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19-1764; Rev 0; 7/00
Low-Noise, High-Linearity Broadband Amplifier
General Description
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 MAX package with an exposed paddle (EP) and operates in the extended temperature range (-40C to +85C).
Features
o Single-Ended Input, Differential Output o +4.75V to +5.25V Single-Supply Operation o Broadband Operation: 44MHz to 880MHz o Low Noise Figure: 4.2dB o High Linearity: IIP2 (42dBm), IIP3(14dBm) o Voltage Gain: 15dB o Independent On-Chip Op Amp
MAX3524
Applications
Cable Modem Cable Set-Top Box Broadband Amplifier CATV Infrastructure
VCC = 5V 10F 0.1F
Ordering Information
PART MAX3524EVB TEMP. RANGE -40C to +85C PIN-PACKAGE 10 MAX-EP*
*Exposed paddle
Typical Application Circuit
1
VCC
RFOUT-
10
L1 = 0.5 TO 1nH CL < 1.8pF OUTPUT TO TUNER (DIFFERENTIAL DRIVE) VCC = 5V 10F
INPUT: 44-880MHz 75-2k
0.1F PIN ATTENUATOR 2
RFIN
MAX3524
VCC
9
10nF
0.1F 3 RFGND OPOUT OP AMP 8 RFOUT+ OPIN+ 7
L2 = 0.5 TO 1nH
4 R1 3k D2 CMDSH-3
0.1F
FROM DEMOD IC TO CONTROL PIN ATTENUATOR
5
OPINGND *
BIAS
6 RBIAS = 5.9
LBIAS = 680nH
R2 3k D1 CMDSH-3
*EXPOSED PADDLE
Pin Configuration appears at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Low-Noise, High-Linearity Broadband Amplifier MAX3524
ABSOLUTE MAXIMUM RATINGS
VCC to GND ...........................................................-0.3V to +7.0V RFIN ....................................................................................+2.0V PRFIN ...................................................................................0dBm RBIAS (MINIMUM) .......................................................................5 RFOUT+, RFOUT-, OPIN-, OPIN+, OPOUT...-0.3V to (VCC + 0.3V) RFOUT+, RFOUT- Short-Circuit Duration ...............................10s Continuous Power Dissipation (TA = +70C) 10-Pin MAX (derate 10.3mW/C above +70C) .........825mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+150C Lead Temperature (soldering, 10s) .................................+300C
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.
DC ELECTRICAL CHARACTERISTICS
(Typical Application Circuit, VCC = +4.75V to +5.25V, RBIAS = 5.9, LBIAS = 680nH, TA = -40C to +85C, unless otherwise indicated. Typical values measured at VCC = +5.0V, TA = +25C.) (Notes 1, 2)
PARAMETERS SUPPLY Supply Voltage Supply Current OPERATIONAL AMPLIFIER Common-Mode Input Range Maximum Output Voltage Minimum Output Voltage IO = 20mA IO = 20mA 0.5 VCC - 0.5 0.5 4.75 85 5.25 95 3.0 V mA V V V CONDITIONS MIN TYP MAX UNITS
AC ELECTRICAL CHARACTERISTICS
(MAX3524 EV kit as shown in Figure 1, VCC = +4.75V to +5.25V, PRFIN = -20dBm, ZS = 75, RBIAS = 5.9, LBIAS = 680nH, fIN = 44MHz, ZL = 50 || 2pF, TA = +25C. Typical values are at VCC = +5V, unless otherwise indicated.) (Notes 2, 3)
PARAMETERS Operating Frequency Range Power Gain (Note 4) Voltage Gain (Note 5) Noise Figure (Note 3) IIP3 (Notes 3, 6) IIP2 (Notes 3, 6) Output-to-Input Isolation fRFIN = 300MHz TA = +25C TA = -40C to +85C RL = 3k fRFIN = 300MHz 12 40 40 CONDITIONS MIN 44 8.0 7.6 15 4.2 14 42 60 4.9 9.8 TYP MAX 880 11 11.5 UNITS MHz dB dB dB dBm dBm dB
Note 1: Parameters are production tested at TA = +25C and TA = +85C. Limits are guaranteed by design and characterization for TA = -40C to +25C. Note 2: For optimum linearity, the DC resistance of LBIAS in series with RBIAS must be approximately 7.3. 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 = 3k, 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
Typical Operating Characteristics
(MAX3524 EV kit as shown in Figure 1, VCC = +5V, PRFIN = -20dBm, ZL = 50 || 2pF, RBIAS = 5.9, LBIAS = 680nH, insertion loss of balun subtracted, TA = +25C.)
CURRENT vs. VOLTAGE
MAX3524toc01
MAX3524
POWER GAIN vs. FREQUENCY
MAX3524 toc02
POWER GAIN vs. FREQUENCY
13 12 Zs = 75 CL = 1.5pF
MAX3524 toc03
90 89 88 ICC (mA) 87 86 85 84 TA = +85C 83 82 TA = +25C TA = -40C
12 11 10 GAIN (dB) 9 8 7 6
Zs = 50 CL = 1.5pF TA = -45C TA = +25C TA = +85C
14
GAIN (dB)
11 10 9 8 7 6
TA = -40C TA = +25C TA = +85C
4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 VCC (V)
40 140 240 340 440 540 640 740 840 940 FREQUENCY (MHz)
40 140 240 340 440 540 640 740 840 940 FREQUENCY (MHz)
POWER GAIN vs. FREQUENCY
MAX3524 toc04
POWER GAIN vs. FREQUENCY
TA = +25C Zs = 75 CL = 1.5pF
MAX3524 toc05
NOISE FIGURE vs. FREQUENCY
TA = +85C 5 NOISE FIGURE (dB) 4 TA = +25C 3 2 1 0 TA = -40C
MAX3524 toc06
12 11 10 GAIN (dB) 9 8 7 6
TA = +25C Zs = 50 CL = 1.5pF
12 11 10 GAIN (dB)
6
VCC = 4.75, 5.00, 5.25
VCC = 4.75, 5.00, 5.25
9 8 7 6
40 140 240 340 440 540 640 740 840 940 FREQUENCY (MHz)
40 140 240 340 440 540 640 740 840 940 FREQUENCY (MHz)
40 140 240 340 440 540 640 740 840 940 FREQUENCY (MHz)
IIP3 vs. FREQUENCY
MAX3524 toc07
IIP2 vs. FREQUENCY
Zs = 75
MAX3524 toc08
1dB COMPRESSED OUTPUT POWER vs. FREQUENCY
MAX3524toc09
20 18 16 IIP3 (dBm)
Zs = 75 TA = -40C
60 55
16 14 12 VCC = 5.25V
TA = +85C TA = +25C 45 40 35 30 TA = -40C POUT (dBm) 50 IIP2 (dBm)
14 12 10 8
TA = +25C
TA = +85C
10 8 VCC = 4.75V VCC = 5.00V 6 4
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
Low-Noise, High-Linearity Broadband Amplifier MAX3524
Typical Operating Characteristics (continued)
(MAX3524 EV kit as shown in Figure 1, VCC = +5V, PRFIN = -20dBm, ZL = 50 || 2pF, RBIAS = 5.9, LBIAS = 680nH, insertion loss of balun subtracted, TA = +25C.)
ISOLATION vs. FREQUENCY
MAX3524toc10
PSRR vs. FREQUENCY
-45 -50 PSRR (dB) -55 -60 -65 -70 -75 -80
MAX3524toc11
-40 -45 -50 ISOLATION (dB) -55 -60 -65 -70 -75 -80 40 240 440 640 840 FREQUENCY (MHz)
-40
20
70
120
170
220
FREQUENCY (MHz)
RESISTANCE AND CAPACITANCE vs. FREQUENCY
400 350 300 RESISTANCE () 250 200 150 1.5 100 50 0 40 240 440 640 840 FREQUENCY (MHz) 1 1 0 CAPACITANCE RESISTANCE CAPACITANCE (pF) 2.0 VGAIN (dB)
MAX3524 toc12
OP AMP CLOSED-LOOP VOLTAGE GAIN OF 2 vs. FREQUENCY
MAX3524 toc13
ZIN = R II C
2.5
6 5 4 3 2
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
FREQUENCY (MHz)
Pin Description
PIN 1, 9 2 3 4 5 6 7 8 10 Slug NAME VCC RFIN RFGND OPOUT OPINBIAS OPIN+ RFOUTRFOUT+ GND FUNCTION Supply Voltage Input. Connect both pins together. Bypass with a 10F and 47pF capacitor to GND. RF Input of LNA. Requires DC blocking capacitor. Bypass to GND through 10nF capacitor. Operational Amplifier Output Inverting Input of Operational Amplifier LNA Bias Setting Pin. For nominal bias, connect 5.9 resistor in series with 680nH to GND (total DC resistance = resistance of RBIAS + DC resistance of the inductor = 7.3). The value of the resistor is adjusted to alter the current and therefore linearity of the LNA. Noninverting Input of Operational Amplifier Inverting Output of LNA Noninverting Output of LNA Ground
4
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Low-Noise, High-Linearity Broadband Amplifier
Detailed Description
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. insertion voltage gain (see Figure 2) when driving a 3k load. At 300MHz, the noise figure is 4.2dB, IIP2 and IIP3 are 42dBm and 14dBm, respectively.
MAX3524
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 1A and 1mV, respectively. The open-loop voltage gain is greater than 10,000. The
C15 0.1F
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
VCC C1 47pF C10 RF INPUT 0.1F R1 13.3 VCC R2 TO C11 ATTENUATOR 0.1F R9 100 C12 0.1F R4 50k RFGND R3 50k VCC RFIN
RF OUTVCC VCC2 RF OUT+
C14 47pF C15 0.1F
RF OUTPUT C2 2pF
OPIN+ OP OUT 0.1F
R10 3k BIAS D1 OP IN R8 3k R7 10k D2 VCC LBIAS RBIAS 5.81 D1, D2 SMALL-SIGNAL SCHOTTKY DIODES, TYPICALLY CMDSH-3
Figure 1. MAX3524 EV Kit Schematic
VCC (PIN9) 75 ZS 330 2VIN 30 RFIN V1
AV = (VRFOUT +) - (VRFOUT-) = 5.7 VIN AV(dB) = 20log10 AV = 15dB
1.8pF
30 RFOUT+ 0.06V1 RFOUT-
Figure 2. LNA Equivalent Circuit and Open-Circuit Voltage Gain Calculation _______________________________________________________________________________________ 5
Low-Noise, High-Linearity Broadband Amplifier MAX3524
Table 1. Shunt-Resistor Noise-Figure Values
RSHUNT() 450 250 125 S11(LNA) (dB) -6 -8 -10 NOISE FIGURE (dB) 5-5.5 5.5-6 6-6.5
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.
gain bandwidth product is greater than 1MHz for a closed-loop voltage gain of one.
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 1 to 2. The MAX3524 EV kit uses a nominal inductor with DC resistance of 1.4. 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.
Pin Configuration
TOP VIEW
VCC 1 RFIN RFGND OPOUT OPIN2 3 4 5 10 RFOUT+ 9 VCC REFOUTOPIN+ BIAS
MAX3524
8 7 6
Input and Output
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 330 resistive in parallel with 1.8pf, as shown in Figure 2. The approximate equivalent differential output impedance of the LNA is 60. 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.
MAX
Chip Information
TRANSISTOR COUNT: 550
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
6 _______________________________________________________________________________________
Low-Noise, High-Linearity Broadband Amplifier
Package Information
10LUMAX.EPS
MAX3524
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 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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