LT6600CDF-10#TRPBF_技术文档

LT6600-10

Very Low Noise, Differential

Ampliﬁer and 10MHz Lowpass Filter

FEATURES

DESCRIPTION

TheLT^®6600-10combinesafullydifferentialampliﬁerwitha

4thorder10MHzlowpassﬁlterapproximatingaChebyshev

frequency response. Most differential ampliﬁers require

many precision external components to tailor gain and

n

Programmable Differential Gain via Two External

Resistors

n

Adjustable Output Common Mode Voltage

n

Operates and Speciﬁed with 3V, 5V, 5V Supplies

n

0.5dB Ripple 4th Order Lowpass Filter with 10MHz

Cutoff

bandwidth. In contrast, with the LT6600-10, two external

resistors program differential gain, and the ﬁlter’s 10MHz

cutoff frequency and passband ripple are internally set.

The LT6600-10 also provides the necessary level shifting

to set its output common mode voltage to accommodate

the reference voltage requirements of A/Ds.

n

82dB S/N with 3V Supply and 2V Output

P-P

Low Distortion, 2V , 800Ω Load

P-P

1MHz: 88dBc 2nd, 97dBc 3rd

5MHz: 74dBc 2nd, 77dBc 3rd

n

Fully Differential Inputs and Outputs

Compatible with Popular Differential Ampliﬁer Pinouts

SO-8 and DFN-12 Packages

Using a proprietary internal architecture, the LT6600-10

integrates an antialiasing ﬁlter and a differential ampli-

ﬁer/driver without compromising distortion or low noise

performance. At unity gain the measured in band signal-

to-noise ratio is an impressive 82dB. At higher gains the

input referred noise decreases so the part can process

smaller input differential signals without signiﬁcantly

degrading the output signal-to-noise ratio.

APPLICATIONS

n

High Speed ADC Antialiasing and DAC Smoothing in

Networking or Cellular Base Station Applications

n

High Speed Test and Measurement Equipment

n

Medical Imaging

The LT6600-10 also features low voltage operation. The

differential design provides outstanding performance for

n

Drop-In Replacement for Differential Ampliﬁers

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

a 2V signal level while the part operates with a single

P-P

3V supply.

For similar devices with other cutoff frequencies, refer to

the LT6600-20, LT6600-15, LT6600-5 and LT6600-2.5.

TYPICAL APPLICATION ^{(S8 pin numbers shown)}

An 8192 Point FFT Spectrum

0

INPUT IS A 4.7MHz SINEWAVE

–10

LT6600-10

5V

2V

SAMPLE

P-P

f

= 66MHz

–20

–30

–40

–50

–60

–70

–80

–90

–100

–110

0.1μF

5V

R

402Ω

IN

3

+

1

7

2

8

V

49.9Ω

–

4

+

V

MID

A

18pF

D

LTC1748

IN

OUT

–

V

0.01μF

OCM

–

5

V

+

IN

V

CM

R

6

IN

402Ω

1μF

GAIN = 402Ω/R

IN

0

4

8

12 16 20 24 28 32

FREQUENCY (MHz)

6600 TA01a

6600 TA01b

66001fe

1

LT6600-10

ABSOLUTE MAXIMUM RATINGS ^{(Note 1)}

Total Supply Voltage .................................................11V

Input Current (Note 8).......................................... 10mA

Operating Temperature Range (Note 6).... –40°C to 85°C

Speciﬁed Temperature Range (Note 7) .... –40°C to 85°C

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

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

Lead Temperature (Soldering, 10 sec) .................. 300°C

PIN CONFIGURATION

TOP VIEW

+

–

1

2

3

4

5

6

12 IN

IN

–

+

IN

1

2

3

4

8

7

6

5

IN

NC

V

NC

11

10

9

V

MID

OCM

+

V

OCM

MID

–

13

–

V

+

V

–

8

NC

+

–

OUT

–

7

OUT

S8 PACKAGE

8-LEAD PLASTIC SO

DF PACKAGE

12-LEAD (4mm s 4mm) PLASTIC DFN

T

JMAX

= 150°C, θ = 100°C/W

JA

T

= 150°C, θ = 43°C/W, θ = 4°C/W

JA JC

JMAX

–

EXPOSED PAD (PIN 13) IS V , MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

LT6600CS8-10#PBF

LT6600IS8-10#PBF

LT6600CDF-10#PBF

LT6600IDF-10#PBF

LEAD BASED FINISH

LT6600CS8-10

TAPE AND REEL

PART MARKING

660010

PACKAGE DESCRIPTION

8-Lead Plastic SO

TEMPERATURE RANGE

0°C to 70°C

LT6600CS8-10#TRPBF

LT6600IS8-10#TRPBF

LT6600CDF-10#TRPBF

LT6600IDF-10#TRPBF

TAPE AND REEL

600I10

8-Lead Plastic SO

–40°C to 85°C

0°C to 70°C

60010

12-Lead (4mm × 4mm) Plastic DFN

PACKAGE DESCRIPTION

8-Lead Plastic SO

60010

–40°C to 85°C

TEMPERATURE RANGE

0°C to 70°C

PART MARKING

660010

LT6600CS8#TR

LT6600IS8-10

LT6600IS8-10#TR

600I10

8-Lead Plastic SO

–40°C to 85°C

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based ﬁnish parts.

The temperature grade is identiﬁed by a label on the shipping container for the DFN Package.

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/

66001fe

2

LT6600-10

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the full operating temperature

range, otherwise speciﬁcations are at T_A= 25°C. Unless otherwise speciﬁed V_S= 5V (V⁺= 5V, V^–= 0V), R_IN= 402Ω, and R_LOAD= 1k.

PARAMETER

Filter Gain, V = 3V

CONDITIONS

= 2V , f = DC to 260kHz

MIN

–0.4

–0.1

–0.4

–0.3

–0.2

TYP

0

MAX

0.5

0.1

0.3

1

UNITS

dB

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

V

IN

S

P-P IN

l

= 2V , f = 1MHz (Gain Relative to 260kHz)

0

dB

P-P IN

= 2V , f = 5MHz (Gain Relative to 260kHz)

–0.1

0.1

0.3

–28

–44

0

dB

P-P IN

= 2V , f = 8MHz (Gain Relative to 260kHz)

dB

P-P IN

= 2V , f = 10MHz (Gain Relative to 260kHz)

1.7

–25

dB

P-P IN

= 2V , f = 30MHz (Gain Relative to 260kHz)

dB

P-P IN

= 2V , f = 50MHz (Gain Relative to 260kHz)

dB

P-P IN

Filter Gain, V = 5V

= 2V , f = DC to 260kHz

–0.5

–0.1

–0.4

–0.3

0.5

0.1

0.3

0.9

1.4

–25

dB

S

P-P IN

l

= 2V , f = 1MHz (Gain Relative to 260kHz)

0

dB

P-P IN

= 2V , f = 5MHz (Gain Relative to 260kHz)

–0.1

0.1

0.2

–28

–44

–0.1

12

dB

P-P IN

= 2V , f = 8MHz (Gain Relative to 260kHz)

dB

P-P IN

= 2V , f = 10MHz (Gain Relative to 260kHz)

dB

P-P IN

= 2V , f = 30MHz (Gain Relative to 260kHz)

dB

P-P IN

= 2V , f = 50MHz (Gain Relative to 260kHz)

dB

P-P IN

Filter Gain, V = 5V

= 2V , f = DC to 260kHz

–0.6

11.4

0.4

dB

S

P-P IN

Filter Gain, R = 100Ω, V = 3V, 5V, 5V

= 0.5V , f = DC to 260kHz

12.6

dB

IN

S

P-P IN

Filter Gain Temperature Coefﬁcient (Note 2)

f

= 260kHz, V = 2V

P-P

780

56

ppm/C

IN

Noise

Noise BW = 10kHz to 10MHz, R = 402Ω

μV

RMS

IN

Distortion (Note 4)

1MHz, 2V , R = 800Ω

2nd Harmonic

3rd Harmonic

88

97

dBc

P-P

L

5MHz, 2V , R = 800Ω

2nd Harmonic

3rd Harmonic

74

77

dBc

P-P

L

l

Differential Output Swing

Measured Between Pins 4 and 5

Pin 7 Shorted to Pin 2

V = 5V

S

3.85

5.0

4.9

V

S

P-P DIFF

V = 3V

l

Input Bias Current

Average of Pin 1 and Pin 8

–85

–40

μA

l

Input Referred Differential Offset

R

IN

= 402ꢀ

V = 3V

5

10

8

20

30

35

mV

S

V = 5V

S

V = 5V

S

l

R

IN

= 100ꢀ

V = 3V

5

13

22

30

mV

S

V = 5V

S

V = 5V

S

Differential Offset Drift

10

μV/°C

66001fe

3

LT6600-10

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the full operating temperature

range, otherwise speciﬁcations are at T_A= 25°C. Unless otherwise speciﬁed V_S= 5V (V⁺= 5V, V^–= 0V), R_IN= 402Ω, and R_LOAD= 1k.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

Input Common Mode Voltage (Note 3)

Differential Input = 500mV

IN

,

V = 3V

0.0

–2.5

1.5

3.0

1.0

V

P-P

S

R

= 100ꢀ

V = 5V

S

V = 5V

S

l

Output Common Mode Voltage (Note 5)

Differential Input = 2V

Pin 7 = OPEN

,

V = 3V

1.0

1.5

–1.0

1.5

3.0

2.0

V

P-P

S

V = 5V

S

V = 5V

S

l

Output Common Mode Offset

(With Respect to Pin 2)

V = 3V

–35

–40

–55

5

0

–5

40

35

mV

S

V = 5V

S

V = 5V

S

Common Mode Rejection Ratio

61

dB

l

Voltage at V

(Pin 7)

V = 5V (S8)

2.46

2.45

2.51

1.5

2.55

2.56

V

MID

S

V = 5V (DFN)

S

V = 3V

S

l

V

Input Resistance

Bias Current

4.3

5.5

7.7

kꢀ

MID

l

V

OCM

= V

= V /2

V = 5V

S

–15

–10

–3

μA

OCM

MID

S

V = 3V

Power Supply Current

V = 3V, V = 5V

35

39

43

46

mA

S

l

V = 3V, V = 3V

S

V = 5V

36

S

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 5: Output common mode voltage is the average of the voltages at

Pins 4 and 5. The output common mode voltage is equal to the voltage

applied to V

.

OCM

Note 6: The LT6600C is guaranteed functional over the operating

Note 2: This is the temperature coefﬁcient of the internal feedback

temperature range –40°C to 85°C.

resistors assuming a temperature independent external resistor (R ).

Note 3: The input common mode voltage is the average of the voltages

IN

Note 7: The LT6600C is guaranteed to meet 0°C to 70°C speciﬁcations and

is designed, characterized and expected to meet the extended temperature

limits, but is not tested at –40°C and 85°C. The LT6600I is guaranteed to

meet speciﬁed performance from –40°C to 85°C.

applied to the external resistors (R ). Speciﬁcation guaranteed for

IN

R

≥ 100Ω.

IN

Note 4: Distortion is measured differentially using a differential stimulus,

The input common mode voltage, the voltage at V , and the voltage at

Note 8: The inputs are protected by back-to-back diodes. If the differential

input voltage exceeds 1.4V, the input current should be limited to less than

10mA.

OCM

V

are equal to one half of the total power supply voltage.

MID

66001fe

4

LT6600-10

TYPICAL PERFORMANCE CHARACTERISTICS

Amplitude Response

Passband Gain and Group Delay

10

0

1

0

60

55

50

45

40

35

30

25

20

15

10

V

= 5V

S

GAIN = 1

–1

–2

–3

–4

–5

–6

–7

–8

–9

–10

–20

–30

–40

–50

–60

–70

–80

V

= 5V

S

GAIN = 1

= 25°C

T

A

100k

1M

10M

100M

0.5

5.3

10.1

14.9

FREQUENCY (Hz)

FREQUENCY (MHz)

6600 G01

6600 G02

Output Impedance

Passband Gain and Group Delay

vs Frequency (OUT⁺or OUT^–)

12

11

10

9

100

10

1

60

55

50

45

40

35

30

25

20

15

10

8

7

6

5

4

V

= 5V

S

GAIN = 4

3

T

= 25°C

A

0.1

2

100k

1M

10M

100M

0.5

5.3

10.1

14.9

FREQUENCY (Hz)

FREQUENCY (MHz)

6600 G04

6600 G03

Distortion vs Frequency

V

_IN= 2V_P-P, V_S= 3V, R_L= 800Ω

Common Mode Rejection Ratio

at Each Output, T_A= 25°C

Power Supply Rejection Ratio

80

75

70

65

60

55

50

45

40

35

90

80

70

60

50

40

30

20

10

0

–40

–50

–60

–70

–80

–90

–100

DIFFERENTIAL INPUT,

2ND HARMONIC

DIFFERENTIAL INPUT,

3RD HARMONIC

SINGLE-ENDED INPUT,

2ND HARMONIC

SINGLE-ENDED INPUT,

3RD HARMONIC

V

= 5V

S

GAIN = 1

= 1V

V

IN

= 25°C

P-P

T

A

V

A

V

= 3V

S

= 200mV

IN

P-P

T

= 25oC

+

TO DIFFOUT

100k

1M

10M

100M

1k

10k

100k

1M

10M

100M

0.1

1

10

FREQUENCY (Hz)

FREQUENCY (MHz)

FREQUENCY (Hz)

6600 G06

6600 G05

6600 G07

66001fe

5

LT6600-10

TYPICAL PERFORMANCE CHARACTERISTICS

Distortion vs Signal Level

V_S= 3V, R_L= 800Ω at Each

Output, T_A= 25°C

Distortion vs Signal Level

V_S= 5V, R_L= 800Ω at Each

Output, T_A= 25°C

Distortion vs Frequency

V_IN= 2V_P-P, V_S= 5V, R_L= 800Ω

at Each Output, T_A= 25°C

–40

–50

–40

–50

–40

–50

–60

–70

–80

–90

–100

2ND HARMONIC,

5MHz INPUT

3RD HARMONIC,

5MHz INPUT

2ND HARMONIC,

1MHz INPUT

3RD HARMONIC,

1MHZ INPUT

2ND HARMONIC,

5MHz INPUT

DIFFERENTIAL INPUT,

2ND HARMONIC

DIFFERENTIAL INPUT,

3RD HARMONIC

SINGLE-ENDED INPUT,

2ND HARMONIC

SINGLE-ENDED INPUT,

3RD HARMONIC

3RD HARMONIC,

5MHz INPUT

2ND HARMONIC,

1MHz INPUT

–60

–70

–60

–70

3RD HARMONIC,

1MHZ INPUT

–80

–90

–100

–110

–100

1

2

3

5

0

4

0

1

2

3

4

5

0.1

1

10

INPUT LEVEL (V

)

P-P

FREQUENCY (MHz)

INPUT LEVEL (V

)

P-P

6600 G08

6600 G10

6600 G09

Distortion vs Input Common Mode

Level, 0.5V_P-P, 1MHz Input, 4x Gain,

R_L= 800Ω at Each Output, T_A= 25°C

Distortion vs Input Common Mode

Level, 2V_P-P, 1MHz Input, 1x Gain,

R_L= 800Ω at Each Output, T_A= 25°C

Power Supply Current

vs Power Supply Voltage

–40

–50

–60

–70

–80

–90

–100

–40

–50

–60

–70

–80

–90

–100

40

38

36

34

32

30

28

26

24

2ND HARMONIC,

V

= 3V

V

= 3V

S

3RD HARMONIC,

= 3V

T

= 85°C

= 25°C

3RD HARMONIC,

= 3V

A

V

S

2ND HARMONIC,

= 5V

2ND HARMONIC,

= 5V

V

S

3RD HARMONIC,

= 5V

3RD HARMONIC,

= 5V

V

S

T

= –40°C

A

–3

–1

0

1

2

3

–2

–3

–1

INPUT COMMON MODE VOLTAGE

RELATIVE TO V (V)

0

1

2

3

2

3

4

5

6

7

8

9

10

–2

INPUT COMMON MODE VOLTAGE

TOTAL SUPPLY VOLTAGE (V)

RELATIVE TO V

(V)

MID

6600 G12

6600 G11

6600 G13

Transient Response,

Differential Gain = 1

Distortion vs Output Common Mode,

2V_P-P1MHz Input, 1x Gain, T_A= 25°C

–40

–50

–60

–70

–80

–90

–100

+

V

OUT

50mV/DIV

2ND HARMONIC, V = 3V

S

3RD HARMONIC, V = 3V

S

2ND HARMONIC, V = 5V

S

DIFFERENTIAL

INPUT

200mV/DIV

3RD HARMONIC, V = 5V

S

2ND HARMONIC, V

3RD HARMONIC, V

=

5V

S

6600 G14

100ns/DIV

–1

0

0.5

1

1.5

2

–0.5

OUTPUT COMMON MODE VOLTAGE (V)

6600 G15

66001fe

6

LT6600-10

PIN FUNCTIONS ^(DFN/S8)

–

+

IN and IN (Pins 1, 12/Pins 1, 8): Input Pins. Signals can

should be as close as possible to the IC. For dual supply

applications, bypass V to ground and V to ground with

a quality 0.1μF ceramic capacitor.

+

–

be applied to either or both input pins through identical

externalresistors,R .TheDCgainfromdifferentialinputs

IN

to the differential outputs is 1580Ω/R .

+

–

IN

OUT and OUT (Pins 6, 7/Pins 4, 5): Output Pins. These

aretheﬁlterdifferentialoutputs.Eachpincandrivea100Ω

and/or 50pF load to AC ground.

NC (Pin 2, 5, 11/NA): No Connection.

V

(Pin 3/Pin 2): Is the DC Common Mode Reference

OCM

Voltage for the 2nd Filter Stage. Its value programs the

commonmodevoltageofthedifferentialoutputoftheﬁlter.

This is a high impedance input, which can be driven from

V

(Pin 10/Pin 7): The V

pin is internally biased

MID

at mid-supply, see block diagram. For single-supply

operation the V

pin should be bypassed with a quality

MID

–

an external voltage reference, or can be tied to V on the

0.01μF ceramic capacitor to V . For dual supply operation,

MID

PCboard.V

shouldbebypassedwitha0.01μFceramic

V

can be bypassed or connected to a high quality DC

OCM

MID

capacitor unless it is connected to a ground plane.

ground. A ground plane should be used. A poor ground

will increase noise and distortion. V sets the output

+

–

MID

V andV (Pins4, 8, 9/Pins3, 6):PowerSupplyPins. For

common mode voltage of the 1st stage of the ﬁlter. It has

a 5.5kΩ impedance, and it can be overridden with an

external low impedance voltage source.

–

a single 3.3V or 5V supply (V grounded) a quality 0.1μF

ceramic bypass capacitor is required from the positive

+

–

supplypin(V )tothenegativesupplypin(V ). Thebypass

BLOCK DIAGRAM

R

IN

+

–

V

IN

V

OUT

V

IN

MID

+

V

11k

PROPRIETARY

LOWPASS

402Ω

FILTER STAGE

200Ω

–

V

OP AMP

200Ω

+

OCM

–

V

OCM

+

–

200Ω

402Ω

6600 BD

–

+

V

IN

OCM

V

OUT

R

IN

66001fe

7

LT6600-10

APPLICATIONS INFORMATION

Interfacing to the LT6600-10

Use Figure 4 to determine the interface between the

LT6600-10 and a current output DAC. The gain, or

Note: The referenced pin numbers correspond to the S8

package. See the Pin Functions section for the equivalent

DFN-12 package pin numbers.

“transimpedance”,isdeﬁnedasA=V /I Ω.Tocompute

OUT IN

the transimpedance, use the following equation:

402•R1

R1+R2

The LT6600-10 requires 2 equal external resistors, R , to

IN

A =

Ω

setthedifferential gainto402Ω/R .Theinputstotheﬁlter

IN

+

–

are the voltages V and V presented to these external

IN

By setting R1 + R2 = 402Ω, the gain equation reduces

to A = R1Ω.

+

components, Figure 1. The difference between V and

IN

–

+

V

is the differential input voltage. The average of V

IN

–

The voltage at the pins of the DAC is determined by R1,

and V

the voltages V

is the common mode input voltage. Similarly,

IN

+

–

R2, the voltage on V_MIDand the DAC output current (I_IN

and V

appearing at Pins 4 and 5

OUT

or I_IN^–). Consider Figure 4 with R1 = 49.9Ω and R2 =

of the LT6600-10 are the ﬁlter outputs. The difference

+

–

348Ω. The voltage at

DAC pins is given by:

V

is 1.65V. The voltage at the

betweenV

andV

isthedifferentialoutputvoltage.

MID

OUT

+

–

The average of V

output voltage.

and V

is the common mode

OUT

R1

R1•R2

V_DAC= V_PIN7

•

+I

R1+R2+ 402 ^INR1+R2

Figure 1 illustrates the LT6600-10 operating with a single

3.3V supply and unity passband gain; the input signal is

DC coupled. The common mode input voltage is 0.5V and

=103mV +I 43.6Ω

IN

–

+

the differential input voltage is 2V . The common mode

I

IN

is I_INor I_IN.The transimpedance in this example is

P-P

output voltage is 1.65V and the differential output voltage

50.4Ω.

is2V forfrequenciesbelow10MHz.Thecommonmode

P-P

Evaluating the LT6600-10

output voltage is determined by the voltage at V

. Since

OCM

V

is shorted to V

the output common mode is the

OCM

MID

The low impedance levels and high frequency operation

of the LT6600-10 require some attention to the matching

networks between the LT6600-10 and other devices. The

previousexamplesassumeanideal(0Ω)sourceimpedance

andalarge(1kΩ)loadresistance.Amongpracticalexamples

where impedance must be considered is the evaluation

of the LT6600-10 with a network analyzer. Figure 5

is a laboratory setup that can be used to characterize the

LT6600-10 using single-ended instruments with 50Ω

source impedance and 50Ω input impedance. For a unity

gain conﬁguration the LT6600-10 requires a 402Ω source

resistance yet the network analyzer output is calibrated

for a 50Ω load resistance. The 1:1 transformer, 53.6Ω

and 388Ω resistors satisfy the two constraints above.

The transformer converts the single-ended source into a

differential stimulus. Similarly, the output the LT6600-10

will have lower distortion with larger load resistance yet

the analyzer input is typically 50Ω. The 4:1 turns (16:1

impedance) transformer and the two 402Ω resistors of

mid-supply voltage. In addition, the common mode input

voltagecanbeequaltothemid-supplyvoltageofV (refer

MID

to the Distortion vs Input Common Mode Level graphs in

the Typical Performance Characteristics section).

Figure 2 shows how to AC couple signals into the

LT6600-10. In this instance, the input is a single-ended

signal.AC-couplingallowstheprocessingofsingle-ended

or differential signals with arbitrary common mode levels.

The 0.1μF coupling capacitor and the 402Ω gain setting

resistor form a high pass ﬁlter, attenuating signals below

4kHz.Largervaluesofcouplingcapacitorswillproportion-

ally reduce this highpass 3dB frequency.

In Figure 3 the LT6600-10 is providing 12dB of gain. The

gain resistor has an optional 62pF in parallel to improve

the passband ﬂatness near 10MHz. The common mode

output voltage is set to 2V.

66001fe

8

LT6600-10

APPLICATIONS INFORMATION

3.3V

0.1μF

4

V

3

–

402Ω

3

2

1

0

3

2

1

7

2

8

–

V

IN

+

–

+

–

V

+

V

OUT

LT6600-10

+

V

0.01μF

IN

V

OUT

1

0

–

+

5

V

+

IN

402Ω

6

t

–

6600 F01

V

IN

Figure 1. (S8 Pin Numbers)

3.3V

0.1μF

V

0.1μF

3

402Ω

1

7

2

8

3

2

1

0

2

1

–

4

+

–

V

+

OUT

V

OUT

LT6600-10

+

0.1μF

V

IN

0.01μF

V

–

OUT

–

0

t

OUT

+

5

V

+

IN

6

–1

6600 F02

Figure 2. (S8 Pin Numbers)

62pF

5V

0.1μF

V

3

100Ω

1

3

–

V

–

4

IN

+

–

+

V

OUT

+

7

OUT

LT6600-10

2

1

0

2

1

2

–

V

0.01μF

OUT

500mV (DIFF)

P-P

–

8

+

5

+

V

100Ω

IN

6

t

0

+

–

2V

–

6600 F03

IN

0.01μF

62pF

Figure 3. (S8 Pin Numbers)

CURRENT

OUTPUT

DAC

3.3V

0.1μF

4

–

+

3

R2

I

IN

1

7

2

8

–

+

–

+

V

OUT

R1

0.01μF

R2

LT6600-10

–

OUT

5

+

6

6600 F04

Figure 4. (S8 Pin Numbers)

66001fe

9

LT6600-10

APPLICATIONS INFORMATION

Figure5,presenttheoutputoftheLT6600-10witha1600Ω

differential load, or the equivalent of 800Ω to ground at

each output. The impedance seen by the network analyzer

input is still 50Ω, reducing reﬂections in the cabling be-

tween the transformer and analyzer input.

voltage of V . While the internal 11k resistors are well

MID

matched, their absolute value can vary by 20ꢁ. This

should be taken into consideration when connecting an

external resistor network to alter the voltage of V

.

MID

20

1dB PASSBAND GAIN

1MHz 25°C

COMPRESSION POINTS

2.5V

0

0.1μF

1MHz 85°C

COILCRAFT

TTWB-16A

4:1

COILCRAFT

TTWB-1010

–20

NETWORK

ANALYZER

SOURCE

NETWORK

ANALYZER

INPUT

3RD HARMONIC

3

85°C

388Ω

1:1

1

7

2

8

–40

402Ω

–

4

3RD HARMONIC

+

25°C

50Ω

LT6600-10

–60

53.6Ω

50Ω

2ND HARMONIC

85°C

–

–80

5

+

402Ω

2ND HARMONIC

25°C

388Ω

6

0.1μF

6600 F05

–100

–120

–2.5V

0

1

2

3

4

5

6

1MHz INPUT LEVEL (V

)

P-P

6600 F06

Figure 5. (S8 Pin Numbers)

Figure 6

Differential and Common Mode Voltage Ranges

V

can be shorted to V

for simplicity. If a different

OCM

MID

The differential ampliﬁers inside the LT6600-10 contain

circuitry to limit the maximum peak-to-peak differential

voltage through the ﬁlter. This limiting function prevents

excessive power dissipation in the internal circuitry

and provides output short-circuit protection. The limiting

function begins to take effect at output signal levels above

common mode output voltage is required, connect V

OCM

to a voltage source or resistor network. For 3V and 3.3V

supplies the voltage at V must be less than or equal to

themid-supplylevel. Forexample, voltage(V

OCM

) ≤1.65V

OCM

on a single 3.3V supply. For power supply voltages higher

than3.3VthevoltageatV canbesetabovemid-supply.

OCM

2V and it becomes noticeable above 3.5V . This is

P-P

The voltage on V

should not be more than 1V below

OCM

illustratedinFigure6;theLTC6600-10wasconﬁguredwith

unity passband gain and the input of the ﬁlter was driven

with a 1MHz signal. Because this voltage limiting takes

place well before the output stage of the ﬁlter reaches the

supply rails, the input/output behavior of the IC shown

in Figure 6 is relatively independent of the power supply

voltage.

the voltage on V . The voltage on V

should not be

MID OCM

MID

OCM

more than 2V above the voltage on V . V

is a high

impedance input.

The LT6600-10 was designed to process a variety of input

signals including signals centered around the mid-supply

voltage and signals that swing between ground and a

positive voltage in a single-supply system (Figure 1).

The range of allowable input common mode voltage (the

ThetwoampliﬁersinsidetheLT6600-10haveindependent

control of their output common mode voltage (see the

Block Diagram section). The following guidelines will

optimize the performance of the ﬁlter for single-supply

operation.

+

–

average of V and V

in Figure 1) is determined by

IN

the power supply level and gain setting (see the Electrical

Characteristics section).

V

must be bypassed to an AC ground with a 0.01μF or

Common Mode DC Currents

MID

highercapacitor.V canbedrivenfromalowimpedance

MID

In applications like Figure 1 and Figure 3 where the

LT6600-10notonlyprovideslowpassﬁlteringbutalsolevel

shifts the common mode voltage of the input signal, DC

66001fe

–

source, provided it remains at least 1.5V above V and at

+

least 1.5V below V . An internal resistor divider sets the

10

LT6600-10

APPLICATIONS INFORMATION

currents will be generated through the DC path between

input and output terminals. Minimize these currents to

decrease power dissipation and distortion.

Given the low noise output of the LT6600-10 and the 6dB

attenuation of the transformer coupling network, it will

be necessary to measure the noise ﬂoor of the spectrum

analyzer and subtract the instrument noise from the ﬁlter

noise measurement.

Consider the application in Figure 3. V

sets the output

MID

common mode voltage of the 1st differential ampliﬁer

inside the LT6600-10 (see the Block Diagram section) at

2.5V.Sincetheinputcommonmodevoltageisnear0V,there

willbeapproximatelyatotalof2.5V dropacrosstheseries

combinationoftheinternal402Ωfeedbackresistorandthe

external 100Ω input resistor. The resulting 5mA common

mode DC current in each input path, must be absorbed by

Example: With the IC removed and the 25Ω resistors

grounded, measure the total integrated noise (e ) of the

S

spectrum analyzer from 10kHz to 10MHz. With the IC

inserted, the signal source (V ) disconnected, and the

IN

input resistors grounded, measure the total integrated

noise out of the ﬁlter (e ). With the signal source

O

+

–

the sources V and V . V

sets the common mode

connected, set the frequency to 1MHz and adjust the

IN

OCM

output voltage of the 2nd differential ampliﬁer inside the

amplitude until V measures 100mV . Measure the

IN P-P

LT6600-10, and therefore sets the common mode output

output amplitude, V , and compute the passband gain

OUT

voltage of the ﬁlter. Since in the example, Figure 3, V

A = V /V . Now compute the input referred integrated

OCM

OUT IN

differs from V

by 0.5V, an additional 2.5mA (1.25mA

noise (e ) as:

IN

MID

per side) of DC current will ﬂow in the resistors coupling

the 1st differential ampliﬁer output stage to ﬁlter output.

Thus, a total of 12.5mA is used to translate the common

mode voltages.

(e_O)²–(e_S)²

e_IN=

A

Table 1 lists the typical input referred integrated noise for

A simple modiﬁcation to Figure 3 will reduce the DC

various values of R .

IN

common mode currents by 36ꢁ. If V

OCM

is shorted to

MID

Figure 8 is plot of the noise spectral density as a function

V

the common mode output voltage of both op amp

of frequency for an LT6600-10 with R = 402Ω using

stages will be 2V and the resulting DC current will be

8mA. Of course, by AC-coupling the inputs of Figure 3,

the common mode DC current can be reduced to 2.5mA.

IN

the ﬁxture of Figure 7 (the instrument noise has been

subtracted from the results).

Table 1. Noise Performance

INPUT REFERRED

Noise

PASSBAND

GAIN (V/V)

INTEGRATED NOISE

10kHz TO 10MHz

INPUT REFERRED

NOISE dBm/Hz

The noise performance of the LT6600-10 can be evaluated

with the circuit of Figure 7.

R

IN

4

2

1

100Ω

200Ω

402Ω

24ꢂV

34ꢂV

56ꢂV

–149

–146

–142

RMS

2.5V

0.1μF

SPECTRUM

COILCRAFT

ANALYZER

R

3

TTWB-1010

1:1

IN

V

IN

INPUT

1

7

2

8

The noise at each output is comprised of a differential

component and a common mode component. Using a

transformerorcombinertoconvertthedifferentialoutputs

tosingle-endedsignalrejectsthecommonmodenoiseand

gives a true measure of the S/N achievable in the system.

Conversely, if each output is measured individually and

the noise power added together, the resulting calculated

noise level will be higher than the true differential noise.

25Ω

–

4

+

LT6600-10

50Ω

–

5

+

25Ω

0.1μF

6

6600 F07

–2.5V

Figure 7. (S8 Pin Numbers)

66001fe

11

LT6600-10

APPLICATIONS INFORMATION

35

30

25

20

15

10

5

140

120

100

80

Junction temperature, T , is calculated from the ambient

J

temperature, T , and power dissipation, P . The power

A

D

dissipation is the product of supply voltage, V , and

S

supply current, I . Therefore, the junction temperature

S

is given by:

SPECTRAL DENSITY

60

T = T + (P • θ ) = T + (V • I • θ )

J

A

D

JA

A

S

JA

40

wherethesupplycurrent,I ,isafunctionofsignallevel,load

INTEGRATED

NOISE

S

impedance, temperature and common mode voltages.

20

0

For a given supply voltage, the worst-case power dis-

sipation occurs when the differential input signal is

maximum, the common mode currents are maximum

(seetheApplicationsInformationsectionregardingcom-

mon mode DC currents), the load impedance is small and

the ambient temperature is maximum. To compute the

junction temperature, measure the supply current under

these worst-case conditions, estimate the thermal resis-

tance from Table 2, then apply the equation for T_J. For

example, using the circuit in Figure 3 with DC differential

input voltage of 250mV, a differential output voltage of 1V,

no load resistance and an ambient temperature of 85°C,

the supply current (current into V⁺) measures 48.9mA.

Assuming a PC board layout with a 35mm²copper trace,

the θ_JAis 100°C/W. The resulting junction temperature is:

0.1

1.0

10

100

FREQUENCY (MHz)

6600 F08

Figure 8

Power Dissipation

The LT6600-10 ampliﬁers combine high speed with large-

signal currents in a small package. There is a need to

ensurethatthedies’sjunctiontemperaturedoesnotexceed

150°C. The LT6600-10 S8 package has Pin 6 fused to the

lead frame to enhance thermal conduction when connect-

ing to a ground plane or a large metal trace. Metal trace

and plated through-holes can be used to spread the heat

generated by the device to the backside of the PC board.

For example, on a 3/32" FR-4 board with 2oz copper, a

total of 660 square millimeters connected to Pin 6 of the

LT6600-10 S8 (330 square millimeters on each side of the

T = T + (P • θ ) = 85 + (5 • 0.0489 • 100) = 109°C

J

A

D

JA

When using higher supply voltages or when driving small

PC board) will result in a thermal resistance, θ ,of about

impedances, more copper may be necessary to keep T

below 150°C.

JA

J

85°C/W. Without the extra metal trace connected to the

–

V pin to provide a heat sink, the thermal resistance will

be around 105°C/W. Table 2 can be used as a guide when

considering thermal resistance.

Table 2. LT6600-10 SO-8 Package Thermal Resistance

COPPER AREA

TOPSIDE BACKSIDE BOARD AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

2

(mm )

1100

330

35

1100

330

35

0

2500

65°C/W

85°C/W

95°C/W

100°C/W

105°C/W

35

0

66001fe

12

LT6600-10

PACKAGE DESCRIPTION

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

DF Package

12-Lead Plastic DFN (4mm × 4mm)

(Reference LTC DWG # 05-08-1733 Rev Ø)

2.50 REF

0.70 0.05

3.38 0.05

4.50 0.05

2.65 0.05

3.10 0.05

PACKAGE OUTLINE

0.25 0.05

0.50 BSC

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

4.00 0.10

(4 SIDES)

2.50 REF

7

12

0.40 0.10

3.38 0.10

2.65 0.10

PIN 1 NOTCH

R = 0.20 TYP OR

0.35 × 45°

PIN 1

TOP MARK

(NOTE 6)

CHAMFER

(DF12) DFN 0806 REV Ø

6

R = 0.115

TYP

1

0.25 0.05

0.50 BSC

0.200 REF

0.75 0.05

BOTTOM VIEW—EXPOSED PAD

0.00 – 0.05

NOTE:

1. DRAWING IS PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220

VARIATION (WGGD-X)—TO BE APPROVED

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

66001fe

13

LT6600-10

PACKAGE DESCRIPTION

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

S8 Package

8-Lead Plastic Small Outline (Narrow .150 Inch)

(Reference LTC DWG # 05-08-1610)

.189 – .197

(4.801 – 5.004)

.045 .005

NOTE 3

.050 BSC

7

5

8

6

.245

MIN

.160 .005

.150 – .157

(3.810 – 3.988)

NOTE 3

.228 – .244

(5.791 – 6.197)

.030 .005

TYP

1

3

4

2

RECOMMENDED SOLDER PAD LAYOUT

.010 – .020

(0.254 – 0.508)

× 45°

.053 – .069

(1.346 – 1.752)

.004 – .010

(0.101 – 0.254)

.008 – .010

(0.203 – 0.254)

0°– 8° TYP

.016 – .050

(0.406 – 1.270)

.050

(1.270)

BSC

.014 – .019

(0.355 – 0.483)

TYP

NOTE:

INCHES

1. DIMENSIONS IN

(MILLIMETERS)

2. DRAWING NOT TO SCALE

3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)

SO8 0303

66001fe

14

LT6600-10

REVISION HISTORY ^{(Revision history begins at Rev D)}

REV

DATE

DESCRIPTION

PAGE NUMBER

D

5/10

Updated Order Information section

2

4

E

10/11 Corrected Conditions for Voltage at V

(Pin 7) and Power Supply Current

MID

66001fe

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

LT6600-10

TYPICAL APPLICATIONS

5th Order, 10MHz Lowpass Filter

(S8 Pin Numbers Shown)

Amplitude Response

Transient Response

5th Order, 10MHz Lowpass Filter

Differential Gain = 1

10

0

+

V

0.1μF

–10

–20

–30

–40

–50

–60

–70

–80

3

R

1

7

2

8

–

+

V

–

IN

4

+

–

+

V

+

OUT

LT6600-10

50mV/DIV

C

R

–

OUT

5

DIFFERENTIAL

INPUT

200mV/DIV

+

0.1μF

6

1

C =

2P • R • 10MHz

402Ω

DIFFERENTIAL GAIN = 1

R = 200Ω

6600 TA02a

–

6600 TA02c

GAIN =

, MAXIMUM GAIN = 4

V

100ns/DIV

C = 82pF

2R

100k

1M

10M

100M

FREQUENCY (Hz)

6600 TA02b

Amplitude Respo A WCDMA Transmit Filter

(10MHz Lowpass Filter with a 28MHz Notch, S8 Pin Numbers Shown)

Amplitude Response

22

+

33pF

V

0.1μF

12

2

3

1μH

100Ω

1

7

2

8

–

+

V

–

IN

4

–8

+

–

V

+

OUT

33pF

R

301Ω

Q

LT6600-10

–18

–28

–38

–48

–58

–68

–78

27pF

1μH

–

OUT

5

+

0.1μF

6

GAIN = 12dB

INDUCTORS ARE COILCRAFT 1008PS-102M

6600 TA03a

–

V

200k

1M

10M

100M

FREQUENCY (Hz)

6600 TA03b

RELATED PARTS

PART NUMBER

LTC^®1565-31

LTC1566-1

LT1567

DESCRIPTION

COMMENTS

650kHz Linear Phase Lowpass Filter

Low Noise, 2.3MHz Lowpass Filter

Continuous Time, SO8 Package, Fully Differential

Very Low Noise, High Frequency Filter Building Block

Very Low Noise, 4th Order Building Block

1.4nV/√Hz Op Amp, MSOP Package, Differential Output

LT1568

Lowpass and Bandpass Filter Designs Up to 10MHz, Differential Outputs

LTC6600-2.5

LTC6600-20

Very Low Noise, Differential Ampliﬁer and 2.5MHz

Lowpass Filter

Adjustable Output Common Mode Voltage

Very Low Noise, Differential Ampliﬁer and 20MHz

Lowpass Filter

Adjustable Output Common Mode Voltage

66001fe

LT 1011 REV E • 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：	LT6600CDF-10#TRPBF
厂家：	Linear
描述：	LT6600-10 - Very Low Noise, Differential Amplifier and 10MHz Lowpass Filter; Package: DFN; Pins: 12; Temperature Range: 0°C to 70°C 光电二极管
文件：	总16页 (文件大小：208K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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