Analog-Devices-Inc–Maxim-Integrated-MAX2607EUT

Part #	Analog-Devices-Inc–Maxim-Integrated-MAX2607EUT
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19-1673; Rev 0a; 4/02

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

General Description

Features

The MAX2605–MAX2609 are compact, high-performance

intermediate-frequency (IF) voltage-controlled oscillators

(VCOs) designed specifically for demanding portable

wireless communication systems. They combine monolith-

ic construction with low-noise, low-power operation in a

tiny 6-pin SOT23 package.

ꢀ

Small Size

ꢀ

Integrated Varactor for Tuning

ꢀ

Low Phase Noise

ꢀ

Wide Application Frequency Range

ꢀ

Differential or Single-Ended Outputs

ꢀ

Single +2.7V to +5.5V Supply

ꢀ

Ultra-Small SOT23-6 Package

ꢀ

On-Chip Temperature-Stable Bias

ꢀ

Low-Current Operation

These low-noise VCOs feature an on-chip varactor and

feedback capacitors that eliminate the need for external

tuning elements, making the MAX2605–MAX2609 ideal

for portable systems. Only an external inductor is

required to set the oscillation frequency. In addition, an

integrated differential output buffer is provided for dri-

ving a mixer or prescaler. The buffer output is capable

of supplying up to -8dBm (differential) with a simple

power match. It also provides isolation from load

impedance variations.

The MAX2605–MAX2609 operate from a single +2.7V to

+5.5V supply and offer low current consumption. These IF

oscillators can cover the 45MHz to 650MHz frequency

range.

Ordering Information

PIN-

TOP

PART

TEMP. RANGE

PACKAGE MARK

MAX2605

EUT-T

MAX2606

EUT-T

MAX2607

EUT-T

MAX2608

EUT-T

MAX2609

EUT-T

-40°C to +85°C

6 SOT23-6

AABB

AABC

AABD

AABE

AABF

Applications

Cellular and PCS Mobile Phones

2.4GHz ISM Band

902MHz to 928MHz ISM Band

Land Mobile Radio

GPS Receivers

General-Purpose IF Oscillators

Pin Configuration/

Functional Diagram

Selector Guide

FREQUENCY

RANGE

SUPPLY

CURRENT

(mA)

PHASE

NOISE

(dBc/Hz)

TOP VIEW

PART

(MHz)

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

45 to 70

70 to 150

150 to 300

300 to 500

500 to 650

1.9

2.1

2.7

3.6

-117

-112

-107

-100

-93

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

IND

GND

OUT+

TUNE

OUT-

SOT23-6

________________________________________________________________

Maxim Integrated Products

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

ABSOLUTE MAXIMUM RATINGS

IND to GND …………………………………………-0.6V to (V

TUNE to GND ………………………………………-0.3V to (V

OUT+, OUT- to GND …………………………….-0.3V to (V

to GN

…………………………………………………….-0.3V to +6V

Operating Temperature Range ………………………-40°C to +85°C

Junction Temperatur

……………………………………………..+150°C

Storage Temperature Rang

……………………….-65°C to +150°C

Lead Temperature (soldering, 10s) ……………………………+300°C

+ 0.3V)

+ 0.6V)

Continuous Power Dissipation (T

= +85°C)

6-Pin SOT23 (derate

8.7

mW/°C above +70°C

)

……….696mW

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

= +2.7V to +5.5V, V

= 0.4V to 2.4V, T

= -40°C to +85°C, unless otherwise noted. Typical values are at V

= +2.75V,

TUNE

= 1.5V, and T

= +25°C.) (Note1)

TUNE

PARAMETER

CONDITIONS

MIN

TYP

1.9

2.1

2.7

3.6

MAX

5.5

2.6

2.8

2.7

3.0

3.2

3.5

4.4

5.5

6.8

7.5

1.5

UNITS

Supply Voltage

2.7

= +25°C

MAX2605

MAX2606

MAX2607

MAX2608

= -40°C to +85°C

= +25°C

= -40°C to +85°C

= +25°C

Supply Current (Note 2)

= -40°C to +85°C

= +25°C

= -40°C to +85°C

= +25°C

MAX2609

= -40°C to +85°C

DC Output Current (Note 3)

TUNE Input Current

OUT+ plus OUT-

0.5

1.0

0.03

_______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

AC ELECTRICAL CHARACTERISTICS

(MAX2605–MAX2609 EV kits, V

= +2.7V to +5.5V, V

= 0.4V to 2.4V, T

= -40°C to +85°C, unless otherwise noted. Typical val-

TUNE A

ues are at V

= +2.75V, V

= 1.5V, and T

= +25°C.) (Note 1)

TUNE A

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

150

Oscillator Nominal Frequency

Range (Note 4)

150

300

500

-4.1

-2.25

-4.4

-2.5

-4.6

-2.75

-4.7

-2.8

-5.0

-3.0

300

MHz

500

650

= +25°C

+3.2

+2.25

+3.4

+2.5

+3.6

+2.75

+3.6

+2.8

+3.8

+3.0

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

= -40°C to +85°C

= +25°C

= -40°C to +85°C

= +25°C

Guaranteed Frequency Limits

(relative to nominal) (Note 5)

= -40°C to +85°C

= +25°C

= -40°C to +85°C

= +25°C

= -40°C to +85°C

Peak Tuning Gain

= 0.4V to 0.6V step (Note 6)

14.5

-10

%/V

TUNE

Single-Ended Output Power

(Note 7)

dBm

MAX2605, Q

≥

-117

-112

-107

-100

-93

MAX2606, Q

≥

Phase Noise (Note 8)

= 100kHz

MAX2607, Q

≥

dBc/Hz

OFFSET

MAX2608, Q

≥

MAX2609, Q

≥

_______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

AC ELECTRICAL CHARACTERISTICS (continued)

(MAX2605–MAX2609 EV kits, V

= +2.7V to +5.5V, V

= 1.5V, and T

= +25°C.) (Note 1)

= 0.4V to 2.4V, T

= -40°C to +85°C, unless otherwise noted. Typical val-

TUNE A

ues are at V

= +2.75V, V

TUNE A

PARAMETER

CONDITIONS

MIN

TYP

-30

MAX

UNITS

Even-Order Harmonics

Differential, R

= 50

Ω

each side

dBc

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

120

220

480

720

Supply Pushing (Note 9)

kHz/V

Note 1:

Production tested at T

= +25°C. Maximum and minimum over temperature limits are guaranteed by design and

characterization.

Note 2:

Supply current is measured while the part is oscillating and inductor Q

≥

. For MAX2605/MAX2606/MAX2607, Q

= 35;

MIN

for MAX2608/MAX2609, Q

= 40.

MIN

Note 3:

The DC output current is the total available output signal current.

Note 4:

Application range of the part is achieved using external inductance as specified in Figures 1-5 and shown in Figure 6. The inter-

nal varactors support center frequencies of 45MHz to 650MHz. The center frequency is defined by the value of the external

inductor element, L

. The application frequency limits are guaranteed by design and characterization.

Note 5:

The guaranteed (tested) limits ƒ

and ƒ

are measured at V

= 0.4V and V

= 2.4V, respectively. Passing

MIN

MAX

TUNE

requirements are: ƒ

≤

at V

= 0.4 and ƒ

≥

at V

= 2.4V. The nominal frequency of oscillation is defined by

MIN

TUNE

MAX

TUNE

the inductor.

Note 6:

Describes peak tuning gain, which occurs at V

= 0.4V.

TUNE

Note 7:

Measurement at OUT+ or OUT- matched for optimum power transfer into 50

Ω

load near the center of the operating frequency

range.

Note 8:

The phase-noise specifications listed apply to the typical operating circuit shown in Figure 6. Apply over the entire operating

frequency range of the MAX2605–MAX2609.

Note 9:

Supply pushing is measured with V

stepped from +2.7V to +3.2V.

pical Operating Characteristics

(MAX260_ EV kit, V

= +2.75V, V

= 1.4V, T

= +25°C, unless otherwise noted.)

TUNE

MAX2605

VCO TUNING CURVE

SUPPLY CURRENT

vs. TEMPERATURE

TUNE INPUT LEAKAGE CURRENT

vs. TEMPERATURE

4.0

0.10

0.08

0.06

0.04

0.02

3.5

MAX2609

MAX2608 MAX2607

MAX2606

3.0

2.5

2.0

1.5

1.0

MAX2605

0.5

1.0

1.5

2.0

2.5

3.0

-40

-20

-40

-20

(V)

TEMPERATURE (°C)

TEMPERATURE (

TUNE

_______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

pical Operating Characteristics (continued)

(MAX260_ EV kit, V

= +2.75V, V

= 1.4V, T

= +25°C, unless otherwise noted.)

TUNE

MAX2607

VCO TUNING CURVE

MAX2606

VCO TUNING CURVE

130

MAX2608

VCO TUNING CURVE

260

430

400

370

340

310

240

220

200

180

160

120

110

100

0.5

1.0

1.5

2.0

2.5

3.0

0.5

1.0

1.5

2.0

2.5

3.0

0.5

1.0

1.5

2.0

2.5

3.0

(V)

TUNE

MAX2609

VCO TUNING CURVE

OUTPUT SPECTRUM

680

640

600

560

520

480

-10

-20

-30

-40

-50

0.5

1.0

1.5

2.0

2.5

3.0

2f 3f 4f

5f 6f 7f

o o o

(V)

FREQUENCY

TUNE

Pin Description

NAME

FUNCTION

Tuning Inductor Port. Connect an inductor from IND to GND to set VCO center frequency (see

Oscillation

Frequency

IND

GND

Ground. Connect to the ground plane with a low-inductance path.

TUNE

Voltage-Control Input for Frequency Tuning. Input voltage range from +0.4V to +2.4V.

High-Impedance Open-Collector Output. An external pull-up resistor or inductor to V

power is dependent on external load impedance. OUT- is complementary to OUT+.

is required. Output

OUT-

Supply Voltage Connection. Connect an external bypass capacitor to ground for low noise and low spuri-

ous-output content. See

Layout Issues

for more details.

High-Impedance Open-Collector Output. An external pull-up resistor or inductor to V

power is dependent on external load impedance. OUT+ is complementary to OUT-.

is required. Output

OUT+

_______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

that required for L

. Choose L

to be a standard-value

Detailed Description

inductor with a value ꢀust less than (L

– L

). L

The MAX2605–MAX2609 are low-noise VCOs designed

for fixed/single-frequency IF applications. The core

oscillator circuit is based on the well-known Colpitts

topology. The varactor and feedback capacitors are

integrated on-chip so that only an external inductor is

required to establish the frequency of oscillation and

produce a properly operating VCO. The tuning range,

biasing, startup, etc., are all managed within the IC. This

highly integrated design dramatically simplifies the

parts’ application.

should adhere to the minimum Q requirements, but L

may be implemented as a lower-cost, lower-Q, thin-film

SMT inductor. Its lower Q has only a small impact on

the overall Q of the total inductance because it is <20%

of the total inductance. However, the overall Q of L

and L

must be greater than the minimum inductor Q

(Table 1).

It is also permissible to use PC board traces to provide

a small amount of inductance, thereby adꢀusting the

total inductance value. On the MAX2608/MAX2609, the

The tuning range is wide enough so that, with the use

of 2%

tolerance inductors, no board-level adꢀustments

to the oscillation frequency are necessary. Once the

correct inductor value is chosen, the VCO is guaran-

teed always to tune to the desired operating frequency.

In addition, with the use of inductors of moderate Q (35

to 40), the VCO achieves excellent phase-noise perfor-

mance.

inductance values for L

are sometimes more exactly

implemented as a PC board trace (shorted to GND),

rather than an SMT inductor. When designing L

with

two inductors, use the simple model in Figure 7 to cal-

culate X

and L

The L

in Figures 1–5 represents an equivalent induc-

tance as seen by pin 1 (IND). The equivalent induc-

tance corresponds to the inductive reactance

connected to IND at the desired oscillation frequency

Applications Information

NOMINAL

Desired Oscillation Frequency

The desired VCO operating frequency is set by the

= X

/ (2

) as seen in Figure 8

NOMINAL

value of the external inductance, L . Figures 1–5 show

Design L

= L

at the desired f

. The

NOMINAL

the inductance value L

required to achieve the desired

MAX2605–MAX2609 are designed to tolerate approxi-

mately 0.5pF of external parasitic capacitance at IND.

This parasitic capacitance arises from the pad capaci-

tance at the device pin and pads for the inductor.

Additional shunt capacitance is not recommended

because it degrades the tuning range.

oscillation frequency. The inductor value can be taken

directly from these figures. Inductance must be select-

ed accurately to ensure proper operation over all con-

ditions.

Inductor Implementation

The inductance value required for the desired operat-

ing frequency may not necessarily coincide with a stan-

dard-value SMT inductor, which typically increases size

in ~1.2x steps. In such cases, the inductance must be

Bypass Capacitor on TUNE

The MAX2605–MAX2609’s oscillator design uses a vari-

ant of the Colpitts topology, where DC bias for the var-

actor is applied via a DC voltage on TUNE and a

ground connection through the external inductor L .

TUNE must also have a high-frequency AC ground for

constructed from two inductors, L

and L

, in order to

achieve the desired inductance value. Choose L

be a standard-value inductor with a value ꢀust less than

Table 1. External Inductor L

Range

Table 2. C

Values

BYPASS

FREQUENCY INDUCTANCE

MIN

INDUCTOR

PART

RANGE

(MHz)

RANGE

(nH)

DEVICE

BYPASS

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

45 to 70

70 to 150

150 to 300

300 to 500

500 to 650

680

≤

2200

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

≥

820 pF

≥

680 pF

≥

330 pF

≥

100 pF

≥

39 pF

150

≤

820

≤

180

≤

3.9

≤

_______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

MAX2605

REQUIRED INDUCTANCE vs. DESIRED VCO FIXED FREQUENCY

1900

1800

1700

1600

MEASUREMENT CONDITIONS

= 2.75V, T

= 25

= 100

Ω

||50

Ω

(100

Ω

RESISTIVE PULL-UP PARALLELED WITH 50

Ω

VNA IMPEDANCE), UNUSED OUTPUT TERMINATED IN 50

Ω

PCB PARASITIC SHUNT CAPACITANCE (IND TO GND) = 0.45pF

LOAD

THE INDUCTANCE LISTED IS THE PRECISE NOMINAL INDUCTANCE VALUE

REQUIRED FROM IND TO GND IN ORDER TO GUARANTEE THE VCO

CAN TUNE TO THE DESIRED FIXED FREQUENCY, OVER ALL OPERATING

CONDITIONS AND WORST-CASE COMPONENT

VALUES (

2% INDUCTOR AND IC PROCESS VARIATION).

1500

1400

1300

1200

1100

1000

900

EFFECTIVE INDUCTANCE

FROM IND TO GND

INDUCTOR VALUE

MOUNTED ON EV KIT

800

700

45 47

49 51 53 55

61 63 65 67 69

DESIRED VCO FIXED FREQUENCY (MHz)

Figure 1. MAX2605 Required Inductance vs. Desired VCO Fixed Frequency

_______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

MAX2606

REQUIRED INDUCTANCE vs. DESIRED VCO FIXED FREQUENCY

790

MEASUREMENT CONDITIONS

= 2.75V, T

= 25

= 100

Ω

||50

Ω

(100

Ω

RESISTIVE PULL-UP PARALLELED WITH 50

Ω

VNA IMPEDANCE), UNUSED OUTPUT TERMINATED IN 50

Ω

PCB PARASITIC SHUNT CAPACITANCE (IND TO GND) = 0.45pF

LOAD

740

690

THE INDUCTANCE LISTED IS THE PRECISE NOMINAL INDUCTANCE VALUE

REQUIRED FROM IND TO GND IN ORDER TO GUARANTEE THE VCO

CAN TUNE TO THE DESIRED FIXED FREQUENCY, OVER ALL OPERATING

CONDITIONS AND WORST-CASE COMPONENT

VALUES (

2% INDUCTOR AND IC PROCESS VARIATION).

640

590

540

490

440

390

340

290

240

EFFECTIVE INDUCTANCE

FROM IND TO GND

INDUCTOR VALUE

MOUNTED ON EV KIT

190

140

70 75 80

85 90

95 100

110 115 120 125

130 135 140

145 150

105

DESIRED VCO FIXED FREQUENCY (MHz)

Figure 2. MAX2606 Required Inductance vs. Desired VCO Fixed Frequency

_______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

MAX2607

REQUIRED INDUCTANCE vs. DESIRED VCO FIXED FREQUENCY

170

160

MEASUREMENT CONDITIONS

= 2.75V, T

= 25

= 100

Ω

||50

Ω

(100

Ω

RESISTIVE PULL-UP PARALLELED WITH 50

Ω

VNA IMPEDANCE), UNUSED OUTPUT TERMINATED IN 50

Ω

PCB PARASITIC SHUNT CAPACITANCE (IND TO GND) = 0.45pF

LOAD

150

140

THE INDUCTANCE LISTED IS THE PRECISE NOMINAL INDUCTANCE VALUE

REQUIRED FROM IND TO GND IN ORDER TO GUARANTEE THE VCO

CAN TUNE TO THE DESIRED FIXED FREQUENCY, OVER ALL OPERATING

CONDITIONS AND WORST-CASE COMPONENT

VALUES (

2% INDUCTOR AND IC PROCESS VARIATION).

130

120

110

100

EFFECTIVE INDUCTANCE

FROM IND TO GND

INDUCTOR VALUE

MOUNTED ON EV KIT

150 160 170

180 190

200 210

220 230 240

250 260 270 280

300

290

DESIRED VCO FIXED FREQUENCY (MHz)

Figure 3. MAX2607 Required Inductance vs. Desired VCO Fixed Frequency

_______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

MAX2608

REQUIRED INDUCTANCE vs. DESIRED VCO FIXED FREQUENCY

41.0

40.0

MEASUREMENT CONDITIONS

= 2.75V, T

= 25

38.0

37.0

36.0

35.0

34.0

= 100

Ω

||50

Ω

(100

Ω

RESISTIVE PULL-UP PARALLELED WITH 50

Ω

VNA IMPEDANCE), UNUSED OUTPUT TERMINATED IN 50

Ω

PCB PARASITIC SHUNT CAPACITANCE (IND TO GND) = 0.45pF

LOAD

THE INDUCTANCE LISTED IS THE PRECISE NOMINAL INDUCTANCE VALUE

REQUIRED FROM IND TO GND IN ORDER TO GUARANTEE THE VCO

CAN TUNE TO THE DESIRED FIXED FREQUENCY, OVER ALL OPERATING

CONDITIONS AND WORST-CASE COMPONENT

VALUES (

2% INDUCTOR AND IC PROCESS VARIATION).

33.0

32.0

31.0

30.0

29.0

28.0

27.0

26.0

25.0

24.0

23.0

22.0

EFFECTIVE INDUCTANCE

FROM IND TO GND

21.0

20.0

19.0

18.0

17.0

16.0

15.0

14.0

13.0

INDUCTOR VALUE

MOUNTED ON EV KIT

12.0

11.0

10.0

9.0

300 310 320 330 340 350 360 370 380 390

400 410 420 420 430 440 450 460 470 480 490 500

Figure 4. MAX2608 Required Inductance vs. Desired VCO Fixed Frequency

10 ______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

MAX2609

REQUIRED INDUCTANCE vs. DESIRED VCO FIXED FREQUENCY

14.0

13.5

MEASUREMENT CONDITIONS

= 2.75V, T

= 25

= 100

Ω

||50

Ω

(100

Ω

RESISTIVE PULL-UP PARALLELED WITH 50

Ω

VNA IMPEDANCE), UNUSED OUTPUT TERMINATED IN 50

Ω

PCB PARASITIC SHUNT CAPACITANCE (IND TO GND) = 0.45pF

LOAD

13.0

12.5

THE INDUCTANCE LISTED IS THE PRECISE NOMINAL INDUCTANCE VALUE

REQUIRED FROM IND TO GND IN ORDER TO GUARANTEE THE VCO

CAN TUNE TO THE DESIRED FIXED FREQUENCY, OVER ALL OPERATING

CONDITIONS AND WORST-CASE COMPONENT

12.0

11.5

11.0

VALUES (

2% INDUCTOR AND IC PROCESS VARIATION).

10.5

10.0

9.5

EFFECTIVE INDUCTANCE

FROM IND TO GND

9.0

8.5

8.0

7.5

7.0

6.5

INDUCTOR VALUE

MOUNTED ON EV KIT

6.0

5.5

5.0

4.5

4.0

3.5

500 510 520

530 540

550 560

570 580 590

600 610 620 630

650

640

DESIRED VCO FIXED FREQUENCY (MHz)

Figure 5. MAX2609 Required Inductance vs. Desired VCO Fixed Frequency

______________________________________________________________________________________ 11

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

the cathode of the varactor. This is accomplished

through the use of a simple bypass capacitor connect-

ed from TUNE to ground. The value of this capacitor

should be greater than or equal to the values listed in

Table 2.

from OUT- and OUT+ (in place of resistors) to V

provide DC bias for the output stage. The series capac-

itors are connected from OUT- and OUT+ to the load.

The values for L

(Z and

Z ) and C

MATCH 1

MATCH

and C ) are chosen according to the operating fre-

quency and load impedance. As the output stage is

essentially a high-speed current switch, traditional lin-

ear impedance using techniques with [S] parameters

do not apply. To achieve a reactive power match, start

with the component values provided in the EV kit, and

adꢀust values experimentally.

This capacitor provides an AC “short” to ground for the

internal node of the varactor. It is acceptable to select

the next-largest standard-value capacitor. Use a

capacitor with a low-loss dielectric such as NPO; X7R-

based capacitors are

not

suitable. Omitting this capac-

itor would affect the tuning characteristics of the

MAX2605–MAX2609. Proper operation of the VCOs

requires the use of this bypass capacitor.

In general, the differential output may be applied in any

manner, as would conventional differential outputs. The

only constraints are the need for a pull-up element to

The MAX2605–MAX2609 VCO is designed to tune over

the full tuning range with a voltage range of 0.4V to

2.4V applied to TUNE. This voltage typically originates

from the output of the phase-locked (PLL) loop filter.

and a voltage swing limit at the output pins OUT-

and OUT+.

Layout Considerations

In general, a properly designed PC board is essential

to any RF/microwave circuit or system. Always use con-

trolled impedance lines (microstrip, coplanar wave-

guide, etc.) on high-frequency signals. Always place

Output Interface

The MAX2605–MAX2609 VCO includes a differential

output amplifier after the oscillator core. The amplifier

stage provides valuable isolation and offers a flexible

interface to the IF stages, such as a mixer and PLL

prescaler. The output can be taken single ended or dif-

ferentially; however, the maximum output power and

lowest harmonic output are achieved in the differential

output mode.

decoupling capacitors as close to the V

pin as pos-

sible. For low phase noise and spurious content, use an

appropriate size decoupling capacitor. For long V

lines, it may be necessary to add additional decoupling

capacitors located further from the device. Always pro-

vide a low-inductance path to ground. Keep the GND

vias as close to the device as possible. In addition, the

VCO should be placed as far away from the noisy sec-

tion of a larger system, such as a switching regulator or

digital circuits. Use star topology to separate the

ground returns.

Both outputs (OUT- and OUT+) are open-collector

types and require a pull-up element to V

; this can be

either resistive or inductive. A resistor pull-up is the

most straightforward method of interfacing to the out-

put, and works well in applications that operate at lower

frequencies or only require a modest voltage swing.

The resonator tank circuit (L ) is critical in determining

In Figure 6, Z1 and Z2 are 1k

Ω

pull-up resistors that are

connected from OUT+ and OUT- to V

, respectively.

the VCO’s performance. For best performance, use

high-Q components and choose values carefully. To

minimize the effects of parasitic elements, which

These resistors provide DC bias for the output amplifier

and are the maximum value permitted with compliance

to the output voltage swing limits. In addition, the 1k

Ω

resistors maximize the swing at the load. DC-blocking

capacitors are connected from OUT- and OUT+ to the

load. If the load driven is primarily resistive and the

VCO operating frequency is below the -3dB bandwidth

of the output network, then the peak-to-peak differential

signal amplitude is approximately:

degrade circuit performance, place L

and C

BYP

to their respective pins. Specifically, place C

ly across pins 2 (GND) and 3 (TUNE).

direct-

BYP

For the higher frequency versions, consider the extra

parasitic inductance and capacitance when determin-

ing the oscillation frequency. Be sure to account for the

following: PC board pad capacitance at IND, PC board

pad capacitance at the ꢀunction of two series inductors,

series inductance of any PC board traces, and the

inductance in the ground return path from the ground-

ed side of the inductor and IC’s GND pin. For best

results, connect the “ground” side to the tuning induc-

tor as close to pin 2 as possible. In addition, remove





Ω ×

LOAD

diff

1mA





OUTp

−

(

)





Ω +





LOAD

To optimize the output voltage swing or the output

power, use a reactive power match. The matching net-

work is a simple shunt-inductor series-capacitor circuit,

as shown in Figure 6. The inductors are connected

the ground plane around and under L

and C

minimize the effects of parasitic capacitance.

BYP

12 ______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

OUT+

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

LOAD

BYP

TUNE

OUT-

FROM PLL

LOOP

FILTER OUTPUT

Figure 6. Typical Operating Circuit

Chip Information

TRANSISTOR COUNT: 158

______________________________________________________________________________________ 13

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

= X

/ 2

π ƒ

L NOMINAL

IND

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

PAR1

PAR2

Figure 8. Inductive Reactance at Pin 1 (IND)

Figure 7. Simple Model of External Inductance

MAX2605

MAX2606

MAX2607

MAX2608

MAX2609

Figure 9. Output Matching Network

14 ______________________________________________________________________________________

45MHz to 650MHz, Integrated IF

VCOs with Differential Output

Package Information

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

408-737-760

____________________

Maxim Integrated Products

Printed USA

is a registered trademark of Maxim Integrated Products.

Analog-Devices-Inc–Maxim-Integrated-MAX2607EUT

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