MAX2470 查看數據表（PDF） - Maxim Integrated

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MAX2470

10MHz to 500MHz VCO Buffer Amplifiers with Differential Outputs

Maxim Integrated 

10MHz to 500MHz VCO Buffer Amplifiers

with Differential Outputs

PIN

MAX2470 MAX2471

1

1

2

2

3

3

4

—

—

4

5

5

6

6

NAME

OUT

GND

OUT

HI/LO

IN

IN

VCC

Pin Description

FUNCTION

Differential Noninverting Buffer Output. Broadband 50Ω output. AC coupling is required.

Do not DC couple to this pin.

RF Ground. Connect to the ground plane as close as possible to the IC to minimize

ground path inductance.

Differential Inverting Buffer Output. Broadband 50Ω output. AC coupling is required. Do

not DC couple to this pin.

Bias and Bandwidth Control Input. Connect to VCC to set internal bias for higher band-

width operation (10MHz to 500MHz). Connect to GND to set internal bias for lower band-

width operation (10MHz to 200MHz) and to reduce overall current consumption.

Differential Inverting Buffer Input. High impedance input to buffer amplifier. See Setting

The Input Impedance section.

Differential Noninverting Buffer Input. High impedance to buffer amplifier. See Setting The

Input Impedance section.

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 applica-

tions 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 mod-

ules, 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.

Output Considerations

The MAX2470 and MAX2471 incorporate fully differen-

tial output stages capable of driving an AC-coupled

100Ω differential load or two AC-coupled 50Ω single-

ended 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 iso-

lation 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 capaci-

tors 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 com-

ponent 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.

6 _______________________________________________________________________________________

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