LTC6401IUD-8#PBF_技术文档

LTC6401-8

2.2GHz Low Noise, Low

Distortion Differential ADC

Driver for DC-140MHz

FEATURES

DESCRIPTION

The LTC^®6401-8 is a high-speed differential ampliﬁer tar-

geted at processing signals from DC to 140MHz. The part

has been speciﬁcally designed to drive 12-, 14- and 16-bit

ADCs with low noise and low distortion, but can also be

used as a general-purpose broadband gain block.

■

2.2GHz –3dB Bandwidth

■

Fixed Gain of 2.5V/V (8dB)

■

–92dBc IMD3 at 70MHz (Equivalent OIP3 = 50dBm)

■

–80.5dBc IMD3 at 140MHz (Equivalent OIP3 = 44dBm)

■

1nV/√Hz Internal Op Amp Noise

■

12.1dB Noise Figure

The LTC6401-8 is easy to use, with minimal support cir-

cuitry required. The output common mode voltage is set

using an external pin, independent of the inputs, which

eliminates the need for transformers or AC-coupling ca-

pacitors in many applications. The gain is internally ﬁxed

at 8dB (2.5V/V).

■

Differential Inputs and Outputs

■

400Ω Input Impedance

■

2.85V to 3.5V Supply Voltage

■

45mA Supply Current (135mW)

■

1V to 1.6V Output Common Mode, Adjustable

■

DC- or AC-Coupled Operation

Max Differential Output Swing 4.6V

■

The LTC6401-8 saves space and power compared to al-

ternative solutions using IF gain blocks and transformers.

The LTC6401-8 is packaged in a compact 16-lead 3mm ×

3mm QFN package and operates over the –40°C to 85°C

temperature range.

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

3.3V

Equivalent Output IP3 vs Frequency

60

(NOTE 7)

C2

0.1μF

C1

1000pF

C

F2

33pF

50

40

+

V

C3

0.1μF

R

S3

S1

15Ω

10Ω

V

+

–

DD

+OUT

AIN

V

+IN

IN

30

20

10

0

R1

59.0Ω

L1

24nH

C

C4

0.1μF

F1

LTC6401-8

–OUT

LTC2208

R

15Ω

R

33pF

S2

S4

10Ω

–IN

V

CM

OCM

R2

C

F3

33pF

–

COILCRAFT

0603CS

27.4Ω

LTC2208

130Msps

V

1.25V

16-Bit ADC

64018 TA01a

0

20 40 60 80 100 120 140 160 180 200

C5

0.1μF

R3

100Ω

FREQUENCY (MHz)

64018 TA01b

64018f

1

LTC6401-8

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Note 1)

TOP VIEW

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

CC

EE

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

Operating Temperature Range

(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

16 15 14 13

+

–

V

1

2

3

4

12 V

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-8#PBF

LTC6401IUD-8#PBF

TAPE AND REEL

PART MARKING* PACKAGE DESCRIPTION

SPECIFIED TEMPERATURE RANGE

16-Lead (3mm × 3mm) Plastic QFN 0°C to 70°C

16-Lead (3mm × 3mm) Plastic QFN –40°C to 85°C

LTC6401CUD-8#TRPBF

LTC6401IUD-8#TRPBF

LCCY

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 LTC6400 shows higher linearity especially at input frequency above 140MHz at the expense of higher supply current.

Please refer to the separate LTC6400 data sheets for complete details. Other gain versions from 8dB to 14dB will follow.

64018f

2

LTC6401-8

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

●

G

Gain

V

= 400mV Differential

7.5

8

8.5

dB

mdB/°C

mV

DIFF

IN

TC

Gain Temperature Drift

–0.5

89

GAIN

IN

V

Output Swing Low

Each Output, V = 1.6V Differential

170

SWINGMIN

SWINGMAX

OUTDIFFMAX

OUT

IN

Output Swing High

Each Output, V = 1.6V Differential

2.3

2.42

4.6

V

IN

Maximum Differential Output Swing

Output Current Drive

1dB Compressed

V

P-P

I

V

> 2V

10

–4

mA

mV

μV/°C

V

OUT

P-P,DIFF

V

Input Offset Voltage

Differential

4

1

OS

TCV

Input Offset Voltage Drift

Input Common Mode Voltage Range, MIN

Input Common Mode Voltage Range, MAX

Input Resistance (+IN, –IN)

Input Capacitance (+IN, –IN)

Output Resistance (+OUT, –OUT)

Filtered Output Resistance (+OUTF, –OUTF)

3

OS

VRMIN

VRMAX

I

1.6

V

●

Ω

R

Differential

340

400

1

460

INDIFF

C

Differential, Includes Parasitic

Differential

pF

●

Ω

R

18

85

25

32

OUTDIFF

OUTFDIFF

Ω

Differential

100

2.7

55

115

C

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

Common Mode Rejection Ratio Input Common Mode Voltage 1.1V~1.4V

Output Common Mode Voltage Control

pF

●

CMRR

36

dB

G

Common Mode Gain

V

OCM

= 1V to 1.6V

1

V/V

CM

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

OCM

= 1.1V to 1.5V

–15

15

mV

μV/°C

μA

OSCM

TCV

Common Mode Offset Voltage Drift

5

OSCM

IV

V

Input Current

OCM

3.6

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

4

μA

1.4

Power Supply

●

V

Operating Supply Range

Supply Current

2.85

36

3

3.5

60

3

V

mA

dB

S

I

ENABLE = 0.8V, Input and Output Floating

ENABLE = 2.4V, Input and Output Floating

45

S

Shutdown Supply Current

0.8

73.5

SHDN

+

PSRR

Power Supply Rejection Ratio

(Differential Outputs)

V = 2.85V to 3.5V

50

64018f

3

LTC6401-8

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

2.22

0.43

0.22

12.2

3400

2.3

MAX

UNITS

GHz

kHz

V/μs

ns

–3dB Bandwidth

200mV

(Note 6)

1

P-P,OUT

Bandwidth for 0.5dB Flatness

Bandwidth for 0.1dB Flatness

1/f Noise Corner

SR

Slew Rate

V

OUT

V

OUT

V

OUT

V

OUT

= 2V Step (Note 6)

t

1% Settling Time

Overdrive Recovery Time

Turn-On Time

= 2V (Note 6)

P-P

S1%

OVDR

ON

= 1.9V (Note 6)

18

ns

P-P

Within 10% of Final Values

79

ns

Turn-Off Time

I

Falls to 10% of Nominal

CC

193

14

ns

OFF

–3dBBW

V

Pin Small Signal –3dB BW

0.1V at V , Measured Single-Ended at

OCM

MHz

VOCM

OCM

P-P

Output (Note 6)

10MHz Input Signal

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

V

= 2V , R = 200Ω

–109/–88

–118/–100

–88

dBc

dBm

OUT

P-P

L

= 2V , No R

P-P

L

IMD3,10M

Third-Order Intermodulation

(f1 = 9.5MHz f2 = 10.5MHz)

V

= 2V Composite, R = 200Ω

P-P L

= 2V Composite, No R

–93

P-P

L

OIP3,10M

Equivalent Third-Order Output Intercept

Point (f1 = 9.5MHz f2 = 10.5MHz)

= 2V Composite, No R (Note 7)

50.7

P-P

L

P1dB,10M

NF10M

1dB Compression Point

R = 375Ω (Notes 5, 7)

17.8

12.1

3.2

8

dBm

dB

L

Noise Figure

R = 375Ω (Note 5)

L

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

V

= 2V , R = 200Ω

–91/–72

–100/–87

–83

dBc

dBm

OUT

P-P

L

= 2V , No R

P-P

L

IMD3,70M

Third-Order Intermodulation

(f1 = 69.5MHz f2 = 70.5MHz)

V

= 2V Composite, R = 200Ω

P-P L

= 2V Composite, No R

–92

P-P

L

OIP3,70M

Equivalent Third-Order Output Intercept

Point (f1 = 69.5MHz f2 = 70.5MHz)

= 2V Composite, No R (Note 7)

50

P-P

L

P1dB,70M

NF70M

1dB Compression Point

R = 375Ω (Notes 5, 7)

18.3

12.2

3.2

dBm

dB

L

Noise Figure

R = 375Ω (Note 5)

L

e

Input Referred Voltage Noise Density

Output Referred Voltage Noise Density

Includes Resistors (Short Inputs)

nV/√Hz

IN,70M

7.9

ON,70M

64018f

4

LTC6401-8

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

V

= 2V , R = 200Ω

–78/–59

–87/–70

–71

dBc

dBm

OUT

P-P

L

= 2V , No R

P-P

L

IMD3,140M

Third-Order Intermodulation

V

= 2V Composite, R = 200Ω

P-P L

(f1 = 139.5MHz f2 = 140.5MHz)

= 2V Composite, No R

–80

P-P

L

OIP3,140M

Equivalent Third-Order Output Intercept

Point (f1 = 139.5MHz f2 = 140.5MHz)

= 2V Composite, No R (Note 7)

44.2

P-P

L

P1dB,140M

NF140M

1dB Compression Point

R = 375Ω (Notes 5, 7)

18.7

12.3

3.1

dBm

dB

L

Noise Figure

R = 375Ω (Note 5)

L

e

Input Referred Voltage Noise Density

Output Referred Voltage Noise Density

Includes Resistors (Short Inputs)

nV/√Hz

dBc

IN,140M

ON,140M

7.9

IMD3,130M/150M Third-Order Intermodulation

(f1 = 130MHz f2 = 150MHz) Measure at

170MHz

V

= 2V Composite, R = 375Ω

–75

–67

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.

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

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 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.

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

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

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

L

Note 7: Since the LTC6401-8 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

LTC6401-8 with ampliﬁers that require 50Ω output load, the LTC6401-8

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

output voltage swing driving a given R is converted to OIP3 and P as

if it were driving a 50Ω load. Using this modiﬁed convention, 2V is by

P-P

L 1dB

deﬁnition equal to 10dBm, regardless of actual R .

L

TYPICAL PERFORMANCE CHARACTERISTICS

S21 Phase and Group Delay vs

Frequency

Frequency Response

Gain 0.1dB Flatness

14

12

10

8

1.0

0.8

0

–50

0.7

0.6

0.5

0.4

0.3

TEST CIRCUIT B

0.6

0.4

6

0.2

4

0

–100

–150

–200

2

–0.2

–0.4

–0.6

–0.8

–1.0

0

–2

–4

–6

PHASE

GROUP DELAY

10

100

1000

3000

10

100

1000

3000

0

200

400

600

800

1000

FREQUENCY (MHz)

64018 G01

64018 G02

64018 G03

64018f

5

LTC6401-8

TYPICAL PERFORMANCE CHARACTERISTICS

Input and Output Reﬂection and

Reverse Isolation vs Frequency

Input and Output Impedance vs

Frequency

PSRR and CMRR vs Frequency

0

–10

–20

–30

–40

–50

–60

–70

–80

500

450

400

350

300

250

200

150

100

50

100

80

70

60

50

40

30

20

10

0

TEST CIRCUIT B

PHASE

PSRR

IMPEDANCE MAGNITUDE

60

Z

IN

S11

S22

40

CMRR

Z

20

OUT

0

–20

–40

–60

–80

–100

Z

IN

S12

Z

OUT

0

10

100

1000

3000

10

100

FREQUENCY (MHz)

1000

1

10

100

1000

FREQUENCY (MHz)

64018 G04

64018 G05

64018 G06

Noise Figure and Input Referred

Noise Voltage vs Frequency

Small Signal Transient Response

Large Signal Transient Response

1.35

2.5

2.0

1.5

1.0

0.5

0

20

18

16

14

12

10

5

4

3

2

1

0

R

= 87.5Ω PER OUTPUT

R = 87.5Ω PER OUTPUT

L

TEST CIRCUIT B

L

TEST CIRCUIT B

1.30

1.25

1.20

1.15

+OUT

–OUT

EN

+OUT

–OUT

NOISE FIGURE

0

2

4

6

8

10

0

4

8

12

16

20

10

100

1000

TIME (ns)

FREQUENCY (MHz)

64018 G08

64018 G09

64018 G07

1% Settling Time for 2V

Output Step

Overdrive Recovery Response

Harmonic Distortion vs Frequency

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

5

–40

–50

4

3

R

= 87.5Ω PER OUTPUT

DIFFERENTIAL INPUT

L

+IN

TEST CIRCUIT B

V

= 2V

OUT P-P

4

3

2

–60

2

1

0

–70

–IN

0

–1

–2

–3

–4

–5

–6

R

= 87.5Ω PER OUTPUT

L

–80

+OUT

–1

–2

–3

–4

–5

–90

HD2 NO R

L

HD2 200Ω R

L

–100

–110

HD3 NO R

HD3 200Ω R

L

–OUT

TEST CIRCUIT B

25

0

1

2

3

4

5

0

20 40 60 80 100 120 140 160 180 200

0

50

75

100

125

TIME (ns)

FREQUENCY (MHz)

TIME (ns)

64018 G11

64018 G12

64018 G10

64018f

6

LTC6401-8

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

OUT P-P

SINGLE-ENDED INPUT

V

= 2V COMPOSITE

V = 2V COMPOSITE

V

= 2V

OUT

P-P

OUT

P-P

–60

200Ω R

L

200Ω R

–70

L

–80

NO R

L

NO R

L

–90

HD2 NO R

L

HD2 200Ω R

L

–100

–110

–100

–110

–100

–110

HD3 NO R

HD3 200Ω R

L

0

20 40 60 80 100 120 140 160 180 200

0

20 40 60 80 100 120 140 160 180 200

0

20 40 60 80 100 120 140 160 180 200

FREQUENCY (MHz)

64018 G13

64018 G14

64018 G15

Equivalent Output 1dB

Compression Point vs Frequency

Equivalent Output Third Order

Intercept Point vs Frequency

20

19

18

17

16

15

60

50

40

30

20

10

0

DIFFERENTIAL INPUT

R

= 375Ω

L

TEST CIRCUIT A (NOTE 7)

NO R

L

200Ω R

L

DIFFERENTIAL INPUT

(NOTE 7)

0

20 40 60 80 100 120 140 160 180 200

0

20 40 60 80 100 120 140 160 180 200

FREQUENCY (MHz)

64018 G16

64018 G17

Turn-On Time

Turn-Off Time

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

70

60

50

40

30

20

10

0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

70

60

50

40

30

20

10

0

R

L

= 87.5Ω PER OUTPUT

I

CC

+OUT

–OUT

+OUT

I

CC

ENABLE

400

R

= 87.5Ω PER OUTPUT

L

–0.5

–10

–0.5

–10

–100

0

100

200

300

500

–100

0

100

200

TIME (ns)

300

400

500

TIME (ns)

64018 G18

64018 G19

64018f

7

LTC6401-8

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. A 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 resistors, R

12.5Ω.

–

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

R

OUT

G

+IN

13

+OUT

500Ω

200Ω

12.5Ω

8

7

R

FILT

+OUTF

50Ω

+IN

–IN

IN+

IN–

OUT–

14

15

C

FILT

R

FILT

2.7pF

–OUTF

–OUT

50Ω

6

5

OUT+

R

G

200Ω

R

OUT

12.5Ω

F

–IN

16

500Ω

2k

COMMON

MODE CONTROL

5.3pF

64018 BD

1

2

3

4

+

–

V

OCM

64018f

8

LTC6401-8

APPLICATIONS INFORMATION

Circuit Operation

Input Impedance and Matching

The LTC6401-8 is a low noise and low distortion fully

differential op amp/ADC driver with:

ThedifferentialinputimpedanceoftheLTC6401-8is400Ω.

Usually the differential inputs need to be terminated to a

lower value impedance, e.g. 50Ω, in order to provide an

impedancematchforthesource.Severalchoicesareavail-

able. One approach is to use a differential shunt resistor

(Figure 1). Another approach is to employ a wideband

transformer and shunt resistor (Figure 2). Both methods

provide a wideband match. The termination resistor or

the transformer must be placed close to the input pins in

order to minimize the reﬂection due to input mismatch.

Alternatively, one could apply a narrowband impedance

match at the inputs of the LTC6401-8 for frequency selec-

tion and/or noise reduction.

• Operation from DC to 2.2GHz –3dB bandwidth

• Fixed gain of 2.5V/V (8dB)

• Differential input impedance 400Ω

• Differential output impedance 25Ω

• Differential impedance of output ﬁlter 100Ω

TheLTC6401-8iscomposedofafullydifferentialampliﬁer

with on chip feedback and output common mode voltage

control circuitry. Differential gain and input impedance

are set by 200Ω/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.

LTC6401-8

500Ω

25Ω

200Ω

12.5Ω

50Ω

13 +IN

+OUT

8

7

IN+

IN–

OUT–

+OUTF

V

IN

14 +IN

+

57.6Ω

–

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.

50Ω

2.7pF

15 –IN

–OUTF

6

5

OUT+

500Ω

25Ω

200Ω

12.5Ω

16 –IN

–OUT

64018 F01

Figure 1. Input Termination for Differential 50Ω Input Impedance

The LTC6401-8 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

Using Shunt Resistor

LTC6401-8

500Ω

25Ω

200Ω

12.5Ω

50Ω

13 +IN

14 +IN

+OUT

8

7

1:4

isautomaticallybiasedapproximately250mVaboveV

IN+

IN–

OUT–

OCM

+OUTF

V

IN

•

and thus no external circuitry is needed for bias. The

+

402Ω

–

•

50Ω

2.7pF

LTC6401-8 provides an output common mode voltage

15 –IN

–OUTF

6

5

OUT+

500Ω

set by V , which allows driving ADC directly without

OCM

25Ω

200Ω

12.5Ω

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.

16 –IN

–OUT

64018 F02

MINI CIRCUITS

TCM4-19

Figure 2. Input Termination for Differential 50Ω Input Impedance

Using a Balun

64018f

9

LTC6401-8

APPLICATIONS INFORMATION

LTC6401-8

+OUT

Referring to Figure 3, LTC6401-8 can be easily conﬁgured

for single-ended input and differential output without a

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

matching network while the other input is connected to

thesamematchingnetworkandasourceresistor.Because

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

two outputs have the same gain and thus symmetrical

swing. In general, the single-ended input impedance and

500Ω

1/2 R

200Ω

12.5Ω

50Ω

1/2 R

L

S

13 +IN

8

7

IN+

IN–

OUT–

+OUTF

V

IN

14 +IN

15 –IN

V

OUT

+

–

50Ω

2.7pF

–OUTF

6

5

OUT+

500Ω

1/2 R

200Ω

12.5Ω

1/2 R

L

S

16 –IN

–OUT

64018 F04

terminationresistorR aredeterminedbythecombination

T

Figure 4. Calculate Differential Gain

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

S

G

F

S

that the single-ended input impedance is 322Ω and R is

T

and noise is obvious when constant noise ﬁgure circle

and constant gain circle are plotted within the input Smith

Chart,basedonwhichuserscanchoosetheoptimalsource

impedance for a given gain and noise requirement.

59Ω in order to match to a 50Ω source impedance.

R

LTC6401-8

S

0.1μF

500Ω

50Ω

200Ω

12.5Ω

50Ω

13 +IN

+OUT

8

7

V

IN

+

–

R

T

Output Impedance Match and Filter

IN+

IN–

OUT–

59.0Ω

+OUTF

14 +IN

15 –IN

0.1μF

The LTC6401-8 can drive an ADC directly without external

output impedance matching. Alternatively, the differential

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

by series resistors or LC network.

50Ω

2.7pF

–OUTF

6

5

OUT+

500Ω

0.1μF

200Ω

12.5Ω

16 –IN

–OUT

64018 F03

27.4Ω

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

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

can reduce the lowpass ﬁlter bandwidth as shown in

Figure 5. A bandpass ﬁlter is easily implemented with

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

Impedance

The LTC6401-8 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:

LTC6401-8

500Ω

200Ω

12.5Ω

50Ω

13 +IN

+OUT

8

7

8pF

FILTERED OUTPUT

IN+

IN–

OUT–

+OUTF

14 +IN

15 –IN

12pF

(87.5MHz)

V_OUT

R_L

R_S+ 400 25+R_L

50Ω

1000

2.7pF

A_V=

=

•

–OUTF

6

5

OUT+

500Ω

V

8pF

IN

200Ω

12.5Ω

16 –IN

–OUT

The noise performance of the LTC6401-8 also depends

uponthesourceimpedanceandtermination. Forexample,

an input 1:4 transformer in Figure 2 improves SNR by

adding 6dB gain at the inputs. A trade-off between gain

64018 F05

Figure 5. LTC6401-8 Internal Filter Topology Modiﬁed for Low

Filter Bandwidth (Three External Capacitors)

64018f

10

LTC6401-8

APPLICATIONS INFORMATION

1.25V

only a few components as shown in Figure 6. Three

39pF capacitors and a 16nH inductor create a bandpass

ﬁlter with 165MHz center frequency, –3dB frequencies at

138MHz and 200MHz.

0.1μF

V

OCM

+OUT

+OUTF

4.99Ω

V

–

+

CM

IF IN

59.0Ω

+IN

AIN

LTC6401-8

LTC2208

–OUTF

39pF

–IN

ENABLE

–OUT

AIN

LTC6401-8

12.5Ω

4.99Ω

500Ω

200Ω

10Ω

4.99Ω

27.4Ω

LTC2208 130Msps

16-Bit ADC

13 +IN

+OUT

8

7

8dB GAIN

64018 F07

50Ω

IN+

IN–

OUT–

+OUTF

14 +IN

15 –IN

Figure 7. Single-Ended Input to LTC6401-8 and LTC2208

16nH

LTC2208

1.7pF

39pF

50Ω

OUT+

500Ω

–OUTF

6

5

LTC6401-8 with single-ended input driving the LTC2208,

whichisa16-bit,130MspsADC.Twoexternal5Ωresistors

help eliminate potential resonance associated with bond

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

of the LTC6401-8 is connected to V of the LTC2208 at

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

converted to differential signal via a balun and fed to the

input of the LTC6401-8.

200Ω

12.5Ω

10Ω

4.99Ω

16 –IN

–OUT

64018 F06

39pF

OCM

Figure 6. LTC6401-8 Modiﬁed 165MHz for Bandpass Filtering

(Three External Capacitors, One External Inductor)

CM

Output Common Mode Adjustment

The LTC6401-8’s output common mode voltage is set

Figure 8 summarizes the IMD3 performance of the whole

system as shown in Figure 7.

by the V

pin, which is a high impedance input. The

OCM

output common mode voltage is capable of tracking V

OCM

control is

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

–40

OCM

SINGLE-ENDED INPUT

typically 14MHz, which is dominated by a low pass ﬁlter

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

F

= 122.8Msps

S

–50

–60

DRIVER V

= 2V COMPOSITE

OUT

P-P

OCM

mon mode noise generation at the outputs. The internal

common mode feedback loop has a –3dB bandwidth

around 400MHz, allowing fast rejection of any common

–70

–80

mode output voltage disturbance. The V

pin should

OCM

–90

be tied to a DC bias voltage with a 0.1μF bypass capaci-

tor. When interfacing with 3V A/D converters such as the

–100

–110

LT22xx families, the V

pin can be connected to the

OCM

V

pin of the ADC.

0

20 40 60 80 100 120 140 160 180 200

CM

FREQUENCY (MHz)

64018 F08

Driving A/D Converters

Figure 8. IMD3 for the Combination of LTC6401-8 and LTC2208

TheLTC6401-8hasbeenspeciﬁcallydesignedtointerface

directlywithhighspeedA/Dconverters.Figure7showsthe

64018f

11

LTC6401-8

APPLICATIONS INFORMATION

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 LTC6401 with a 375Ω differential load, optimizing

distortionperformance. Duetotheinputandoutputtrans-

formers, the –3dB bandwidth is reduced from 2.2GHz to

approximately 1.65GHz.

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.

Figure 9. Top Silkscreen for DC987B. Test Circuit A

64018f

12

LTC6401-8

TYPICAL APPLICATIONS

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

0Ω

R12

0Ω

T2

TCM 4:19

1:4

R8

(1)

C2

0.1μF

C4

R4

(2)

T1

(2)

6

4

1

2

3

2

1

4

6

J1

+IN

J4

+OUT

0.1μF

C21

0.1μF

R24

(1)

SL1

(2)

SL2

(2)

R7

(1)

LTC6401-8

R5

(1)

R11

(1)

SL3

(2)

J5

–OUT

0dB

J2

–IN

R3

(2)

C1

0.1μF

C3

0.1μF

R9

86.6Ω

–IN

V

R13

0Ω

C22

R1

0Ω

+

–

V

0.1μF

OCM

1

2

3

4

V

CC

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

-E

SL = SIGNAL LEVEL

IC

R3

R4

T1

SL1

SL2

SL3

2dB

TP3

GND

LTC6401CUD-8 200Ω 200Ω MINI-CIRCUITS TCM4-19 (1:4) 6dB

8dB

64018 TA02

64018f

13

LTC6401-8

TYPICAL APPLICATIONS

Test Circuit B, 4-Port Analysis

+

V

1000pF

0.1μF

–

+

–

V

ENABLE

V

12

G

11

10

9

BIAS CONTROL

R

F

500Ω

R

OUT

+IN

13

+OUT

37.4Ω

200Ω

12.5Ω

PORT 1

(50Ω)

PORT 3

(50Ω)

8

7

R

FILT

50Ω

0.1μF

+OUTF

+IN

–IN

IN+

IN–

OUT–

14

15

1/2

AGILENT

E5O71A

1/2

AGILENT

E5O71A

C

FILT

2.7pF

R

50Ω

FILT

133Ω

–OUTF

–OUT

6

5

OUT+

R

G

200Ω

R

OUT

12.5Ω

F

–IN

16

500Ω

37.4Ω

PORT 2

(50Ω)

PORT 4

(50Ω)

0.1μF

COMMON

MODE CONTROL

64018 TA03

1

2

3

4

+

–

V

OCM

1000pF

0.1μF

+

V

OCM

64018f

14

LTC6401-8

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

64018f

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

LTC6401-8

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 = 10V/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

LTC6401-20

LTC6401-26

LT6402-6

1.8GHz Low Noise, Low Distortion, Differential ADC Driver

1.9GHz Low Noise, Low Distortion, Differential ADC Driver

1.3GHz Low Noise, Low Distortion, Differential ADC Driver

1.6GHz 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 = 20dB, 50mA Supply Current, IMD3 = –74dBc at 140MHz

V

A = 26dB, 45mA Supply Current, IMD3 = –72dBc at 140MHz

V

A = 6dB, Distortion < –80dBc at 25MHz

V

LT6402-12

LT6402-20

LTC6404-1

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

600MHz Low Noise Differential ADC Driver

e = 1.5nV/√Hz, Rail-to-Rail Outputs

n

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

64018f

LT 1207 • 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：	LTC6401IUD-8#PBF
厂家：	Linear
描述：	LTC6401-8 - 2.2GHz Low Noise, Low Distortion Differential ADC Driver for DC-140MHz; Package: QFN; Pins: 16; Temperature Range: -40°C to 85°C 放大器
文件：	总16页 (文件大小：219K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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