LT6600CS8-2.5_技术文档

Final Electrical Specifications

LT6600-2.5

Very Low Noise, Differential

Amplifier and 2.5MHz Lowpass Filter

June 2003

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FEATURES

DESCRIPTIO

Programmable Differential Gain via Two External

The LT^®6600-2.5 combines a fully differential amplifier

with a 4th order 2.5MHz lowpass filter approximating a

Chebyshev frequency response. Most differential amplifi-

ers require many precision external components to tailor

gain and bandwidth. In contrast, with the LT6600-2.5, two

externalresistorsprogramdifferentialgain, andthefilter’s

2.5MHz cutoff frequency and passband ripple are inter-

nallyset.TheLT6600-2.5alsoprovidesthenecessarylevel

shifting to set its output common mode voltage to accom-

modate the reference voltage requirements of A/Ds.

■

Resistors

■

Adjustable Output Common Mode Voltage

■

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

■

0.5dB Ripple 4th Order Lowpass Filter with 2.5MHz

Cutoff

■

86dB S/N with 3V Supply and 1V_RMSOutput

■

Low Distortion, 1V_RMS, 800Ω Load

1MHz: 95dBc 2nd, 88dBc 3rd

■

Fully Differential Inputs and Outputs

■

Compatible with Popular Differential Amplifier

Using a proprietary internal architecture, the LT6600-2.5

integrates an antialiasing filter and a differential amplifier/

driver without compromising distortion or low noise

performance. At unity gain the measured in band

signal-to-noise ratio is an impressive 86dB. At higher

gains the input referred noise decreases so the part can

Pinouts

SO-8 Package

■

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APPLICATIO S

■

High Speed ADC Antialiasing and DAC Smoothing in

Networking or Cellular Base Station Applications

High Speed Test and Measurement Equipment

Medical Imaging

Drop-in Replacement for Differential Amplifiers

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

process smaller input differential signals without signifi-

cantly degrading the output signal-to-noise ratio.

■

The LT6600-2.5 also features low voltage operation. The

differential design provides outstanding performance for

a4V_P-Psignallevelwhilethepartoperateswithasingle3V

supply. The LT6600-2.5 is available in an SO-8 package.

For similar devices with higher cutoff frequency, refer to

the LT6600-10 and LT6600-20 data sheets.

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TYPICAL APPLICATIO

Amplitude Response

12

V

= ±2.5V

S

0

–12

–24

–36

–48

–60

–72

–84

–96

5V

0.1µF

1580Ω

3

1

7

2

8

–

+

V

–

IN

4

+

–

V

OUT

LT6600-2.5

0.01µF

1580Ω

V

OUT

5

+

6

660025 TA01a

100k

1M

10M

50M

FREQUENCY (Hz)

660025 TA01b

660025i

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 represen-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

1

LT6600-2.5

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ABSOLUTE AXI U RATI GS

(Note 1)

PACKAGE/ORDER I FOR ATIO

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

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

ORDER PART

TOP VIEW

NUMBER

–

+

IN

1

2

3

4

8

7

6

5

IN

V

LT6600CS8-2.5

LT6600IS8-2.5

OCM

MID

–

+

V

+

–

OUT

S8 PART MARKING

S8 PACKAGE

8-LEAD PLASTIC SO

660025

600I25

T_JMAX= 150°C, θ_JA= 100°C/W

Consult LTC Marketing for parts specified with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS

The ● denotes specifications that 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= 1580Ω, and R_LOAD= 1k.

PARAMETER

Filter Gain, V = 3V

CONDITIONS

MIN

– 0.5

– 0.15

– 0.2

– 0.6

–2.1

TYP

0.1

MAX

0.4

0.1

0.6

0.5

0

UNITS

dB

V

= 2V , f = DC to 260kHz

P-P IN

S

IN

R

= 1580Ω

= 2V , f = 700kHz (Gain Relative to 260kHz)

●

0

IN

P-P IN

= 2V , f = 1.9MHz (Gain Relative to 260kHz)

0.2

P-P IN

= 2V , f = 2.2MHz (Gain Relative to 260kHz)

0.1

P-P IN

= 2V , f = 2.5MHz (Gain Relative to 260kHz)

0.9

P-P IN

= 2V , f = 7.5MHz (Gain Relative to 260kHz)

– 34

– 51

–0.1

0

– 31

P-P IN

= 2V , f = 12.5MHz (Gain Relative to 260kHz)

P-P IN

Filter Gain, V = 5V

= 2V , f = DC to 260kHz

–0.5

– 0.15

– 0.2

– 0.6

– 2.1

0.4

0.1

0.6

0.5

0

S

P-P IN

R

= 1580Ω

= 2V , f = 700kHz (Gain Relative to 260kHz)

●

IN

P-P IN

= 2V , f = 1.9MHz (Gain Relative to 260kHz)

0.2

P-P IN

= 2V , f = 2.2MHz (Gain Relative to 260kHz)

0.1

P-P IN

= 2V , f = 2.5MHz (Gain Relative to 260kHz)

–0.9

–34

–51

–0.1

P-P IN

= 2V , f = 7.5MHz (Gain Relative to 260kHz)

–31

P-P IN

= 2V , f = 12.5MHz (Gain Relative to 260kHz)

P-P IN

Filter Gain, V = ±5V

= 2V , f = DC to 260kHz

–0.6

0.4

S

P-P IN

Filter Gain, R = 402Ω

V

= 2V , f = DC to 260kHz, V = 3V

11.3

11.2

11.8

11.7

12.3

12.2

dB

IN

P-P IN

S

= 2V , f = DC to 260kHz, V = 5V

P-P IN

S

= 2V , f = DC to 260kHz, V = ±5V

P-P IN

S

Filter Gain Temperature Coefficient (Note 2)

f

= 260kHz, V = 2V

P-P

780

51

ppm/C

IN

Noise

Noise BW = 10kHz to 2.5MHz

1MHz, 1V , R = 800Ω

µV

RMS

Distortion (Note 4)

2nd Harmonic

3rd Harmonic

95

88

dBc

RMS

L

Differential Output Swing

Input Bias Current

Measured Between Pins 4 and 5

Average of Pin 1 and Pin 8

V = 5V

S

●

8.8

5.1

9.3

5.5

V

S

P-P DIFF

V = 3V

●

– 35

–15

µA

660025i

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LT6600-2.5

ELECTRICAL CHARACTERISTICS

The ● denotes specifications that 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= 1580Ω, and R_LOAD= 1k.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Input Referred Differential Offset

R

IN

= 1580Ω

V = 3V

●

5

25

30

35

mV

S

V = 5V

S

V = ±5V

S

R

IN

= 402Ω

V = 3V

●

3

13

16

20

mV

S

V = 5V

S

V = ±5V

S

Differential Offset Drift

10

µV/°C

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

= 402Ω

V = 5V

S

V = ±5V

S

Output Common Mode Voltage (Note 5)

Differential Input = 2V

Pin 7 at Mid-Supply

,

V = 3V

●

1.0

1.5

–1.0

1.5

3.0

2.0

V

P-P

S

V = 5V

S

V = ±5V

S

Output Common Mode Offset

(with Respect to Pin 2)

V = 3V

●

–25

–30

–55

10

5

–10

45

35

mV

S

V = 5V

S

V = ±5V

S

Common Mode Rejection Ratio

63

dB

Voltage at V

(Pin 7)

V = 5V

S

●

2.46

4.3

2.51

1.5

2.55

7.7

V

MID

S

V = 3V

V

Input Resistance

Bias Current

5.7

kΩ

MID

V

= V = V /2

V = 5V

●

–15

–10

–3

µA

OCM

MID

S

V = 3V

S

Power Supply Current

V = 3V, V = 5V

26

30

33

36

mA

S

V = 3V, V = 5V

●

S

V = ±5V

28

S

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

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

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 Pin 2.

resistors assuming a temperature independent external resistor (R ).

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

Note 6: Both the LT6600CS8-2.5 and LT6600IS8-2.5 are guaranteed

functional over the operating temperature range of –40°C to 85°C.

IN

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

Note 7: The LT6600CS8-2.5 is guaranteed to meet specified performance

from 0°C to 70°C and is designed, characterized and expected to meet

specified performance from –40°C and 85°C, but is not tested or QA

sampled at these temperatures. The LT6600IS8-2.5 is guaranteed to meet

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

IN

R

IN

≥ 402Ω.

Note 4: Distortion is measured differentially using a single-ended

stimulus. The input common mode voltage, the voltage at Pin 2, and the

voltage at Pin 7 are equal to one half of the total power supply voltage.

660025i

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LT6600-2.5

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PI FU CTIO S

IN^–and IN⁺(Pins 1, 8): Input Pins. Signals can be applied

to either or both input pins through identical external

resistors, R_IN. The DC gain from differential inputs to the

differential outputs is 1580Ω/R_IN.

supply applications, bypass Pin 3 to ground and Pin 6 to

ground with a quality 0.1µF ceramic capacitor.

OUT⁺and OUT^–(Pins 4, 5): Output Pins. Pins 4 and 5 are

the filter differential outputs. Each pin can drive a 100Ω

and/or 50pF load to AC ground.

V

_OCM(Pin 2): Is the DC Common Mode Reference Voltage

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

mode voltage of the differential output of the filter. Pin 2 is

a high impedance input, which can be driven from an

external voltage reference, or Pin 2 can be tied to Pin 7 on

the PC board. Pin 2 should be bypassed with a 0.01µF

ceramiccapacitorunlessitisconnectedtoagroundplane.

V⁺and V^–(Pins 3, 6): Power Supply Pins. For a single

3.3V or 5V supply (Pin 6 grounded) a quality 0.1µF

ceramic bypass capacitor is required from the positive

supply pin (Pin 3) to the negative supply pin (Pin 6). The

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

V

_MID(Pin 7): The V_MIDpin is internally biased at mid-

supply, see block diagram. For single supply operation,

the V_MIDpin should be bypassed with a quality 0.01µF

ceramic capacitor to Pin 6. For dual supply operation, Pin

7 can be bypassed or connected to a high quality DC

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

will increase noise and distortion. Pin 7 sets the output

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.

660025i

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LT6600-2.5

W

BLOCK DIAGRA

R

IN

+

–

V

IN

V

OUT

5

V

MID

8

7

6

+

V

11k

PROPRIETARY

LOWPASS

FILTER STAGE

1580Ω

800Ω

–

V

OP AMP

800Ω

+

OCM

–

V

OCM

+

–

800Ω

1580Ω

1

2

3

4

660025 BD

+

–

+

V

IN

OCM

V

OUT

R

IN

660025i

5

LT6600-2.5

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APPLICATIO S I FOR ATIO

Interfacing to the LT6600-2.5

output voltage is 1.65V, and the differential output voltage

is 2V_P-Pfor frequencies below 2.5MHz. The common

mode output voltage is determined by the voltage at pin 2.

Since pin 2 is shorted to pin 7, the output common mode

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

input voltage can be equal to the mid-supply voltage of

Pin 7.

TheLT6600-2.5requirestwoequalexternalresistors,R_IN,

to set the differential gain to 1580Ω/R_IN. The inputs to the

+

filter are the voltages V_INand V_IN^–presented to these

external components, Figure 1. The difference between

V_IN⁺and V_IN^–is the differential input voltage. The average

+

–

of V_INand V_INis the common mode input voltage.

Similarly, the voltages V_OUT⁺and V_OUT^–appearing at Pins

4 and 5 of the LT6600-2.5 are the filter outputs. The

Figure 2 shows how to AC couple signals into the

LT6600-2.5. In this instance, the input is a single-ended

signal. AC coupling allows the processing of single-ended

or differential signals with arbitrary common mode levels.

The 0.1µF coupling capacitor and the 1580Ω gain setting

resistor form a high pass filter, attenuating signals below

1kHz. Larger values of coupling capacitors will propor-

tionally reduce this highpass 3dB frequency.

+

–

+

difference between V_OUTand V_OUTis the differential

–

output voltage. The average of V_OUTand V_OUTis the

common mode output voltage.

Figure 1 illustrates the LT6600-2.5 operating with a single

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

DCcoupled. Thecommonmodeinputvoltageis0.5V, and

the differential input voltage is 2V_P-P. The common mode

3.3V

0.1µF

V

3

–

1580Ω

3

2

1

0

3

2

1

0

1

7

2

8

–

V

4

IN

+

–

+

–

V

+

V

OUT

LT6600-2.5

+

V

0.01µF

1580Ω

IN

V

OUT

–

+

OUT

5

+

6

t

–

660025 F01

V

IN

Figure 1

3.3V

3

0.1µF

V

0.1µF

1580Ω

1

7

2

3

2

1

0

2

1

–

4

+

–

V

+

OUT

V

OUT

LT6600-2.5

+

V

IN

0.01µF

–

OUT

–

0

t

8

OUT

+

5

V

IN

+

6

–1

660025 F02

Figure 2

5V

0.1µF

V

3

402Ω

1

–

+

3

V

–

4

IN

+

–

V

OUT

+

7

OUT

LT6600-2.5

2

1

0

2

1

2

8

V

OUT

0.01µF

402Ω

–

V

500mV (DIFF)

P-P

–

OUT

5

V

IN

+

V

IN

6

t

0

–

+

660025 F03

2V

IN

–

Figure 3

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LT6600-2.5

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APPLICATIO S I FOR ATIO

In Figure 3 the LT6600-2.5 is providing 12dB of gain. The

common mode output voltage is set to 2V.

Figure 5 is a laboratory setup that can be used to charac-

terize the LT6600-2.5 using single-ended instruments

with 50Ω source impedance and 50Ω input impedance.

For a 12dB gain configuration the LT6600-2.5 requires a

402Ωsourceresistanceyetthenetworkanalyzeroutputis

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 of the

LT6600-2.5 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 Figure 5, present the output of the LT6600-2.5

with a 1600Ω 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 between the transformer and analyzer input.

Use Figure 4 to determine the interface between the

LT6600-2.5 and a current output DAC. The gain, or “trans-

impedance,” is defined as A = V_OUT/I_IN. To compute the

transimpedance, use the following equation:

1580 •R1

A =

Ω

( )

R1+R2

(

)

By setting R1 + R2 = 1580Ω, the gain equation reduces to

A = R1(Ω).

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

R2, the voltage on Pin 7 and the DAC output current.

Consider Figure 4 with R1 = 49.9Ω and R2 = 1540Ω. The

voltage at Pin 7 is 1.65V. The voltage at the DAC pins is

given by:

Differential and Common Mode Voltage Ranges

R1

R1•R2

R1+R2

V

_DAC= V_PIN7

•

+I •

IN

Therail-to-railoutputstageoftheLT6600-2.5canprocess

large differential signal levels. On a 3V supply, the output

signal can be 5.1V_P-P. Similarly, a 5V supply can support

signals as large as 8.8V_P-P. To prevent excessive power

dissipation in the internal circuitry, the user must limit

R1+R2 +1580

= 26mV +I • 48.3Ω

IN

I_INis I_IN⁺or I_IN^–. The transimpedance in this example is

49.6Ω.

differential signal levels to 9V_P-P

.

Evaluating the LT6600-2.5

The two amplifiers inside the LT6600-2.5 have indepen-

dent control of their output common mode voltage (see

the “Block Diagram” section). The following guidelines

will optimize the performance of the filter.

The low impedance levels and high frequency operation of

the LT6600-2.5 require some attention to the matching

networks between the LT6600-2.5 and other devices. The

previous examples assume an ideal (0Ω) source imped-

ance and a large (1kΩ) load resistance. Among practical

examples where impedance must be considered is the

evaluation of the LT6600-2.5 with a network analyzer.

Pin 7 can be allowed to float; Pin 7 must be bypassed to an

ACgroundwitha0.01µFcapacitororsomeinstabilitymay

be observed. Pin 7 can be driven from a low impedance

2.5V

0.1µF

CURRENT

OUTPUT

DAC

3.3V

COILCRAFT

TTWB-16A

4:1

COILCRAFT

TTWB-1010

NETWORK

ANALYZER

SOURCE

NETWORK

ANALYZER

INPUT

0.1µF

3

388Ω

1:1

1

7

2

8

402Ω

–

4

–

+

3

R2

I

IN

1

7

2

8

50Ω

LT6600-2.5

–

4

+

–

53.6Ω

50Ω

V

+

OUT

R1

+

–

0.01µF

LT6600-2.5

5

+

402Ω

388Ω

–

6

IN

OUT

0.1µF

5

+

660025 F05

6

R1

660025 F04

–2.5V

Figure 5

Figure 4

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LT6600-2.5

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APPLICATIO S I FOR ATIO

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

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

voltage of Pin 7. While the internal 11k resistors are well

matched, their absolute value can vary by ±20%. This

should be taken into consideration when connecting an

external resistor network to alter the voltage of Pin 7.

amplifier inside the LT6600-2.5, and therefore sets the

common mode output voltage of the filter. Since, in the

example of Figure 3, Pin 2 differs from Pin 7 by 0.5V, an

additional 625µA (312µA per side) of DC current will flow

in the resistors coupling the 1st differential amplifier

output stage to filter output. Thus, a total of 3.125mA is

used to translate the common mode voltages.

Pin 2 can be shorted to Pin 7 for simplicity. If a different

common mode output voltage is required, connect Pin 2

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

supplies the voltage at Pin 2 must be less than or equal to

the mid supply level. For example, voltage (Pin 2) ≤ 1.65V

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

than 3.3V the voltage at Pin 2 can be set above mid supply.

The voltage on Pin 2 should not exceed 1V below the

voltage on Pin 7. The voltage on Pin 2 should not be more

than 2V above the voltage on Pin 7. Pin 2 is a high

impedance input.

A simple modification to Figure 3 will reduce the DC

common mode currents by 36%. If Pin 7 is shorted to

Pin 2 the common mode output voltage of both op amp

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

Of course, by AC coupling the inputs of Figure 3, the

common mode DC current can be reduced to 625µA.

Noise

The noise performance of the LT6600-2.5 can be evalu-

ated with the circuit of Figure 6.

TheLT6600-2.5wasdesignedtoprocessavarietyofinput

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

average of V_INand V_INin Figure 1) is determined by

the power supply level and gain setting (see “Electrical

Characteristics”).

Given the low noise output of the LT6600-2.5 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.

+

–

Example: With the IC removed and the 25Ω resistors

grounded, Figure 6, measure the total integrated noise

(e_S) of the spectrum analyzer from 10kHz to 2.5MHz. With

the IC inserted, the signal source (V_IN) disconnected, and

the input resistors grounded, measure the total integrated

noise out of the filter (e_O). With the signal source con-

nected, set the frequency to 100kHz and adjust the ampli-

tude until V_INmeasures 100mV_P-P. Measure the output

amplitude, V_OUT, and compute the passband gain

Common Mode DC Currents

In applications like Figure 1 and Figure 3 where the

LT6600-2.5 not only provides lowpass filtering but also

level shifts the common mode voltage of the input signal,

DC currents will be generated through the DC path be-

tweeninputandoutputterminals.Minimizethesecurrents

to decrease power dissipation and distortion.

2.5V

0.1µF

Consider the application in Figure 3. Pin 7 sets the output

common mode voltage of the 1st differential amplifier

inside the LT6600-2.5 (see the “Block Diagram” section)

at 2.5V. Since the input common mode voltage is near 0V,

there will be approximately a total of 2.5V drop across the

series combination of the internal 1580Ω feedback resis-

tor and the external 402Ω input resistor. The resulting

1.25mA common mode DC current in each input path,

must be absorbed by the sources V_IN⁺and V_IN^–. Pin 2 sets

the common mode output voltage of the 2nd differential

SPECTRUM

COILCRAFT

ANALYZER

R

3

TTWB-1010

1:1

IN

V

IN

INPUT

1

7

2

8

25Ω

–

4

+

LT6600-2.5

50Ω

–

5

+

25Ω

0.1µF

6

66002 F06

–2.5V

Figure 6

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LT6600-2.5

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APPLICATIO S I FOR ATIO

50

40

30

20

10

0

100

80

A = V_OUT/V_IN. Now compute the input referred integrated

noise (e_IN) as:

SPECTRAL DENSITY

(e_O)²–(e_S)²

60

e_IN=

A

40

Table 1 lists the typical input referred integrated noise for

various values of R_IN.

20

INTEGRATED

Figure 7 is plot of the noise spectral density as a function

of frequency for an LT6600-2.5 with R_IN= 1580Ω using

the fixture of Figure 6 (the instrument noise has been

subtracted from the results).

0

0.01

0.1

1

10

FREQUENCY (MHz)

66002 F07

Figure 7. Input Referred Noise, Gain = 1

Table 1. Noise Performance

INPUT REFERRED

INTEGRATED NOISE INTEGRATED NOISE

10kHz TO 2.5MHz 10kHz TO 5MHz

INPUT REFERRED

Table 2. LT6600-2.5 SO-8 Package Thermal Resistance

COPPER AREA

PASSBAND

GAIN (V/V)

R

IN

TOPSIDE BACKSIDE BOARD AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

4

2

1

402Ω

806Ω

18µV

29µV

51µV

23µV

39µV

73µV

RMS

2

(mm )

1100

330

35

1100

330

35

2500

65°C/W

1580Ω

85°C/W

95°C/W

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,ifeachoutputismeasuredindividuallyandthe

noisepoweraddedtogether,theresultingcalculatednoise

level will be higher than the true differential noise.

35

0

100°C/W

0

105°C/W

about 85°C/W. Without 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.

Junction temperature, T_J, is calculated from the ambient

temperature, T_A, and power dissipation, P_D. The power

dissipation is the product of supply voltage, V_S, and

supply current, I_S. Therefore, the junction temperature is

given by:

Power Dissipation

TheLT6600-2.5amplifierscombinehighspeedwithlarge-

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

ensure that the dies’s junction temperature does not

exceed150°C. TheLT6600-2.5packagehasPin6fusedto

the lead frame to enhance thermal conduction when

connecting 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 LT6600-2.5 (330 square millimeters on each side

of the PC board) will result in a thermal resistance, θ_JA, of

T_J= T_A+ (P_D• θ_JA) = T_A+ (V_S• I_S• θ_JA)

where the supply current, I_S, is a function of signal level,

load impedance, temperature and common mode

voltages.

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

pation occurs when the differential input signal is maxi-

mum, the common mode currents are maximum (see

Applications Information regarding Common Mode DC

660025i

9

LT6600-2.5

U

W U U

APPLICATIO S I FOR ATIO

Currents), the load impedance is small and the ambient

temperature is maximum. To compute the junction tem-

perature, measure the supply current under these worst-

case conditions, estimate the thermal resistance from

Table2, thenapplytheequationforT_J. Forexample, using

the circuit in Figure 3 with DC differential input voltage of

1V, a differential output voltage of 4V, no load resistance

and an ambient temperature of 85°C, the supply current

(current into Pin 3) measures 37.6mA. Assuming a PC

board layout with a 35mm²copper trace, the θ_JAis

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

T_J= T_A+ (P_D• θ_JA) = 85 + (5 • 0.0376 • 100) = 104°C

When using higher supply voltages or when driving small

impedances, more copper may be necessary to keep T_J

below 150°C.

660025i

10

LT6600-2.5

U

PACKAGE DESCRIPTIO

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

660025i

11

LT6600-2.5

RELATED PARTS

PART NUMBER

LTC^®1565-31

LTC1566-1

LT1567

DESCRIPTION

COMMENTS

650kHz Linear Phase Lowpass Filter

Continuous Time, SO8 Package, Fully Differential

Continuous Time, SO8 Package

Low Noise, 2.3MHz Lowpass Filter

Very Low Noise, High Frequency Filter Building Block

Very Low Noise, 4th Order Building Block

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

LT1568

Lowpass and Bandpass Filter Designs Up to 10MHz,

Differential Outputs

LT6600-10

LT6600-20

Very Low Noise Differential Amplifier and 10MHz

Lowpass Filter

82dB S/N with 3V Supply, SO-8 Package

Very Low Noise Differential Amplifier and 20MHz

Lowpass Filter

76dB S/N with 3V Supply, SO-8 Package

660025i

LT/TP 0603 1K • PRINTED IN USA

12 ^{LinearTechnology Corporation}

1630 McCarthy Blvd., Milpitas, CA 95035-7417

●

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

LINEAR TECHNOLOGY CORPORATION 2003


型号：	LT6600CS8-2.5
厂家：	Linear
描述：	Very Low Noise, Differential Amplifier and 2.5MHz Lowpass Filter 非常低噪声，差分放大器和2.5MHz的低通滤波器运算放大器放大器电路
文件：	总12页 (文件大小：169K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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