LTC6401-26_技术文档

LTC6401-26

1.6GHz Low Noise,

Low Distortion Differential

ADC Driver for DC-140MHz

FEATURES

DESCRIPTION

The LTC^®6401-26 is a high-speed differential ampliﬁer

targeted at processing signals from DC to 140MHz. The

part has been speciﬁcally designed to drive 12-, 14- and

16-bitADCswithlownoiseandlowdistortion,butcanalso

be used as a general-purpose broadband gain block.

■

1.6GHz –3dB Bandwidth

■

Fixed Gain of 20V/V (26dB)

■

–85dBc IMD3 at 70MHz (Equivalent OIP3 = 46.5dBm)

■

–72dBc IMD3 at 140MHz (Equivalent OIP3 = 40dBm)

■

1nV/√Hz Internal Op Amp Noise

■

1.5nV/√Hz Total Input Referred Noise

The LTC6401-26 is easy to use, with minimal support

circuitry required. The output common mode voltage is

set using an external pin, independent of the inputs, which

eliminates the need of transformers or AC-coupling ca-

pacitors in many applications. The gain is internally ﬁxed

at 26dB (20V/V).

■

6.8dB Noise Figure

■

Differential Inputs and Outputs

■

50Ω Input Impedance

■

2.85V to 3.5V Supply Voltage

■

45mA Supply Current (135mW)

■

1V to 1.6V Output Common Mode, Adjustable

■

The LTC6401-26 saves space and power compared to

alternative solutions using IF gain blocks and transform-

ers. The LTC6401-26 is packaged in a compact 16-lead

3mm × 3mm QFN package and operates over the –40°C

to 85°C temperature range.

DC- or AC-Coupled Operation

Max Differential Output Swing 4.7V

■

P-P

■

Small 16-Lead 3mm × 3mm × 0.75mm QFN Package

APPLICATIONS

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

■

Differential ADC Driver

■

Differential Driver/Receiver

■

Single Ended to Differential Conversion

IF Sampling Receivers

SAW Filter Interfacing

■

TYPICAL APPLICATION

Equivalent OIP3 vs Frequency

Single-Ended to Differential ADC Driver at 140MHz IF

60

3.3V

DIFFERENTIAL INPUT

(NOTE 7)

50

0.1μF

1000pF

33pF

40

30

+

V

0.1μF

15Ω

10Ω

V

DD

+

–

+OUT

AIN

V

+IN

IN

L1

24nH

150Ω

20

10

0

LTCL6T4C0614-2061-26

33pF

LTC2208

–IN

–OUT

AIN

V

CM

V

OCM

V

NO R

L

OCM

37.4Ω

–

COILCRAFT

0603CS

R

L

= 200Ω

LTC2208

130Msps

16-BIT ADC

V

0

50

100

150

200

1.25V

640126 TA01a

FREQUENCY (MHz)

100Ω

640126 TA01b

0.1μF

640126f

1

LTC6401-26

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Note 1)

TOP VIEW

+

–

Supply Voltage (V – V )..........................................3.6V

Input Current (Note 2).......................................... 10mA

Operating Temperature Range

16 15 14 13

+

–

V

1

2

3

4

12 V

(Note 3) ............................................... –40°C to 85°C

Speciﬁed Temperature Range

(Note 4) ............................................... –40°C to 85°C

Storage Temperature Range................... –65°C to 150°C

Maximum Junction Temperature .......................... 150°C

V

11 ENABLE

+

OCM

+

17

V

10

9

–

V

5

6

7

8

UD PACKAGE

16-LEAD (3mm × 3mm) PLASTIC QFN

= 150°C, θ = 68°C/W, θ = 4.2°C/W

T

JMAX

JA

JC

–

EXPOSED PAD (PIN 17) IS V , MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

LTC6401CUD-26#PBF

LTC6401IUD-26#PBF

TAPE AND REEL

PART MARKING*

PACKAGE DESCRIPTION

SPECIFIED TEMPERATURE RANGE

LTC6401CUD-26#TRPBF LCDG

LTC6401IUD-26#TRPBF LCDG

16-Lead (3mm × 3mm) Plastic QFN

0°C to 70°C

–40°C to 85°C

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges. *The temperature grade is identiﬁed by a label on the shipping container.

Consult LTC Marketing for information on non-standard lead based ﬁnish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁcations, go to: http://www.linear.com/tapeandreel/

LTC6400 AND LTC6401 SELECTOR GUIDE ^{Please check each datasheet for complete details.}

PART NUMBER

GAIN

(dB)

GAIN

(V/V)

Z

IN

(DIFFERENTIAL)

I

CC

(mA)

(Ω)

LTC6401-8

LTC6401-20

LTC6401-26

LTC6400-20

LTC6400-26

8

2.5

10

20

10

20

400

200

50

45

20

26

20

26

50

45

200

50

90

85

In addition to the LTC6401 family of ampliﬁers, a lower distortion LTC6400 family is available. The LTC6400 is pin compatible to the LTC6401, and has the

same low noise performance. The low distortion of the LTC6400 comes at the expense of higher power consumption. Please refer to the separate LTC6400

data sheets for complete details. Other gain versions from 8dB to 14dB will follow.

640126f

2

LTC6401-26

DC ELECTRICAL CHARACTERISTICS ^The● denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C. V⁺= 3V, V^–= 0V, +IN = –IN = V_OCM= 1.25V, ENABLE = 0V, No R_Lunless

otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Input/Output Characteristic (+IN, –IN, +OUT, –OUT, +OUTF, –OUTF)

●

G

Gain

V

=

50mV Differential

25

26

0.003

0.09

2.43

4.7

27

dB

dB/°C

V

DIFF

IN

TC

Gain Temperature Drift

Output Swing Low

Output Swing High

Maximum Differential Output Swing

Output Current Drive

GAIN

IN

V

Each Output, V

=

200mV Differential

0.15

SWINGMIN

SWINGMAX

OUTDIFFMAX

OUT

IN

2.3

4.3

10

V

1dB Compressed

Each Output, V

V

P-P

I

=

200mV,

mA

IN

V

OUT

> 2V

P-P

●

V

Input Offset Voltage

Differential

–2.5

2.5

1

mV

μV/°C

V

OS

TCV

Input Offset Voltage Drift

1

OS

VRMIN

VRMAX

I

Input Common Mode Voltage Range, MIN

Input Common Mode Voltage Range, MAX

Input Resistance (+IN, –IN)

1.6

V

●

Ω

R

Differential

42.5

50

1

57.5

INDIFF

C

Input Capacitance (+IN, –IN)

Differential, Includes Parasitic

Differential

pF

●

Ω

R

Output Resistance (+OUT, –OUT)

Filtered Output Resistance (+OUTF, –OUTF)

18

85

25

100

2.7

75

32

OUTDIFF

OUTFDIFF

Ω

Differential

115

C

Filtered Output Capacitance (+OUTF, –OUTF) Differential, Includes Parasitic

pF

●

CMRR

Common Mode Rejection Ratio

Input Common Mode Voltage

1.1V to1.4V

50

dB

Output Common Mode Control

G

Common Mode Gain

V

= 1V to 1.6V

1

V/V

CM

OCM

V

Output Common Mode Range, MIN

1

V

OCMMIN

●

1.1

Output Common Mode Range, MAX

1.6

1.5

V

OCMMAX

●

Common Mode Offset Voltage

V

= 1.1V to 1.5V

–15

15

mV

μV/°C

μA

OSCM

TCV

Common Mode Offset Voltage Drift

3

5

OSCM

IV

V

Input Current

OCM

ENABLE Pin

●

V

ENABLE Input Low Voltage

ENABLE Input High Voltage

ENABLE Input Low Current

ENABLE Input High Current

0.8

V

IL

2.4

IH

I

IL

I

IH

ENABLE = 0.8V

ENABLE = 2.4V

0.5

3

μA

1.4

Power Supply

●

V

Operating Supply Range

Supply Current

2.85

35

3

3.5

60

V

S

I

S

ENABLE = 0V, Both Inputs and

Outputs Floating

45

mA

●

I

Shutdown Supply Current

ENABLE = 3V, Both Inputs and

Outputs Floating

0.8

3

mA

dB

SHDN

PSRR

Power Supply Rejection Ratio (Differential

Outputs)

2.85V to 3.5V

60

95.5

640126f

3

LTC6401-26

AC ELECTRICAL CHARACTERISTICS Speciﬁcations are at T_A= 25°C. V⁺= 3V, V^–= 0V, V_OCM= 1.25V,

ENABLE = 0V, No R_Lunless otherwise noted.

SYMBOL

–3dBBW

0.5dBBW

0.1dBBW

1/f

PARAMETER

CONDITIONS

MIN

TYP

1.6

0.5

0.22

16

MAX

UNITS

GHz

kHz

V/μs

ns

–3dB Bandwidth

200mV

(Note 6)

1.2

P-P,OUT

Bandwidth for 0.5dB Flatness

Bandwidth for 0.1dB Flatness

1/f Noise Corner

SR

Slew Rate

Differential V

= 2V Step (Note 6)

3300

3

OUT

t

1% Settling Time

Overdrive Recovery Time

Turn-On Time

V

OUT

V

OUT

= 2V (Note 6)

P-P

S1%

OVDR

ON

= 1.9V (Note 6)

19

ns

P-P

+OUT, –OUT Within 10% of Final Values

Falls to 10% of Nominal

93

ns

Turn-Off Time

I

140

14.7

ns

OFF

CC

–3dBBW

V

Pin Small Signal –3dB BW

0.1V at V , Measured Single-Ended

OCM

MHz

VOCM

OCM

P-P

at Output (Note 6)

10MHz Input Signal

HD2,10M/HD3,10M Second/Third Order Harmonic Distortion

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

= 2V , R = 200Ω

–95/–81

–93/–96

–80

dBc

dBm

P-P

L

= 2V , No R

P-P

L

IMD3,10M

OIP3,10M

Third-Order Intermodulation

(f1 = 9.5MHz f2 = 10.5MHz)

= 2V Composite, R = 200Ω

P-P L

= 2V Composite, No R

–97

P-P

L

Equivalent Third-Order Output Intercept

Point (f1 = 9.5MHz f2 = 10.5MHz)

= 2V Composite, No R (Note 7)

52.5

P-P

L

P

1dB Compression Point

R = 375Ω (Notes 5, 7)

17.3

6.8

1.5

30

dBm

dB

1dB,10M

L

NF

Noise Figure

R = 375Ω (Note 5)

L

10M

e

Input Referred Voltage Noise Density

Output Referred Voltage Noise Density

Includes Resistors (Short Inputs)

nV/√Hz

IN,10M

ON,10M

70MHz Input Signal

HD2,70M/HD3,70M Second/Third Order Harmonic Distortion

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

= 2V , R = 200Ω

–83/–66

–86/–81

–74

dBc

dBm

P-P

L

= 2V , No R

P-P

L

IMD3,70M

OIP3,70M

Third-Order Intermodulation

(f1 = 69.5MHz f2 = 70.5MHz)

= 2V Composite, R = 200Ω

P-P L

= 2V Composite, No R

–85

P-P

L

Equivalent Third-Order Output Intercept

Point (f1 = 69.5MHz f2 = 70.5MHz)

= 2V Composite, No R (Note 7)

46.5

P-P

L

P

1dB Compression Point

R = 375Ω (Notes 5, 7)

17.2

6.7

dBm

dB

1dB,70M

L

NF

Noise Figure

R = 375Ω (Note 5)

L

70M

e

Input Referred Voltage Noise Density

Output Referred Voltage Noise Density

Includes Resistors (Short Inputs)

1.44

28.8

nV/√Hz

IN,70M

ON,70M

640126f

4

LTC6401-26

AC ELECTRICAL CHARACTERISTICS ^{Speciﬁcations are at T}_A^{= 25°C. V}⁺^{= 3V, V}^–^{= 0V, V}_OCM= 1.25V,

ENABLE = 0V, No R_Lunless otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

140MHz Input Signal

HD2,140M/

HD3,140M

Second/Third Order Harmonic Distortion

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

= 2V , R = 200Ω

–81/–54

–85/–69

–64

dBc

dBm

P-P

L

= 2V , No R

P-P

L

IMD3,140M

Third-Order Intermodulation

(f1 = 139.5MHz f2 = 140.5MHz)

= 2V Composite, R = 200Ω

P-P L

= 2V Composite, No R

–72

P-P

L

OIP3,140M

Equivalent Third-Order Output Intercept

Point(f1 = 139.5MHz f2 = 140.5MHz)

= 2V Composite, No R (Note 7)

40

P-P

L

P

1dB Compression Point

R = 375Ω (Notes 5, 7)

17.4

6.5

dBm

dB

1dB,140M

L

NF

Noise Figure

R = 375Ω (Note 5)

L

140M

N,140M

ON,140M

e

Input Referred Voltage Noise Density

Output Referred Voltage Noise Density

Includes Resistors (Short Inputs)

1.43

28.6

–70

nV/√Hz

dBc

IMD

Third-Order Intermodulation

(f1 = 130MHz f2 = 150MHz)

Measure at 170MHz

V

= 2V Composite, R = 375Ω

–62

3,130M/150M

OUT

P-P

L

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2: Input pins (+IN, –IN) are protected by steering diodes to either

supply. If the inputs go beyond either supply rail, the input current should

be limited to less than 10mA.

temperatures. The LTC6401I is guaranteed to meet speciﬁed performance

from –40°C to 85°C.

Note 5: Input and output baluns used. See Test Circuit A.

Note 6: Measured using Test Circuit B. R = 87.5Ω per output.

L

Note 7: Since the LTC6401-26 is a feedback ampliﬁer with low output

impedance, a resistive load is not required when driving an AD converter.

Therefore, typical output power is very small. In order to compare the

LTC6401-26 with ampliﬁers that require 50Ω output load, the output

Note 3: The LTC6401C and LTC6401I are guaranteed functional over the

operating temperature range of –40°C to 85°C

voltage swing driving a given R is converted to OIP and P as if it were

L

3

1dB

Note 4: The LTC6401C is guaranteed to meet speciﬁed performance from

0°C to 70°C. It is designed, characterized and expected to meet speciﬁed

performance from –40°C to 85°C but is not tested or QA sampled at these

driving a 50Ω load. Using this modiﬁed convention, 2V is by deﬁnition

P-P

equal to 10dBm, regardless of actual R .

L

640126f

5

LTC6401-26

TYPICAL PERFORMANCE CHARACTERISTICS

Frequency Response

Gain 0.1dB Flatness

30

25

20

15

10

5

1.0

0.8

TEST CIRCUIT B

0.6

0.4

0.2

0

–0.2

–0.4

–0.6

–0.8

–1.0

TEST CIRCUIT B

0

10

100

FREQUENCY (MHz)

1000

3000

10

100

1000

3000

FREQUENCY (MHz)

640126 G02

640126 G01

Input and Output Reﬂection and

Reverse Isoloation vs Frequency

S21 Phase and Group Delay vs

Frequency

0

–50

0.8

0.6

0.4

0.2

0

–10

–20

–30

–40

–50

–60

–70

TEST CIRCUIT B

S11

S22

S12

GROUP DELAY

–100

–150

–200

PHASE

TEST CIRCUIT B

0

200

400

600

800

1000

10

100

1000

3000

FREQUENCY (MHz)

640126 G04

640126 G03

Input and Output Impedance vs

Frequency

PSRR and CMRR vs Frequency

180

150

120

90

60

50

40

30

20

10

0

120

Z

MAG

IN

OUT

MAG

PHASE

IN

OUT

100

80

60

40

20

0

PSRR

CMRR

PHASE

60

30

0

10

100

FREQUENCY (MHz)

1000

1

10

100

1000

FREQUENCY (MHz)

640126 G05

640126 G06

640126f

6

LTC6401-26

TYPICAL PERFORMANCE CHARACTERISTICS

Noise Figure and Input Referred

Noise Voltage vs Frequency

Small Signal Transient Response

1.35

1.30

1.25

1.20

1.15

9

8

7

6

5

2.0

1.5

1.0

0.5

0

R

= 87.5Ω PER OUTPUT

L

TEST CIRCUIT B

+OUT

EN

–OUT

NOISE FIGURE

0

2

4

6

8

10

1000

10

100

TIME (ns)

FREQUENCY (MHz)

640126 G07

640126 G08

Overdriven Transient Response

Large Signal Transient Response

2.5

2.0

1.5

1.0

0.5

0

2.5

R

L

= 87.5Ω PER OUTPUT

R

= 87.5Ω PER OUTPUT

L

TEST CIRCUIT B

–OUT

2.0

1.5

1.0

0.5

0

+OUT

–OUT

+OUT

TEST CIRCUIT B

50

0

100

150

200

250

0

4

8

12

16

20

TIME (ns)

640126 G10

640126 G09

1% Settling Time for

2V Output Step

Harmonic Distortion vs Frequency

–40

–50

5

DIFFERENTIAL INPUT

V

OUT

= 2V

4

3

P-P

–60

2

1

–70

0

–80

–1

–2

–3

–4

–5

–90

HD2 NO R

L

HD2 R = 200Ω

L

–100

–110

HD3 NO R

R

= 87.5Ω PER OUTPUT

L

HD3 R = 200Ω

TEST CIRCUIT B

L

200

0

1

2

3

4

5

0

50

100

150

TIME (ns)

FREQUENCY (MHz)

640126 G11

640126 G12

640126f

7

LTC6401-26

TYPICAL PERFORMANCE CHARACTERISTICS

Third Order Intermodulation

Distortion vs Frequency

Third Order Intermodulation

Distortion vs Frequency

Harmonic Distortion vs Frequency

–40

–50

–40

–50

–40

–50

DIFFERENTIAL INPUT

SINGLE-ENDED INPUT

V

= 2V COMPOSITE

V

= 2V COMPOSITE

V

= 2V

OUT

P-P

OUT

P-P

OUT

P-P

–60

–70

–80

–90

HD2 NO R

L

HD2 R = 200Ω

L

–100

–110

–100

–110

–100

–110

NO R

L

NO R

L

HD3 NO R

L

R

= 200Ω

R

= 200Ω

HD3 R = 200Ω

L

200

0

50

100

150

200

0

50

100

150

0

150

50

100

FREQUENCY (MHz)

640126 G13

640126 G14

640126 G15

Output 1dB Compression Point vs

Frequency

Equivalent Output Third Order

Intercept Point vs Frequency

60

50

19.0

18.5

DIFFERENTIAL INPUT

(NOTE 7)

DIFFERENTIAL INPUT

R

= 375Ω

L

TEST CIRCUIT A

(NOTE 7)

40

30

18.0

17.5

20

10

0

17.0

16.5

16.0

NO R

L

R

= 200Ω

0

50

100

150

200

0

50

100

150

200

FREQUENCY (MHz)

640126 G17

640126 G16

Turn-On Time

Turn-Off Time

3.5

3.0

2.5

2.0

70

60

50

40

3.5

3.0

2.5

2.0

70

R

L

= 87.5Ω PER OUTPUT

R

L

= 87.5Ω PER OUTPUT

60

50

40

ENABLE

I

CC

–OUT

+OUT

1.5

1.0

30

20

1.5

1.0

30

20

+OUT

0.5

0

10

0

0.5

0

10

0

I

CC

ENABLE

–0.5

–10

–0.5

–10

0

100

300

0

100

300

–100

400

500

–100

400

500

200

TIME (ns)

640126 G19

640126 G18

640126f

8

LTC6401-26

PIN FUNCTIONS

V (Pins 1, 3, 10): Positive Power Supply (Normally tied

to 3V or 3.3V). All three pins must be tied to the same

voltage. Bypass each pin with 1000pF and 0.1μF capaci-

tors as close to the pins as possible.

+

–OUTF, +OUTF (Pins 6, 7): Filtered Outputs. These pins

have 50Ω series resistors and a 2.7pF shunt capacitor.

ENABLE (Pin 11): This pin is a logic input referenced to

V . If low, the part is enabled. If high, the part is disabled

EE

V

(Pin 2): This pin sets the output common mode

and draws very low standby current while the internal op

OCM

voltage. An 0.1μF external bypass capacitor is recom-

amp has high output impedance.

mended.

+IN (Pins 13, 14): Positive Input. Pins 13 and 14 are

internally shorted together.

–

V (Pins 4, 9, 12, 17): Negative Power Supply. All four

pins must be connected to same voltage/ground.

–IN (Pins 15, 16): Negative Input. Pins 15 and 16 are

internally shorted together.

–OUT, +OUT (Pins 5, 8): Unﬁltered Outputs. These pins

have series 12.5Ω resistors R

.

–

OUT

Exposed Pad (Pin 17): V . The Exposed Pad must be

connected to same voltage/ground as pins 4, 9, 12.

BLOCK DIAGRAM

–

+

–

V

ENABLE

V

12

11

10

9

BIAS CONTROL

R

F

500Ω

R

OUT

12.5Ω

G

+IN

13

+OUT

25Ω

8

R

FILT

+OUTF

50Ω

+IN

–IN

IN+

IN–

OUT–

7

14

15

C

FILT

R

FILT

2.7pF

–OUTF

–OUT

50Ω

6

5

OUT+

R

G

25Ω

R

OUT

12.5Ω

F

–IN

16

500Ω

2k

COMMON

MODE CONTROL

5.3pF

640126 BD

1

2

3

4

+

–

V

OCM

640126f

9

LTC6401-26

APPLICATIONS INFORMATION

Circuit Operation

them if the source is differential (Figure 1). Another ap-

proach is to employ a wideband transformer if the source

is single ended (Figure 2). Both methods provide a wide-

band match. Alternatively, one could apply a narrowband

impedance match at the inputs of the LTC6401-26 for

frequency selection and/or noise reduction.

The LTC6401-26 is a low noise and low distortion fully

differential op amp/ADC driver with:

• Operation from DC to 1.6GHz –3dB bandwidth

• Fixed gain of 20V/V (26dB)

ReferringtoFigure3,LTC6401-26canbeeasilyconﬁgured

for single-ended input and differential output without a

balun. The signal is fed to one of the inputs through a

matchingnetworkwhiletheotherinputisconnectedtothe

samematchingnetworkandasourceresistor.Becausethe

return ratios of the two feedback paths are equal, the two

outputshavethesamegainandthussymmetricalswing.In

general,thesingle-endedinputimpedanceandtermination

• Differential input impedance 50Ω

• Differential output impedance 25Ω

• Differential impedance of output ﬁlter 100Ω

TheLTC6401-26iscomposedofafullydifferentialampliﬁer

with on chip feedback and output common mode voltage

control circuitry. Differential gain and input impedance

are set by 25Ω/500Ω resistors in the feedback network.

Smalloutputresistorsof12.5Ωimprovethecircuitstability

over various load conditions. They also provide a possible

external ﬁltering option, which is often desirable when the

load is an ADC.

resistor R are determined by the combination of R , R

T

S

G

and R . For example, when R is 50Ω, it is found that the

F

S

single-ended input impedance is 75Ω and R is 150Ω in

T

order to match to a 50Ω source impedance.

LTC6401-26

500Ω

25Ω

12.5Ω

50Ω

Filter resistors of 50Ω are available for additional ﬁltering.

Lowpass/bandpassﬁltersareeasilyimplementedwithjust

a couple of external components. Moreover, they offer

single-ended 50Ω matching in wideband applications and

no external resistor is needed.

13 +IN

+OUT

8

IN+

IN–

OUT–

+OUTF

7

V

IN

14 +IN

15 –IN

+

–

50Ω

2.7pF

–OUTF

6

5

OUT+

500Ω

The LTC6401-26 is very ﬂexible in terms of I/O coupling.

It can be AC- or DC-coupled at the inputs, the outputs or

both. Due to the internal connection between input and

output, users are advised to keep input common mode

voltage between 1V and 1.6V for proper operation. If the

inputs are AC-coupled, the input common mode voltage

25Ω

12.5Ω

16 –IN

–OUT

640126 F01

Figure 1. Input Termination for Differential 50Ω Input Impedance

is automatically biased close to V

and thus no external

OCM

LTC6401-26

500Ω

50Ω

25Ω

12.5Ω

50Ω

circuitry is needed for bias. The LTC6401-26 provides an

output common mode voltage set by V , which allows

13 +IN

+OUT

8

OCM

driving ADC directly without external components such as

transformer or AC coupling capacitors. The input signal

can be either single-ended or differential with only minor

difference in distortion performance.

IN+

IN–

OUT–

1:1

+OUTF

7

V

IN

14 +IN

15 –IN

+

–

50Ω

2.7pF

–OUTF

6

5

OUT+

500Ω

25Ω

12.5Ω

16 –IN

–OUT

640126 F02

Input Impedance and Matching

M/A-COM

MABA-007159-000000

ThedifferentialinputimpedanceoftheLTC6401-26is50Ω.

The interface between the input of LTC6401-26 and 50Ω

source is straightforward. One way is to directly connect

Figure 2. Input Termination for Differential 50Ω Input Impedance

Using a Balun

640126f

10

LTC6401-26

APPLICATIONS INFORMATION

R

S

LTC6401-26

The internal low pass ﬁlter outputs at +OUTF/–OUTF have

a –3dB bandwidth of 590MHz. External capacitors can

reduce the low pass ﬁlter bandwidth as shown in Figure

5. A bandpass ﬁlter is easily implemented with only a

few components as shown in Figure 6. Three 39pF ca-

pacitors and 16nH inductor create a bandpass ﬁlter with

165MHz center frequency, –3dB frequencies at 138MHz

and 200MHz.

0.1μF

500Ω

50Ω

25Ω

12.5Ω

13 +IN

+OUT

8

V

IN

+

50Ω

–

R

T

IN+

IN–

OUT–

150Ω

+OUTF

7

14 +IN

15 –IN

0.1μF

50Ω

2.7pF

–OUTF

6

5

OUT+

500Ω

0.1μF

25Ω

12.5Ω

16 –IN

–OUT

640126 F03

37.4Ω

Output Common Mode Adjustment

Figure 3. Input Termination for Single-Ended 50Ω Input

The LTC6401-26’s output common mode voltage is set

Impedance

by the V

pin, which is a high impedance input. The

OCM

The LTC6401-26 is unconditionally stable, i.e. differential

stability factor Kf>1 and stability measure B1>0. However,

the overall differential gain is affected by both source

impedance and load impedance as shown in Figure 4:

output common mode voltage is capable of tracking V

OCM

control is

in a range from 1V to 1.6V. Bandwidth of V

OCM

typically 15MHz, which is dominated by a low pass ﬁlter

connected to the V pin and is aimed to reduce com-

OCM

mon mode noise generation at the outputs. The internal

common mode feedback loop has a –3dB bandwidth of

400MHz, allowing fast rejection of any common mode

V_OUT

R_L

R_S+50 25+R_L

1000

A_V=

=

•

V

IN

output voltage disturbance. The V

pin should be tied

OCM

The noise performance of the LTC6401-26 also depends

upon the source impedance and termination. A trade-off

between gain and noise is obvious when constant noise

ﬁgure circle and constant gain circle are plotted within

the same input Smith Chart, based on which users can

choose the optimal source impedance for a given gain

and noise requirement.

to a DC bias voltage with a 0.1μF bypass capacitor. When

interfacing with 3V A/D converters such as the LTC22xx

families, the V

of the ADC.

pin can be connected to the V pin

OCM

CM

Driving A/D Converters

TheLTC6401-26hasbeenspeciﬁcallydesignedtointerface

directlywithhighspeedA/Dconverters.Figure7showsthe

LTC6401-26withsingle-endedinputdrivingtheLTC2208,

whichisa16-bit,130MspsADC.Twoexternal5Ωresistors

help eliminate potential resonance associated with bond

Output Impedance Match and Filter

TheLTC6401-26candriveanADCdirectlywithoutexternal

output impedance matching. Alternatively, the differential

output impedance of 25Ω can be made larger, e.g. 50Ω,

by series resistors or LC network.

wires of either the ADC input or the driver output. V

OCM

LTC6401-26

500Ω

1/2 R

25Ω

12.5Ω

50Ω

1/2 R

25Ω

12.5Ω

50Ω

S

L

13 +IN

+OUT

8

13 +IN

+OUT

8

8pF

IN+

IN–

OUT–

IN+

IN–

OUT–

+OUTF

7

+OUTF

7

V

IN

FILTERED OUTPUT

(87.5MHz)

14 +IN

15 –IN

14 +IN

15 –IN

V

OUT

+

12pF

8pF

–

50Ω

2.7pF

–OUTF

6

5

–OUTF

6

5

OUT+

500Ω

OUT+

500Ω

1/2 R

25Ω

12.5Ω

1/2 R

25Ω

12.5Ω

S

L

16 –IN

–OUT

16 –IN

–OUT

640126 F04

640126 F05

Figure 4. Calculate Differential Gain

Figure 5. LTC6401-26 Internal Filter Topology Modiﬁed for Low

Filter Bandwidth (Three External Capacitors)

640126f

11

LTC6401-26

APPLICATIONS INFORMATION

–40

–50

SINGLE-ENDED INPUT

= 122.8Msps

F

S

DRIVER V

= 2V COMPOSITE

OUT

P-P

–60

39pF

LTC6401-26

12.5Ω

–70

500Ω

25Ω

10Ω

4.99Ω

13 +IN

+OUT

8

–80

50Ω

IN+

IN–

OUT–

+OUTF

7

–90

14 +IN

15 –IN

16nH

39pF

LTC2208

1.7pF

50Ω

–100

–110

OUT+

500Ω

–OUTF

6

5

25Ω

12.5Ω

10Ω

4.99Ω

200

0

50

100

150

16 –IN

–OUT

640126 F06

FREQUENCY (MHz)

39pF

640126 F08

Figure 6. LTC6401-26 with 165MHz Output Bandpass Filter

Figure 8. IMD₃for the Combination of LTC6401-26 and LTC2208

of the LTC6401-26 is connected to V of the LTC2208

Test Circuit B uses a 4-port network analyzer to measure

S-parameters and gain/phase response. This removes the

effects of the wideband baluns and associated circuitry,

for a true picture of the >1GHz S-parameters and AC

characteristics.

CM

at 1.25V. Alternatively, a single-ended input signal can be

converted to a differential signal via a balun and fed to the

input of the LTC6401-26. Figure 8 summarizes the IMD3

performance of the whole system as shown in Figure 7.

Test Circuits

Due to the fully-differential design of the LTC6401 and

its usefulness in applications with differing characteristic

speciﬁcations, two test circuits are used to generate the

information in this datasheet. Test Circuit A is DC987B,

a two-port demonstration circuit for the LTC6401 family.

The silkscreen is shown in Figure 9. This circuit includes

input and output transformers (baluns) for single-ended-

to-differential conversion and impedance transformation,

allowing direct hook-up to a 2-port network analyzer.

There are also series resistors at the output to present the

LTC6401witha375Ωdifferentialload,optimizingdistortion

performance.Duetotheinputandoutputtransformers,the

–3dB bandwidth is reduced from 1.6GHz to 1.37GHz.

1.25V

0.1μF

V

OCM

4.99Ω

+IN

V

–

+

CM

IF IN

150Ω

+OUT

AIN

+OUTF

–OUTF

LTC6401-26

LTC2208

0.1μF

–IN

ENABLE

–OUT

37.4Ω

LTC2208 130Msps

16-Bit ADC

26dB GAIN

640126 F07

Figure 7. Single-Ended Input to LTC6401-26 and LTC2208

Figure 9. Top Silkscreen for DC987B, Test Circuit A

640126f

12

LTC6401-26

TYPICAL APPLICATION

Demo Circuit 987B Schematic (Test Circuit A)

V

CC

ENABLE

DIS

1

3

V

CC

2

JP1

C17

1000pF

C18

0.1μF

R16

0Ω

12

–

11

10

+

9

–

V

ENABLE

V

R10

R2

(1)

R14

(1)

86.6Ω

13

14

15

16

8

7

6

5

+IN

–IN

+OUT

+OUTF

–OUTF

–OUT

R6

R12

T2

R8

(1)

C2

0.1μF

C4

0Ω

R4

(2)

T1

(2)

5

4

1

2

3

2

1

TCM 4:19

1:4

4

J1

+IN

J4

+OUT

0.1μF

C21

0.1μF

R24

(1)

SL1

(2)

SL2

(2)

R7

(1)

LTC6401-26

R5

(1)

R11

(1)

SL3

0dB

6

(2)

J2

–IN

R3

(2)

C1

0.1μF

C3

0.1μF

J5

–OUT

R9

86.6Ω

–IN

V

R13

0Ω

C22

R1

0Ω

+

–

V

OCM

V

0.1μF

1

2

3

4

V

CC

C10

0.1μF

C9

1000pF

C12

1000pF

C13

0.1μF

V

CC

R19

1.5k

TP5

V

OCM

R20

1k

C7

0.1μF

T3

TCM 4:19

1:4

T4

TCM 4:19

1:4

R17

R18

0Ω

6

4

1

2

3

2

1

4

J6

TEST IN

J7

C23

C5

C19

0.1μF

C20

0.1μF

TEST OUT

0.1μF

R21

(1)

R22

(1)

R25

0Ω

R26

0Ω

C24

0.1μF

C6

0.1μF

6

V

CC

TP2

V

CC

NOTE: UNLESS OTHERWISE SPECIFIED.

(1) DO NOT STUFF.

C14

4.7μF

C15

1μF

2.85V TO 3.5V

(2) VERSION

-H

SL = SIGNAL LEVEL

IC

R3

R4

T1

SL1

SL2

SL3

TP3

GND

LTC6401UD-26 OPEN OPEN M/A-COM MABA-007159-000000 0dB

20dB 14dB

640126 TA02

640126f

13

LTC6401-26

TYPICAL APPLICATION

Test Circuit B, 4-Port Analysis

+

V

0.1μF

1000pF

–

+

–

V

ENABLE

V

12

G

11

10

9

BIAS CONTROL

R

F

500Ω

R

OUT

+IN

13

+OUT

37.4Ω

24.9Ω

25Ω

12.5Ω

PORT 1

PORT 3

8

(50Ω)

R

FILT

0.1μF

+OUTF

50Ω

+IN

–IN

IN+

IN–

OUT–

7

14

15

1/2

AGILENT

E5O71A

1/2

AGILENT

E5O71A

C

FILT

R

50Ω

FILT

1.7pF

–OUTF

–OUT

6

5

OUT+

R

G

25Ω

R

OUT

12.5Ω

F

–IN

16

500Ω

24.9Ω

37.4Ω

PORT 2

(50Ω)

PORT 4

(50Ω)

0.1μF

COMMON

MODE CONTROL

640126 TA03

1

2

3

4

+

–

V

OCM

1000pF

0.1μF

+

V

OCM

640126f

14

LTC6401-26

PACKAGE DESCRIPTION

UD Package

16-Lead Plastic QFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1691)

0.70 0.05

3.50 0.05

2.10 0.05

1.45 0.05

(4 SIDES)

PACKAGE OUTLINE

0.25 0.05

0.50 BSC

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

BOTTOM VIEW—EXPOSED PAD

PIN 1 NOTCH R = 0.20 TYP

OR 0.25 × 45° CHAMFER

R = 0.115

TYP

0.75 0.05

3.00 0.10

(4 SIDES)

15 16

PIN 1

TOP MARK

(NOTE 6)

0.40 0.10

1

2

1.45 0.10

(4-SIDES)

(UD16) QFN 0904

0.200 REF

0.25 0.05

0.50 BSC

0.00 – 0.05

NOTE:

1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION

ON THE TOP AND BOTTOM OF PACKAGE

640126f

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

15

LTC6401-26

RELATED PARTS

PART NUMBER DESCRIPTION

COMMENTS

High-Speed Differential Ampliﬁers/Differential Op Amps

LT^®1993-2

LT1993-4

LT1993-10

LT1994

800MHz Differential Ampliﬁer/ADC Driver

900MHz Differential Ampliﬁer/ADC Driver

700MHz Differential Ampliﬁer/ADC Driver

Low Noise, Low Distortion Differential Op Amp

A = 2V/V, OIP3 = 38dBm at 70MHz

V

A = 4V/V, OIP3 = 40dBm at 70MHz

V

A = 2V/V, OIP3 = 40dBm at 70MHz

V

16-Bit SNR and SFDR at 1MHz, Rail-to-Rail Outputs

LT5514

Ultralow Distortion IF Ampliﬁer/ADC Driver with Digitally

Controlled Gain

OIP3 = 47dBm at 100MHz, Gain Control Range 10.5dB to 33dB

LT5524

Low Distortion IF Ampliﬁer/ADC Driver with Digitally

Controlled Gain

OIP3 = 40dBm at 100MHz, Gain Control Range 4.5dB to 37dB

LTC6400-20

LTC6400-26

LTC6401-8

LTC6401-20

LT6402-6

1.8GHz Low Noise, Low Distortion, Differential ADC Driver

1.9GHz Low Noise, Low Distortion, Differential ADC Driver

2.2GHz Low Noise, Low Distortion, Differential ADC Driver

1.3GHz Low Noise, Low Distortion, Differential ADC Driver

300MHz Differential Ampliﬁer/ADC Driver

A = 20dB, 90mA Supply Current, IMD3 = –65dBc at 300MHz

V

A = 26dB, 85mA Supply Current, IMD3 = –71dBc at 300MHz

V

A = 8dB, 45mA Supply Current, IMD3 = –80dBc at 140MHz

V

A = 20dB, 50mA Supply Current, IMD3 = –74dBc at 140MHz

V

A = 6dB, Distortion < –80dBc at 25MHz

V

LT6402-12

LT6402-20

LTC6406

300MHz Differential Ampliﬁer/ADC Driver

A = 12dB, Distortion < –80dBc at 25MHz

V

300MHz Differential Ampliﬁer/ADC Driver

A = 20dB, Distortion < –80dBc at 25MHz

V

3GHz Rail-to-Rail Input Differential Op Amp

1.6nV/√Hz Noise, –72dBc Distortion at 50MHz, 18mA

LT6411

Low Power Differential ADC Driver/Dual Selectable Gain

Ampliﬁer

16mA Supply Current, IMD3 = –83dBc at 70MHz, A = 1, –1 or 2

V

High-Speed Single-Ended Output Op Amps

LT1812/LT1813/ High Slew Rate Low Cost Single/Dual/Quad Op Amps

LT1814

8nV/√Hz Noise, 750V/μs, 3mA Supply Current

6nV/√Hz Noise, 1500V/μs, 6.5mA Supply Current

6nV/√Hz Noise, 2500V/μs, 9mA Supply Current

LT1815/LT1816/ Very High Slew Rate Low Cost Single/Dual/Quad Op Amps

LT1817

LT1818/LT1819 Ultra High Slew Rate Low Cost Single/Dual Op Amps

LT6200/LT6201 Rail-to-Rail Input and Output Low Noise Single/Dual Op Amps 0.95nV/√Hz Noise, 165MHz GBW, Distortion = –80dBc at 1MHz

LT6202/LT6203/ Rail-to-Rail Input and Output Low Noise Single/Dual/Quad

LT6204 Op Amps

1.9nV/√Hz Noise, 3mA Supply Current, 100MHz GBW

1.1nV/√Hz Noise, 3.5mA Supply Current, 215MHz GBW

1.9nV/√Hz Noise, 1.2mA Supply Current, 60MHz GBW

LT6230/LT6231/ Rail-to-Rail Output Low Noise Single/Dual/Quad Op Amps

LT6232

LT6233/LT6234/ Rail-to-Rail Output Low Noise Single/Dual/Quad Op Amps

LT6235

Integrated Filters

LTC1562-2

LT1568

Very Low Noise, 8th Order Filter Building Block

Very Low Noise, 4th Order Filter Building Block

Linear Phase, Tunable 10th Order Lowpass Filter

Very Low Noise Differential 2.5MHz Lowpass Filter

Very Low Noise Differential 5MHz Lowpass Filter

Very Low Noise Differential 10MHz Lowpass Filter

Very Low Noise Differential 15MHz Lowpass Filter

Very Low Noise Differential 20MHz Lowpass Filter

Lowpass and Bandpass Filters up to 300kHz

Lowpass and Bandpass Filters up to 10MHz

Single-Resistor Programmable Cut-Off to 300kHz

SNR = 86dB at 3V Supply, 4th Order Filter

SNR = 82dB at 3V Supply, 4th Order Filter

SNR = 76dB at 3V Supply, 4th Order Filter

LTC1569-7

LT6600-2.5

LT6600-5

LT6600-10

LT6600-15

LT6600-20

640126f

LT 0108 • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

16

●

(408) 432-1900 FAX: (408) 434-0507 www.linear.com


型号：	LTC6401-26
厂家：	Linear
描述：	1.6GHz Low Noise, Low Distortion Differential ADC Driver for DC-140MHz 1.6GHz的低噪声，低失真差分ADC驱动器为DC- 140MHz的驱动器
文件：	总16页 (文件大小：224K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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