V
RFIN ....................................................................................+2.0V
PRFIN ...................................................................................0dBm
RBIAS (MINIMUM) .......................................................................5Ω
RFOUT+, RFOUT-, OPIN-, OPIN+, OPOUT...-0.3V to (VCC + 0.3V)
RFOUT+, RFOUT- Short-Circuit Duration ...............................10s
Continuous Power Dissipation (TA = +70°C)
10-Pin µMAX (derate 10.3mW/°C above +70°C) .........825mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature ......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
CAUTION! ESD SENSITIVE DEVICE
DC ELECTRICAL CHARACTERISTICS
(Typical Application Circuit, VCC = +4.75V to +5.25V, RBIAS = 5.9Ω, LBIAS = 680nH, TA = -40°C to +85°C, unless otherwise indicated. Typical values measured at VCC = +5.0V, TA = +25°C.) (Notes 1, 2)
PARAMETERS
CONDITIONS
MIN
TYP
MAX
UNITS
SUPPLY
Supply Voltage
4.75
Supply Current
5.25
V
95
mA
3.0
V
85
OPERATIONAL AMPLIFIER
Common-Mode Input Range
0.5
Maximum Output Voltage
IO = 20mA
Minimum Output Voltage
IO = 20mA
VCC - 0.5
V
0.5
V
AC ELECTRICAL CHARACTERISTICS
(MAX3524 EV kit as shown in Figure 1, VCC = +4.75V to +5.25V, PRFIN = -20dBm, ZS = 75Ω, RBIAS = 5.9Ω, LBIAS = 680nH,
fIN = 44MHz, ZL = 50Ω || 2pF, TA = +25°C. Typical values are at VCC = +5V, unless otherwise indicated.) (Notes 2, 3)
PARAMETERS
CONDITIONS
Operating Frequency Range
Power Gain (Note 4)
MIN
TYP
44
TA = +25°C
8.0
TA = -40°C to +85°C
7.6
MAX
UNITS
880
MHz
9.8
11
11.5
Voltage Gain (Note 5)
RL = 3kΩ
15
Noise Figure (Note 3)
fRFIN = 300MHz
4.2
dB
dB
4.9
dB
IIP3 (Notes 3, 6)
12
14
dBm
IIP2 (Notes 3, 6)
40
42
dBm
40
60
dB
Output-to-Input Isolation
fRFIN = 300MHz
Note 1: Parameters are production tested at TA = +25°C and TA = +85°C. Limits are guaranteed by design and characterization for
TA = -40°C to +25°C.
Note 2: For optimum linearity, the DC resistance of LBIAS in series with RBIAS must be approximately 7.3Ω.
Note 3: Guaranteed by design and characterization.
Note 4: Gain is guaranteed over the operating frequency range, by design and characterization. Insertion loss of balun is subtracted.
Production tested at 44MHz and 880MHz.
Note 5: Corresponding voltage gain at RL = 3kΩ, calculated as in Figure 2.
Note 6: Frequencies and input power levels: 275MHz, 325MHz, and -20dBm per tone.
2
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Low-Noise, High-Linearity
Broadband Amplifier
(MAX3524 EV kit as shown in Figure 1, VCC = +5V, PRFIN = -20dBm, ZL = 50Ω || 2pF, RBIAS = 5.9Ω, LBIAS = 680nH, insertion loss of
balun subtracted, TA = +25°C.)
POWER GAIN vs. FREQUENCY
Zs = 50Ω
CL = 1.5pF
TA = -45°C
TA = +25°C
10
GAIN (dB)
87
86
TA = +25°C
TA = +85°C
9
TA = +85°C
7
40 140 240 340 440 540 640 740 840 940
40 140 240 340 440 540 640 740 840 940
VCC (V)
FREQUENCY (MHz)
FREQUENCY (MHz)
10
9
GAIN (dB)
VCC = 4.75, 5.00, 5.25
8
7
7
6
VCC = 4.75, 5.00, 5.25
9
8
MAX3524 toc06
TA = +85°C
5
4
TA = +25°C
3
TA = -40°C
2
1
0
6
40 140 240 340 440 540 640 740 840 940
40 140 240 340 440 540 640 740 840 940
40 140 240 340 440 540 640 740 840 940
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
IIP3 vs. FREQUENCY
IIP2 vs. FREQUENCY
1dB COMPRESSED OUTPUT POWER
vs. FREQUENCY
TA = -40°C
Zs = 75Ω
55
POUT (dBm)
IIP2 (dBm)
TA = +25°C
45
12
40
10
35
VCC = 5.25V
12
50
TA = +85°C
14
TA = +85°C
16
TA = +25°C
16
MAX3524toc09
18
60
MAX3524 toc07
Zs = 75Ω
MAX3524 toc08
GAIN (dB)
TA = +25°C
Zs = 75Ω
CL = 1.5pF
NOISE FIGURE (dB)
11
6
MAX3524 toc05
MAX3524 toc04
TA = +25°C
Zs = 50Ω
CL = 1.5pF
NOISE FIGURE vs. FREQUENCY
POWER GAIN vs. FREQUENCY
12
10
IIP3 (dBm)
6
4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5
POWER GAIN vs. FREQUENCY
14
TA = +85°C
7
6
82
20
TA = +25°C
10
8
83
11
TA = -40°C
11
9
8
84
12
Zs = 75Ω
CL = 1.5pF
12
TA = -40°C
85
13
GAIN (dB)
88
11
POWER GAIN vs. FREQUENCY
14
MAX3524 toc03
MAX3524toc01
89
ICC (mA)
12
MAX3524 toc02
CURRENT vs. VOLTAGE
90
TA = -40°C
10
8
VCC = 4.75V VCC = 5.00V
8
6
4
30
50 150 250 350 450 550 650 750 850 950
FREQUENCY (MHz)
100 200 300 400 500 600 700 800 900 1000
FREQUENCY (MHz)
40 140 240 340 440 540 640 740 840 940
FREQUENCY (MHz)
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3
MAX3524
Typical Operating Characteristics
Typical Operating Characteristics (continued)
(MAX3524 EV kit as shown in Figure 1, VCC = +5V, PRFIN = -20dBm, ZL = 50Ω || 2pF, RBIAS = 5.9Ω, LBIAS = 680nH, insertion loss of
balun subtracted, TA = +25°C.)
ISOLATION vs. FREQUENCY
PSRR vs. FREQUENCY
MAX3524toc11
-45
-45
-50
-50
-55
-55
PSRR (dB)
ISOLATION (dB)
-40
MAX3524toc10
-40
-60
-60
-65
-65
-70
-70
-75
-75
-80
-80
40
440
240
640
840
20
ZIN = R II C
OP AMP CLOSED-LOOP VOLTAGE GAIN
OF 2 vs. FREQUENCY
2.5
6
350
5
CAPACITANCE
150
1.5
4
VGAIN (dB)
2.0
250
CAPACITANCE (pF)
RESISTANCE
200
220
MAX3524 toc13
MAX3524 toc12
300
170
FREQUENCY (MHz)
RESISTANCE AND CAPACITANCE
vs. FREQUENCY
400
120
70
FREQUENCY (MHz)
RESISTANCE (Ω)
MAX3524
Low-Noise, High-Linearity
Broadband Amplifier
3
2
100
1
50
1
0
40
240
440
640
0
840
0
FREQUENCY (MHz)
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
FREQUENCY (MHz)
Pin Description
4
PIN
NAME
FUNCTION
1, 9
VCC
Supply Voltage Input. Connect both pins together. Bypass with a 10µF and 47pF capacitor to
GND.
2
RFIN
RF Input of LNA. Requires DC blocking capacitor.
3
RFGND
Bypass to GND through 10nF capacitor.
4
OPOUT
Operational Amplifier Output
5
OPIN-
Inverting Input of Operational Amplifier
6
BIAS
LNA Bias Setting Pin. For nominal bias, connect 5.9Ω resistor in series with 680nH to GND
(total DC resistance = resistance of RBIAS + DC resistance of the inductor = 7.3Ω). The value of
the resistor is adjusted to alter the current and therefore linearity of the LNA.
7
OPIN+
Noninverting Input of Operational Amplifier
8
RFOUT-
Inverting Output of LNA
10
RFOUT+
Slug
GND
Noninverting Output of LNA
Ground
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Low-Noise, High-Linearity
Broadband Amplifier
The MAX3524 is a broadband amplifier with a singleended input and differential outputs, including an operational amplifier that can be used to control an external
attenuator circuit. Figure 1 is the MAX3524 EV kit
schematic.
Low-Noise Amplifier
The low-noise amplifier operates from 44MHz to
880MHz and is designed specifically for cable TV and
cable modem applications. The LNA provides 15dB of
insertion voltage gain (see Figure 2) when driving a
3kΩ load. At 300MHz, the noise figure is 4.2dB, IIP2
and IIP3 are 42dBm and 14dBm, respectively.
Operational Amplifier
The operational amplifier is suitable for interfacing to a
PIN attenuator circuit which is typically employed at the
input of the LNA. The common-mode input range is
0.5V to 3V and the output voltage swing is 0.5V to VCC 0.5V while sinking or sourcing 20mA. Input bias current
and input offset voltage are 1µA and 1mV, respectively.
The open-loop voltage gain is greater than 10,000. The
gain bandwidth product is greater than 1MHz for a
closed-loop voltage gain of one.
VCC
C15
0.1µF
C1
47pF
R1
13.3Ω
C10
RF INPUT 0.1µF
VCC
R2
C11
0.1µF
RF OUTPUT
C14
47pF
C15
0.1µF
VCC2
C2
2pF
RF OUT+
R4
50kΩ
C12
0.1µF
VCC
RFIN
VCC
TO
ATTENUATOR
RF OUT-
RFGND
R3
50kΩ
R9
100Ω
OPIN+
0.1µF
OP OUT
R10
3kΩ
BIAS
D1
OP IN
R8
3kΩ R7
10kΩ
D2
LBIAS
VCC
RBIAS
5.81Ω
D1, D2 SMALL-SIGNAL SCHOTTKY DIODES, TYPICALLY CMDSH-3
Figure 1. MAX3524 EV Kit Schematic
VCC (PIN9)
75Ω
RFIN
AV = (VRFOUT +) - (VRFOUT-) = 5.7
VIN
AV(dB) = 20log10 AV = 15dB
V1
ZS
330Ω
2VIN
1.8pF
30Ω
30Ω
RFOUT+
0.06V1
RFOUT-
Figure 2. LNA Equivalent Circuit and Open-Circuit Voltage Gain Calculation
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5
MAX3524
Detailed Description
MAX3524
Low-Noise, High-Linearity
Broadband Amplifier
Table 1. Shunt-Resistor Noise-Figure
Values
RSHUNT(Ω)
S11(LNA) (dB)
NOISE FIGURE (dB)
450
-6
5 to 5.5
250
-8
5.5 to 6
125
-10
6 to 6.5
Applications Information
Bias Current
The resistor, RBIAS, connected between BIAS and GND
controls the LNA current. To make the current insensitive to temperature fluctuations, select a 1%, low temperature coefficient resistor for R BIAS . The current
drawn by the LNA is calculated using the following formula:
IBIAS ≈ 0.58V / (RBIAS + DC resistance of LBIAS)
It is important to include the inductor resistance in the
above equation as it is typically 1Ω to 2Ω. The
MAX3524 EV kit uses a nominal inductor with DC resistance of 1.4Ω. Higher values of RBIAS may be used to
reduce supply current predominantly at the expense of
linearity. Circuit board layout and source impedance
may require the value of IBIAS to be optimized for best
linearity.
RF Input Power Control Using the
Operational Amplifier
In a cable system, the power level at the LNA input is
typically restricted to a maximum value to maintain linearity. This is accomplished by connecting a variable
attenuator at the input of the LNA and varying the attenuation with the operational amplifier output. The operational amplifier receives a DC control input that is
proportional to LNA output power. See Typical
Application Circuit.
Layout Issues
A properly designed PC board is essential to any
RF/microwave circuit. Use short interconnect and controlled impedance lines on all high-frequency inputs
and outputs. Use low inductance connections to
ground on all GND nodes and place decoupling
capacitors close to all VCC connections. The EP is the
ground for the MAX3524 and must be soldered to
ground for proper operation.
Pin Configuration
TOP VIEW
VCC 1
Input and Output
RFIN
The LNA input is single-ended. The RF input signal is
coupled to RFIN through a DC blocking capacitor. The
LNA outputs drive a differential load, such as a mixer,
through DC blocking capacitors. The equivalent input
LNA impedance is 330Ω resistive in parallel with 1.8pf,
as shown in Figure 2. The approximate equivalent differential output impedance of the LNA is 60Ω. To
achieve S11 less than -6dB, an insertion loss of greater
than 1dB must exist between the cable input and
MAX3524. This loss typically comes from a diplexer
and PIN attenuator in a cable modem application. A
shunt resistor may be added at the input of the LNA to
improve the return loss (S11). Typically the return loss
of the system is 2dB better, as explained above. The
S11 and noise-figure values for different shunt resistors
are given in Table 1.
RFGND
3
OPOUT
OPIN-
6
10 RFOUT+
2
9
VCC
8
REFOUT-
4
7
OPIN+
5
6
BIAS
MAX3524
µMAX
Chip Information
TRANSISTOR COUNT: 550
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Low-Noise, High-Linearity
Broadband Amplifier
10LUMAX.EPS
e
4X S
10
10
INCHES
H
fl 0.50–0.1
0.6–0.1
1
1
0.6–0.1
BOTTOM VIEW
TOP VIEW
D2
MILLIMETERS
MAX
DIM MIN
0.043
A
0.006
A1
0.002
A2
0.030
0.037
0.120
D1
0.116
0.118
D2
0.114
0.120
E1
0.116
E2
0.114
0.118
H
0.187
0.199
L
0.0157 0.0275
L1
0.037 REF
0.0106
b
0.007
e
0.0197 BSC
c
0.0035 0.0078
0.0196 REF
S
α
0¡
6¡
MAX
MIN
1.10
0.05
0.15
0.75
0.95
2.95
3.05
2.89
3.00
2.95
3.05
2.89
3.00
4.75
5.05
0.40
0.70
0.940 REF
0.177
0.270
0.500 BSC
0.090
0.200
0.498 REF
0¡
6¡
E2
GAGE PLANE
A2
c
A
b
A1
α
E1
L
D1
L1
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, 10L uMAX/uSOP
APPROVAL
DOCUMENT CONTROL NO.
21-0061
REV.
I
1
1
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 7
© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
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MAX3524
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)