19-4797; Rev 0; 2/99
UAL
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10MHz to 500MHz VCO Buffer Amplifiers
with Differential Outputs
The MAX2470/MAX2471 are flexible, low-cost, highreverse-isolation buffer amplifiers for applications with
discrete and module-based VCO designs. Both feature
differential 50Ω outputs for driving a single differential
(balanced) load or two separate single-ended (unbalanced) 50Ω loads. The MAX2470 offers a single-ended
input and has two selectable frequency ranges of operation: 10MHz to 500MHz and 10MHz to 200MHz. The
MAX2471 offers a differential input and operates from
10MHz to 500MHz. The MAX2470/MAX2471 also feature
high input impedance for maximum flexibility, enabling
them to be used with a variety of oscillator topologies.
High reverse isolation combined with low supply current
make them ideal for applications requiring high performance with low power.
These devices are also ideal for use as active baluns.
The MAX2470 converts a single-ended input to a differential output. The MAX2471 is useful as a differential
buffer stage or to convert from a differential input to two
single-ended outputs.
The MAX2470 operates from a single +2.7V to +5.5V
supply. At -5dBm output power, it consumes 5.5mA in
the high-frequency range and only 3.6mA in the
low-frequency range. The MAX2471 operates from a
+2.7V to +5.5V single supply and consumes 5.5mA.
Both devices are available in ultra-small SOT23-6 plastic packages, requiring minimal board space.
Features
♦ +2.7V to +5.5V Supply Range
♦ Input Frequency Range
High: 10MHz to 500MHz (MAX2470/2471)
Low: 10MHz to 200MHz (MAX2470)
♦ >14dB Power Gain at 200MHz
♦ 64dB Typical Reverse Isolation at 200MHz
♦ Low-Distortion Output Drive
♦ Ultra-Small SOT23-6 Package
♦ High Input Impedance
♦ Single-Ended (MAX2470) or Differential
(MAX2471) Inputs
Ordering Information
PART
TEMP. RANGE
PINPACKAGE
SOT TOP
MARK
MAX2470EUT-T
-40°C to +85°C
6 SOT23-6
AAAX
MAX2471EUT-T
-40°C to +85°C
6 SOT23-6
AAAY
Typical Operating Circuits
VCC
Applications
Cellular and PCS Mobile Phones
ISM-Band Applications
Active Baluns
General-Purpose Buffers/Amplifiers
HI/LO
MAX2470
BIAS
OUT
IN
50Ω
OUT
Pin Configuration
50Ω
GND
VCC
TOP VIEW
OUT 1
6
VCC
MAX2471
BIAS
GND 2
MAX2470
MAX2471
5
IN
4
HI/LO (IN)
OUT
IN
50Ω
OUT 3
SOT23-6
IN
OUT
GND
50Ω
( ) ARE FOR MAX2471
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX2470/MAX2471
General Description
MAX2470/MAX2471
10MHz to 500MHz VCO Buffer Amplifiers
with Differential Outputs
ABSOLUTE MAXIMUM RATINGS
VCC to GND ..............................................................-0.3V to +7V
IN to GND......-0.3V to (VCC + 0.3V) or 3.7V (whichever is lower)
IN to IN ..................................................................-2.2V to +2.2V
HI/LO to GND .............................................-0.3V to (VCC + 0.3V)
Continuous Power Dissipation
SOT23-6 (derate 8.7mW/°C above +70°C)...................696mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec ) ............................+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.
DC ELECTRICAL CHARACTERISTICS
(Typical Operating Circuit, VCC = +2.7V to +5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3V,
TA = +25°C.) (Note 1)
PARAMETER
Supply Voltage Range
Supply Current
SYMBOL
CONDITIONS
TYP
MAX
UNITS
5.5
V
No signal
5.1
7.4
HI/LO = VCC
POUT = -5dBm,
RLOAD = 100Ω diff.
5.5
No signal
No signal
3.0
HI/LO = GND
POUT = -5dBm,
RLOAD = 100Ω diff.
3.6
VCC
ICC
HI/LO Input Level High
VIH
HI/LO Input Level Low
VIL
HI/LO Input Bias Current
IIN
MIN
2.7
4.5
2.0
V
-10
VHI/LO = GND or VCC
mA
0.6
V
10
µA
AC ELECTRICAL CHARACTERISTICS—MAX2470
(VCC = +3V, HI/LO = VCC, all outputs are differentially measured between OUT and OUT driving a 50Ω load through a 180° hybrid,
TA = +25°C, unless otherwise noted.)
PARAMETER
Input Frequency Range
(Note 2)
SYMBOL
fIN
CONDITIONS
10
500
10
200
IS21I2
fIN = 10MHz
14.9
fIN = 200MHz
14.9
fIN = 500MHz,
TA = TMIN to TMAX
Noise Figure
2
NF
13.3
13.8
fIN = 200MHz
14.1
fIN = 10MHz, HI/LO = GND
RSOURCE = 50Ω
fOUT = 200MHz,
RHI/LO = GND
8.9
fIN = 10MHz
fIN = 200MHz,
TA = TMIN to TMAX
AV
MAX
HI/LO = GND
HI/LO = GND
Voltage Gain (Note 4)
TYP
HI/LO = VCC
HI/LO = VCC
Gain (Note 3)
MIN
9.9
13.4
16
fOUT = 500MHz,
HI/LO = VCC
10.2
fOUT = 200MHz,
RHI/LO = GND
10.2
UNITS
MHz
15.3
dB
15.0
V/V
dB
_______________________________________________________________________________________
10MHz to 500MHz VCO Buffer Amplifiers
with Differential Outputs
(VCC = +3V, HI/LO = VCC, all outputs are differentially measured between OUT and OUT driving a 50Ω load through a 180° hybrid,
TA = +25°C, unless otherwise noted.)
PARAMETER
Maximum Output VSWR
(OUT, OUT) (Note 5)
SYMBOL
VSWROUT
CONDITIONS
10MHz < fOUT < 200MHz, HI/LO = GND
1.2:1
IS12I2
HI/LO = GND
Isolation OUT to OUT
(Note 7)
Harmonic Suppression
TYP
1.5:1
HI/LO = VCC
Reverse Isolation
(Note 6)
MIN
10MHz < fOUT < 500MHz, HI/LO = VCC
fIN = 100MHz
75
fIN = 500MHz
48
fIN = 100MHz
75
fIN = 200MHz
64
fIN = 500MHz, HI/LO = VCC
37
fIN = 200MHz, HI/LO = GND
45
fIN = 500MHz, POUT = -5dBm, HI/LO = VCC
-26
fIN = 200MHz, POUT = -5dBm, HI/LO = GND
-30
MAX
UNITS
dB
dB
dBc
AC ELECTRICAL CHARACTERISTICS—MAX2471
(Typical values are measured at VCC = +3V, TA = +25°C, unless otherwise noted.) (Note 8)
PARAMETER
Input Frequency Range
(Note 2)
SYMBOL
CONDITIONS
fIN
MIN
10
fIN = 10MHz
IS21I2
Gain (Note 3)
TYP
UNITS
500
MHz
15.9
fIN = 200MHz
fIN = 500MHz, TA = TMIN to TMAX
MAX
16.9
11.3
15.6
dB
17.8
Voltage Gain (Note 4)
AV
fIN = 10MHz
16
V/V
Noise Figure
NF
fOUT = 500MHz, RSOURCE = 50Ω
8.4
dB
Maximum Output VSWR
(OUT, OUT) (Note 5)
VSWROUT
10MHz < fOUT < 500MHz
1.5:1
fIN = 100MHz
74
fIN = 500MHz
57
Isolation OUT to OUT (Note 7)
fIN = 500MHz
35
dB
Harmonic Suppression
fIN = 500MHz, POUT = -5dBm
-29
dBc
IS12I2
Reverse Isolation
dB
Note 1: Limits are 100% production tested at TA = +25°C. Limits over the entire operating temperature range are guaranteed by
design and characterization but are not production tested.
Note 2: The part has been characterized over the specified frequency range. Operation outside of this range is possible but not
guaranteed.
Note 3: Gain specified for POUT = -5dBm.
Note 4: Voltage gain measured with no input termination and no output load.
Note 5: Output VSWR is a single-ended measurement for each OUT and OUT.
Note 6: OUT to IN isolation with OUT terminated with 50Ω.
Note 7: Input terminated with 50Ω.
Note 8: Unless otherwise noted: all inputs are differentially measured between IN and IN driven by a 50Ω load through a 180°
hybrid; all outputs are differentially measured between OUT and OUT driving a 50Ω load through a 180° hybrid.
_______________________________________________________________________________________
3
MAX2470/MAX2471
AC ELECTRICAL CHARACTERISTICS—MAX2470 (continued)
Typical Operating Characteristics
(VCC = +3.0V, MAX2470 output and MAX2471 input and output measurements taken differentially, TA = +25°C, unless otherwise
noted.)
TA = +25°C
TA = +85°C
3.6
3.5
3.4
TA = -40°C
5.6
5.5
5.4
3.2
TA = +25°C
TA = +85°C
5.3
5.2
5.1
TA = -40°C
5.0
4.9
3.3
4.8
3.0
3.5
4.0
4.5
5.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
MAX2470/71-03
HI/LO = GND
fIN = 200MHz
HI/LO = VCC
fIN = 500MHz
-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10
SUPPLY VOLTAGE (V)
INPUT POWER (dBm)
MAX2470
TRANSDUCER GAIN vs. FREQUENCY
(HI/LO = GND)
MAX2470
TRANSDUCER GAIN vs. FREQUENCY
(HI/LO = VCC)
MAX2470
NOISE FIGURE vs. FREQUENCY
(HI/LO = GND)
15.0
17.0
12.0
MAX2470/71-05
TA = -40°C
TA = -40°C
16.0
HI/LO = GND
11.5
NOISE FIGURE (dB)
15.0
TA = +25°C
TA = +25°C
IS21I2 (dB)
13.0
TA = +85°C
12.0
14.0
12.0
10.0
11.0
9.0
HI/LO = GND
TA = +85°C
13.0
11.0
100
150
200
10.5
HI/LO = VCC
9.5
9.0
50
11.0
10.0
10.0
8.0
0
100
200
300
400
0
500
50
150
100
200
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
MAX2470
NOISE FIGURE vs. FREQUENCY
(HI/LO = VCC)
MAX2470
REAL INPUT IMPEDANCE vs. FREQUENCY
MAX2470
IMAGINARY INPUT IMPEDANCE vs. FREQUENCY
10,000
HI/LO = VCC
11.5
0
MAX2470/71-09
HI/LO = VCC
MAX2470/71-08
12.0
MAX2470/71-07
0
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
-11
-12
-13
-14
-15
-16
SUPPLY VOLTAGE (V)
16.0
14.0
5.5
MAX2470/71-04
2.5
HI/LO = VCC
-500
RE [ZIN] (Ω)
1000
11.0
IM [ZIN] (Ω)
IS21I2 (dB)
5.7
OUTPUT POWER (dBm)
3.7
-5dBm OUTPUT POWER
fIN = 500MHz
HI/LO = GND (MAX2470)
5.8
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
3.8
MAX2470
OUTPUT POWER vs. INPUT POWER
MAX2470/71-02
-5dBm OUTPUT POWER
fIN = 200MHz
HI/LO = GND
3.9
6.0
5.9
MAX2470/71-01
4.0
MAX2470 (HI/LO = VCC) AND MAX2471
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX2470/71-06
MAX2470
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(HI/LO = GND)
NOISE FIGURE (dB)
MAX2470/MAX2471
10MHz to 500MHz VCO Buffer Amplifiers
with Differential Outputs
100
-1000
-1500
-2000
10.5
10
10.0
1
0
100
200
300
FREQUENCY (MHz)
4
-2500
400
500
-3000
0
50 100 150 200 250 300 350 400 450 500
FREQUENCY (MHz)
0
100
200
300
FREQUENCY (MHz)
_______________________________________________________________________________________
400
500
10MHz to 500MHz VCO Buffer Amplifiers
with Differential Outputs
MAX2470
OUTPUT VSWR vs. FREQUENCY
1.25
OUT
OUT TO IN
60
50
40
100
200
300
400
500
MAX2470/71-12
0
-2
fIN = 200MHz
fIN = 500MHz
-4
-6
-8
-10
OUT TO OUT
INPUT TERMINATED IN 50Ω
-12
20
-14
0
100
200
300
400
-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10
500
FREQUENCY (MHz)
FREQUENCY (MHz)
INPUT POWER (dBm)
MAX2471
DIFFERENTIAL TRANSDUCER
POWER GAIN vs. FREQUENCY
MAX2471
NOISE FIGURE vs. FREQUENCY
MAX2471
REAL INPUT IMPEDANCE vs. FREQUENCY
TA = +85°C
16.0
8.25
NOISE FIGURE (dB)
16.5
TA = -40°C
15.5
10,000
MAX2470/71-15
17.0
8.50
1000
RE [ZIN] (Ω)
TA = +25°C
MAX2470/71-14
17.5
MAX2470/71-13
0
8.00
7.75
100
15.0
10
7.50
14.0
1
7.25
50 100 150 200 250 300 350 400 450 500
0
0
50 100 150 200 250 300 350 400 450 500
50 100 150 200 250 300 350 400 450 500
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
MAX2471
IMAGINARY INPUT IMPEDANCE
vs. FREQUENCY
MAX2471
OUTPUT VSWR vs. FREQUENCY
MAX2471
OUTPUT ISOLATION vs. FREQUENCY
1.50
MAX2470/71-16
500
IM [ZIN] (Ω)
OUTPUT VSWR
0
INPUT TERMINATED
SINGLE-ENDED MEASUREMENT
VSWR OUT
1.25
90
OUTPUT ISOLATION (dB)
0
VSWR OUT
-500
80
SINGLE-ENDED
MEASUREMENT
70
OUT TO IN
MAX2470/71-18
14.5
MAX2470/71-17
TRANSDUCER POWER GAIN (dB)
2
MAX2470/71-11
OUT TO IN
70
30
1.00
MAX2471
OUTPUT POWER vs. INPUT POWER
OUTPUT POWER (dBm)
OUT
HI/LO = VCC
SINGLE-ENDED
MEASUREMENT
80
OUTPUT ISOLATION (dB)
HI/LO = VCC
INPUT TERMINATED IN 50Ω
SINGLE-ENDED MEASUREMENT
OUTPUT VSWR
90
MAX2470/71-10
1.50
MAX2470
OUTPUT ISOLATION vs. FREQUENCY
60
50
40
OUT TO OUT
30
INPUT TERMINATED IN 50Ω
1.00
-1000
0
100
200
300
FREQUENCY (MHz)
400
500
20
0
100
200
300
FREQUENCY (MHz)
400
500
0
100
200
300
400
500
FREQUENCY (MHz)
_______________________________________________________________________________________
5
MAX2470/MAX2471
Typical Operating Characteristics (continued)
(VCC = +3.0V, MAX2470 output and MAX2471 input and output measurements taken differentially, TA = +25°C unless otherwise
noted.)
10MHz to 500MHz VCO Buffer Amplifiers
with Differential Outputs
MAX2470/MAX2471
Pin Description
PIN
NAME
FUNCTION
1
OUT
Differential Noninverting Buffer Output. Broadband 50Ω output. AC coupling is required.
Do not DC couple to this pin.
2
2
GND
RF Ground. Connect to the ground plane as close as possible to the IC to minimize
ground path inductance.
3
3
OUT
Differential Inverting Buffer Output. Broadband 50Ω output. AC coupling is required. Do
not DC couple to this pin.
4
—
HI/LO
Bias and Bandwidth Control Input. Connect to VCC to set internal bias for higher bandwidth operation (10MHz to 500MHz). Connect to GND to set internal bias for lower bandwidth operation (10MHz to 200MHz) and to reduce overall current consumption.
—
4
IN
Differential Inverting Buffer Input. High impedance input to buffer amplifier. See Setting
The Input Impedance section.
5
5
IN
Differential Noninverting Buffer Input. High impedance to buffer amplifier. See Setting The
Input Impedance section.
6
6
VCC
MAX2470
MAX2471
1
Supply Voltage Input. +2.7V < VCC < +5.5V.
_______________ Detailed Description
Bandwidth Control Circuitry
The MAX2470 features a logic-controlled bias circuit
which optimizes the performance for input frequencies
from 10MHz to 500MHz (HI/LO = VCC) and 10MHz to
200MHz (HI/LO = GND). Operating with HI/LO = GND
significantly reduces power consumption.
__________ Applications Information
Input Considerations
The MAX2470/MAX2471 offer high-impedance inputs,
ideal for low-distortion buffering of a VCO. For applications with discrete transistor-based oscillator designs,
simply AC-couple the oscillator directly to the inputs.
The buffer’s high input impedance results in minimal
loading on the oscillator. For still higher real input
impedance and reduced loading effects, match the
inputs with a shunt-L matching circuit followed by a
series blocking capacitor. For use with 50Ω VCO modules, terminate the buffer input(s) with a 50Ω shunt
resistor followed by a series-blocking capacitor. This
provides a very stable 50Ω termination and increases
reverse isolation. For those applications needing both
high gain and good input match, reactively match the
buffer inputs to 50Ω with simple two-element matching
circuits followed by a series blocking capacitor.
6
Output Considerations
The MAX2470 and MAX2471 incorporate fully differential output stages capable of driving an AC-coupled
100Ω differential load or two AC-coupled 50Ω singleended loads. This is ideal for applications that require
the oscillator to drive two application circuits (e.g. mixer
and PLL) simultaneously. The high output-to-output isolation ensures minimal interaction between multiple
load circuits.
Layout and Power-Supply Bypassing
A properly designed PC board is essential to any RF/
microwave circuit. Be sure to use controlled impedance
lines on all high-frequency inputs and outputs. Bypass
the power supply with decoupling capacitors as close to
the VCC pins as possible. For long VCC lines (inductive), it
may be necessary to add additional decoupling capacitors located further away from the device package.
Proper grounding of GND is essential. If the PC board
uses a topside RF ground, connect GND directly to it.
For a board where the ground plane is not on the component side, the best technique is to connect GND to
the board with a plated through-hole (via) to the ground
plane close to the package.
_______________________________________________________________________________________
10MHz to 500MHz VCO Buffer Amplifiers
with Differential Outputs
TRANSISTOR COUNT: 67
6LSOT.EPS
Package Information
_______________________________________________________________________________________
7
MAX2470/MAX2471
Chip Information
MAX2470/MAX2471
10MHz to 500MHz VCO Buffer Amplifiers
with Differential Outputs
NOTES
8
_______________________________________________________________________________________
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