LTC6401CUD-26-PBF [Linear]
1.6GHz Low Noise, Low Distortion Differential ADC Driver for DC-140MHz; 1.6GHz的低噪声,低失真差分ADC驱动器为DC- 140MHz的型号: | LTC6401CUD-26-PBF |
厂家: | Linear |
描述: | 1.6GHz Low Noise, Low Distortion Differential ADC Driver for DC-140MHz |
文件: | 总16页 (文件大小:224K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC6401-26
1.6GHz Low Noise,
Low Distortion Differential
ADC Driver for DC-140MHz
FEATURES
DESCRIPTION
The LTC®6401-26 is a high-speed differential amplifier
targeted at processing signals from DC to 140MHz. The
part has been specifically designed to drive 12-, 14- and
16-bitADCswithlownoiseandlowdistortion,butcanalso
be used as a general-purpose broadband gain block.
■
1.6GHz –3dB Bandwidth
■
Fixed Gain of 20V/V (26dB)
■
–85dBc IMD3 at 70MHz (Equivalent OIP3 = 46.5dBm)
■
–72dBc IMD3 at 140MHz (Equivalent OIP3 = 40dBm)
■
1nV/√Hz Internal Op Amp Noise
■
1.5nV/√Hz Total Input Referred Noise
The LTC6401-26 is easy to use, with minimal support
circuitry required. The output common mode voltage is
set using an external pin, independent of the inputs, which
eliminates the need of transformers or AC-coupling ca-
pacitors in many applications. The gain is internally fixed
at 26dB (20V/V).
■
6.8dB Noise Figure
■
Differential Inputs and Outputs
■
50Ω Input Impedance
■
2.85V to 3.5V Supply Voltage
■
45mA Supply Current (135mW)
■
1V to 1.6V Output Common Mode, Adjustable
■
The LTC6401-26 saves space and power compared to
alternative solutions using IF gain blocks and transform-
ers. The LTC6401-26 is packaged in a compact 16-lead
3mm × 3mm QFN package and operates over the –40°C
to 85°C temperature range.
DC- or AC-Coupled Operation
Max Differential Output Swing 4.7V
■
P-P
■
Small 16-Lead 3mm × 3mm × 0.75mm QFN Package
APPLICATIONS
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
■
Differential ADC Driver
■
Differential Driver/Receiver
■
Single Ended to Differential Conversion
IF Sampling Receivers
SAW Filter Interfacing
■
■
TYPICAL APPLICATION
Equivalent OIP3 vs Frequency
Single-Ended to Differential ADC Driver at 140MHz IF
60
3.3V
3.3V
DIFFERENTIAL INPUT
(NOTE 7)
50
0.1μF
1000pF
33pF
40
30
+
V
0.1μF
0.1μF
15Ω
15Ω
10Ω
10Ω
V
DD
+
–
+OUT
AIN
V
+IN
IN
L1
24nH
150Ω
20
10
0
LTC6401-26
33pF
33pF
LTC2208
–IN
–OUT
AIN
V
CM
V
NO R
L
OCM
37.4Ω
–
COILCRAFT
0603CS
R
L
= 200Ω
LTC2208
130Msps
16-BIT ADC
V
0
50
100
150
200
1.25V
640126 TA01a
FREQUENCY (MHz)
100Ω
640126 TA01b
0.1μF
640126f
1
LTC6401-26
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
+
–
Supply Voltage (V – V )..........................................3.6V
Input Current (Note 2).......................................... 10mA
Operating Temperature Range
16 15 14 13
+
–
V
1
2
3
4
12 V
(Note 3) ............................................... –40°C to 85°C
Specified Temperature Range
(Note 4) ............................................... –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
Maximum Junction Temperature .......................... 150°C
V
11 ENABLE
+
OCM
+
17
V
V
V
10
9
–
–
V
5
6
7
8
UD PACKAGE
16-LEAD (3mm × 3mm) PLASTIC QFN
= 150°C, θ = 68°C/W, θ = 4.2°C/W
T
JMAX
JA
JC
–
EXPOSED PAD (PIN 17) IS V , MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC6401CUD-26#PBF
LTC6401IUD-26#PBF
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
SPECIFIED TEMPERATURE RANGE
LTC6401CUD-26#TRPBF LCDG
LTC6401IUD-26#TRPBF LCDG
16-Lead (3mm × 3mm) Plastic QFN
16-Lead (3mm × 3mm) Plastic QFN
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
LTC6400 AND LTC6401 SELECTOR GUIDE Please check each datasheet for complete details.
PART NUMBER
GAIN
(dB)
GAIN
(V/V)
Z
IN
(DIFFERENTIAL)
I
CC
(mA)
(Ω)
LTC6401-8
LTC6401-20
LTC6401-26
LTC6400-20
LTC6400-26
8
2.5
10
20
10
20
400
200
50
45
20
26
20
26
50
45
200
50
90
85
In addition to the LTC6401 family of amplifiers, a lower distortion LTC6400 family is available. The LTC6400 is pin compatible to the LTC6401, and has the
same low noise performance. The low distortion of the LTC6400 comes at the expense of higher power consumption. Please refer to the separate LTC6400
data sheets for complete details. Other gain versions from 8dB to 14dB will follow.
640126f
2
LTC6401-26
DC ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. V+ = 3V, V– = 0V, +IN = –IN = VOCM = 1.25V, ENABLE = 0V, No RL unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input/Output Characteristic (+IN, –IN, +OUT, –OUT, +OUTF, –OUTF)
●
●
●
●
●
●
G
Gain
V
V
=
=
50mV Differential
50mV Differential
25
26
0.003
0.09
2.43
4.7
27
dB
dB/°C
V
DIFF
IN
TC
Gain Temperature Drift
Output Swing Low
Output Swing High
Maximum Differential Output Swing
Output Current Drive
GAIN
IN
V
V
V
Each Output, V
Each Output, V
=
=
200mV Differential
200mV Differential
0.15
SWINGMIN
SWINGMAX
OUTDIFFMAX
OUT
IN
IN
2.3
4.3
10
V
1dB Compressed
Each Output, V
V
P-P
I
=
200mV,
mA
IN
V
OUT
> 2V
P-P
●
●
V
Input Offset Voltage
Differential
Differential
–2.5
2.5
1
mV
μV/°C
V
OS
TCV
Input Offset Voltage Drift
1
OS
VRMIN
VRMAX
I
I
Input Common Mode Voltage Range, MIN
Input Common Mode Voltage Range, MAX
Input Resistance (+IN, –IN)
1.6
V
●
Ω
R
Differential
42.5
50
1
57.5
INDIFF
INDIFF
C
Input Capacitance (+IN, –IN)
Differential, Includes Parasitic
Differential
pF
●
●
Ω
R
R
Output Resistance (+OUT, –OUT)
Filtered Output Resistance (+OUTF, –OUTF)
18
85
25
100
2.7
75
32
OUTDIFF
OUTFDIFF
OUTFDIFF
Ω
Differential
115
C
Filtered Output Capacitance (+OUTF, –OUTF) Differential, Includes Parasitic
pF
●
CMRR
Common Mode Rejection Ratio
Input Common Mode Voltage
1.1V to1.4V
50
dB
Output Common Mode Control
G
Common Mode Gain
V
= 1V to 1.6V
1
V/V
CM
OCM
OCM
V
V
V
Output Common Mode Range, MIN
1
V
V
OCMMIN
●
1.1
Output Common Mode Range, MAX
1.6
1.5
V
V
OCMMAX
●
●
●
●
Common Mode Offset Voltage
V
= 1.1V to 1.5V
–15
15
15
mV
μV/°C
μA
OSCM
TCV
Common Mode Offset Voltage Drift
3
5
OSCM
IV
V
Input Current
OCM
OCM
ENABLE Pin
●
●
●
●
V
V
ENABLE Input Low Voltage
ENABLE Input High Voltage
ENABLE Input Low Current
ENABLE Input High Current
0.8
V
V
IL
2.4
IH
I
IL
I
IH
ENABLE = 0.8V
ENABLE = 2.4V
0.5
3
μA
μA
1.4
Power Supply
●
●
V
Operating Supply Range
Supply Current
2.85
35
3
3.5
60
V
S
I
S
ENABLE = 0V, Both Inputs and
Outputs Floating
45
mA
●
●
I
Shutdown Supply Current
ENABLE = 3V, Both Inputs and
Outputs Floating
0.8
3
mA
dB
SHDN
PSRR
Power Supply Rejection Ratio (Differential
Outputs)
2.85V to 3.5V
60
95.5
640126f
3
LTC6401-26
AC ELECTRICAL CHARACTERISTICS Specifications are at TA = 25°C. V+ = 3V, V– = 0V, VOCM = 1.25V,
ENABLE = 0V, No RL unless otherwise noted.
SYMBOL
–3dBBW
0.5dBBW
0.1dBBW
1/f
PARAMETER
CONDITIONS
MIN
TYP
1.6
0.5
0.22
16
MAX
UNITS
GHz
GHz
GHz
kHz
V/μs
ns
–3dB Bandwidth
200mV
200mV
200mV
(Note 6)
(Note 6)
(Note 6)
1.2
P-P,OUT
P-P,OUT
P-P,OUT
Bandwidth for 0.5dB Flatness
Bandwidth for 0.1dB Flatness
1/f Noise Corner
SR
Slew Rate
Differential V
= 2V Step (Note 6)
3300
3
OUT
t
t
t
t
1% Settling Time
Overdrive Recovery Time
Turn-On Time
V
OUT
V
OUT
= 2V (Note 6)
P-P
S1%
OVDR
ON
= 1.9V (Note 6)
19
ns
P-P
+OUT, –OUT Within 10% of Final Values
Falls to 10% of Nominal
93
ns
Turn-Off Time
I
140
14.7
ns
OFF
CC
–3dBBW
V
Pin Small Signal –3dB BW
0.1V at V , Measured Single-Ended
OCM
MHz
VOCM
OCM
P-P
at Output (Note 6)
10MHz Input Signal
HD2,10M/HD3,10M Second/Third Order Harmonic Distortion
V
OUT
V
OUT
V
OUT
V
OUT
V
OUT
= 2V , R = 200Ω
–95/–81
–93/–96
–80
dBc
dBc
dBc
dBc
dBm
P-P
L
= 2V , No R
P-P
L
IMD3,10M
OIP3,10M
Third-Order Intermodulation
(f1 = 9.5MHz f2 = 10.5MHz)
= 2V Composite, R = 200Ω
P-P L
= 2V Composite, No R
–97
P-P
L
Equivalent Third-Order Output Intercept
Point (f1 = 9.5MHz f2 = 10.5MHz)
= 2V Composite, No R (Note 7)
52.5
P-P
L
P
1dB Compression Point
R = 375Ω (Notes 5, 7)
17.3
6.8
1.5
30
dBm
dB
1dB,10M
L
NF
Noise Figure
R = 375Ω (Note 5)
L
10M
e
e
Input Referred Voltage Noise Density
Output Referred Voltage Noise Density
Includes Resistors (Short Inputs)
Includes Resistors (Short Inputs)
nV/√Hz
nV/√Hz
IN,10M
ON,10M
70MHz Input Signal
HD2,70M/HD3,70M Second/Third Order Harmonic Distortion
V
OUT
V
OUT
V
OUT
V
OUT
V
OUT
= 2V , R = 200Ω
–83/–66
–86/–81
–74
dBc
dBc
dBc
dBc
dBm
P-P
L
= 2V , No R
P-P
L
IMD3,70M
OIP3,70M
Third-Order Intermodulation
(f1 = 69.5MHz f2 = 70.5MHz)
= 2V Composite, R = 200Ω
P-P L
= 2V Composite, No R
–85
P-P
L
Equivalent Third-Order Output Intercept
Point (f1 = 69.5MHz f2 = 70.5MHz)
= 2V Composite, No R (Note 7)
46.5
P-P
L
P
1dB Compression Point
R = 375Ω (Notes 5, 7)
17.2
6.7
dBm
dB
1dB,70M
L
NF
Noise Figure
R = 375Ω (Note 5)
L
70M
e
e
Input Referred Voltage Noise Density
Output Referred Voltage Noise Density
Includes Resistors (Short Inputs)
Includes Resistors (Short Inputs)
1.44
28.8
nV/√Hz
nV/√Hz
IN,70M
ON,70M
640126f
4
LTC6401-26
AC ELECTRICAL CHARACTERISTICS Specifications are at TA = 25°C. V+ = 3V, V– = 0V, VOCM = 1.25V,
ENABLE = 0V, No RL unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
140MHz Input Signal
HD2,140M/
HD3,140M
Second/Third Order Harmonic Distortion
V
OUT
V
OUT
V
OUT
V
OUT
V
OUT
= 2V , R = 200Ω
–81/–54
–85/–69
–64
dBc
dBc
dBc
dBc
dBm
P-P
L
= 2V , No R
P-P
L
IMD3,140M
Third-Order Intermodulation
(f1 = 139.5MHz f2 = 140.5MHz)
= 2V Composite, R = 200Ω
P-P L
= 2V Composite, No R
–72
P-P
L
OIP3,140M
Equivalent Third-Order Output Intercept
Point(f1 = 139.5MHz f2 = 140.5MHz)
= 2V Composite, No R (Note 7)
40
P-P
L
P
1dB Compression Point
R = 375Ω (Notes 5, 7)
17.4
6.5
dBm
dB
1dB,140M
L
NF
Noise Figure
R = 375Ω (Note 5)
L
140M
N,140M
ON,140M
e
e
Input Referred Voltage Noise Density
Output Referred Voltage Noise Density
Includes Resistors (Short Inputs)
Includes Resistors (Short Inputs)
1.43
28.6
–70
nV/√Hz
nV/√Hz
dBc
IMD
Third-Order Intermodulation
(f1 = 130MHz f2 = 150MHz)
Measure at 170MHz
V
= 2V Composite, R = 375Ω
–62
3,130M/150M
OUT
P-P
L
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: Input pins (+IN, –IN) are protected by steering diodes to either
supply. If the inputs go beyond either supply rail, the input current should
be limited to less than 10mA.
temperatures. The LTC6401I is guaranteed to meet specified performance
from –40°C to 85°C.
Note 5: Input and output baluns used. See Test Circuit A.
Note 6: Measured using Test Circuit B. R = 87.5Ω per output.
L
Note 7: Since the LTC6401-26 is a feedback amplifier with low output
impedance, a resistive load is not required when driving an AD converter.
Therefore, typical output power is very small. In order to compare the
LTC6401-26 with amplifiers that require 50Ω output load, the output
Note 3: The LTC6401C and LTC6401I are guaranteed functional over the
operating temperature range of –40°C to 85°C
voltage swing driving a given R is converted to OIP and P as if it were
L
3
1dB
Note 4: The LTC6401C is guaranteed to meet specified performance from
0°C to 70°C. It is designed, characterized and expected to meet specified
performance from –40°C to 85°C but is not tested or QA sampled at these
driving a 50Ω load. Using this modified convention, 2V is by definition
P-P
equal to 10dBm, regardless of actual R .
L
640126f
5
LTC6401-26
TYPICAL PERFORMANCE CHARACTERISTICS
Frequency Response
Gain 0.1dB Flatness
30
25
20
15
10
5
1.0
0.8
TEST CIRCUIT B
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
TEST CIRCUIT B
0
10
100
FREQUENCY (MHz)
1000
3000
10
100
1000
3000
FREQUENCY (MHz)
640126 G02
640126 G01
Input and Output Reflection and
Reverse Isoloation vs Frequency
S21 Phase and Group Delay vs
Frequency
0
–50
0.8
0.6
0.4
0.2
0
0
–10
–20
–30
–40
–50
–60
–70
TEST CIRCUIT B
S11
S22
S12
GROUP DELAY
–100
–150
–200
PHASE
TEST CIRCUIT B
0
200
400
600
800
1000
10
100
1000
3000
FREQUENCY (MHz)
FREQUENCY (MHz)
640126 G04
640126 G03
Input and Output Impedance vs
Frequency
PSRR and CMRR vs Frequency
180
150
120
90
60
50
40
30
20
10
0
120
Z
Z
Z
Z
MAG
IN
OUT
MAG
PHASE
IN
OUT
100
80
60
40
20
0
PSRR
CMRR
PHASE
60
30
0
10
100
FREQUENCY (MHz)
1000
1
10
100
1000
FREQUENCY (MHz)
640126 G05
640126 G06
640126f
6
LTC6401-26
TYPICAL PERFORMANCE CHARACTERISTICS
Noise Figure and Input Referred
Noise Voltage vs Frequency
Small Signal Transient Response
1.35
1.30
1.25
1.20
1.15
9
8
7
6
5
2.0
1.5
1.0
0.5
0
R
= 87.5Ω PER OUTPUT
L
TEST CIRCUIT B
+OUT
EN
–OUT
NOISE FIGURE
0
2
4
6
8
10
1000
10
100
TIME (ns)
FREQUENCY (MHz)
640126 G07
640126 G08
Overdriven Transient Response
Large Signal Transient Response
2.5
2.0
1.5
1.0
0.5
0
2.5
R
L
= 87.5Ω PER OUTPUT
R
= 87.5Ω PER OUTPUT
L
TEST CIRCUIT B
–OUT
2.0
1.5
1.0
0.5
0
+OUT
–OUT
+OUT
TEST CIRCUIT B
50
0
100
150
200
250
0
4
8
12
16
20
TIME (ns)
TIME (ns)
640126 G10
640126 G09
1% Settling Time for
2V Output Step
Harmonic Distortion vs Frequency
–40
–50
5
DIFFERENTIAL INPUT
V
OUT
= 2V
4
3
P-P
–60
2
1
–70
0
–80
–1
–2
–3
–4
–5
–90
HD2 NO R
L
HD2 R = 200Ω
L
–100
–110
HD3 NO R
R
= 87.5Ω PER OUTPUT
L
L
HD3 R = 200Ω
TEST CIRCUIT B
L
200
0
1
2
3
4
5
0
50
100
150
TIME (ns)
FREQUENCY (MHz)
640126 G11
640126 G12
640126f
7
LTC6401-26
TYPICAL PERFORMANCE CHARACTERISTICS
Third Order Intermodulation
Distortion vs Frequency
Third Order Intermodulation
Distortion vs Frequency
Harmonic Distortion vs Frequency
–40
–50
–40
–50
–40
–50
DIFFERENTIAL INPUT
SINGLE-ENDED INPUT
SINGLE-ENDED INPUT
V
= 2V COMPOSITE
V
= 2V COMPOSITE
V
= 2V
OUT
P-P
OUT
P-P
OUT
P-P
–60
–60
–60
–70
–70
–70
–80
–80
–80
–90
–90
–90
HD2 NO R
L
HD2 R = 200Ω
L
–100
–110
–100
–110
–100
–110
NO R
L
NO R
L
L
HD3 NO R
L
L
R
= 200Ω
R
= 200Ω
HD3 R = 200Ω
L
200
0
50
100
150
200
200
0
50
100
150
0
150
50
100
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
640126 G13
640126 G14
640126 G15
Output 1dB Compression Point vs
Frequency
Equivalent Output Third Order
Intercept Point vs Frequency
60
50
19.0
18.5
DIFFERENTIAL INPUT
(NOTE 7)
DIFFERENTIAL INPUT
R
= 375Ω
L
TEST CIRCUIT A
(NOTE 7)
40
30
18.0
17.5
20
10
0
17.0
16.5
16.0
NO R
L
L
R
= 200Ω
0
50
100
150
200
0
50
100
150
200
FREQUENCY (MHz)
FREQUENCY (MHz)
640126 G17
640126 G16
Turn-On Time
Turn-Off Time
3.5
3.0
2.5
2.0
70
60
50
40
3.5
3.0
2.5
2.0
70
R
L
= 87.5Ω PER OUTPUT
R
L
= 87.5Ω PER OUTPUT
60
50
40
ENABLE
I
CC
–OUT
–OUT
+OUT
1.5
1.0
30
20
1.5
1.0
30
20
+OUT
0.5
0
10
0
0.5
0
10
0
I
CC
ENABLE
–0.5
–10
–0.5
–10
0
100
300
0
100
300
–100
400
500
–100
400
500
200
200
TIME (ns)
TIME (ns)
640126 G19
640126 G18
640126f
8
LTC6401-26
PIN FUNCTIONS
V (Pins 1, 3, 10): Positive Power Supply (Normally tied
to 3V or 3.3V). All three pins must be tied to the same
voltage. Bypass each pin with 1000pF and 0.1μF capaci-
tors as close to the pins as possible.
+
–OUTF, +OUTF (Pins 6, 7): Filtered Outputs. These pins
have 50Ω series resistors and a 2.7pF shunt capacitor.
ENABLE (Pin 11): This pin is a logic input referenced to
V . If low, the part is enabled. If high, the part is disabled
EE
V
(Pin 2): This pin sets the output common mode
and draws very low standby current while the internal op
OCM
voltage. An 0.1μF external bypass capacitor is recom-
amp has high output impedance.
mended.
+IN (Pins 13, 14): Positive Input. Pins 13 and 14 are
internally shorted together.
–
V (Pins 4, 9, 12, 17): Negative Power Supply. All four
pins must be connected to same voltage/ground.
–IN (Pins 15, 16): Negative Input. Pins 15 and 16 are
internally shorted together.
–OUT, +OUT (Pins 5, 8): Unfiltered Outputs. These pins
have series 12.5Ω resistors R
.
–
OUT
Exposed Pad (Pin 17): V . The Exposed Pad must be
connected to same voltage/ground as pins 4, 9, 12.
BLOCK DIAGRAM
–
+
–
V
ENABLE
V
V
12
11
10
9
BIAS CONTROL
R
F
500Ω
R
R
OUT
12.5Ω
G
+IN
13
+OUT
25Ω
8
R
FILT
+OUTF
50Ω
+IN
–IN
IN+
IN–
OUT–
7
14
15
C
FILT
R
FILT
2.7pF
–OUTF
–OUT
50Ω
6
5
OUT+
R
R
G
25Ω
R
OUT
12.5Ω
F
–IN
16
500Ω
2k
COMMON
MODE CONTROL
5.3pF
640126 BD
1
2
3
4
+
+
–
V
V
V
V
OCM
640126f
9
LTC6401-26
APPLICATIONS INFORMATION
Circuit Operation
them if the source is differential (Figure 1). Another ap-
proach is to employ a wideband transformer if the source
is single ended (Figure 2). Both methods provide a wide-
band match. Alternatively, one could apply a narrowband
impedance match at the inputs of the LTC6401-26 for
frequency selection and/or noise reduction.
The LTC6401-26 is a low noise and low distortion fully
differential op amp/ADC driver with:
• Operation from DC to 1.6GHz –3dB bandwidth
• Fixed gain of 20V/V (26dB)
ReferringtoFigure3,LTC6401-26canbeeasilyconfigured
for single-ended input and differential output without a
balun. The signal is fed to one of the inputs through a
matchingnetworkwhiletheotherinputisconnectedtothe
samematchingnetworkandasourceresistor.Becausethe
return ratios of the two feedback paths are equal, the two
outputshavethesamegainandthussymmetricalswing.In
general,thesingle-endedinputimpedanceandtermination
• Differential input impedance 50Ω
• Differential output impedance 25Ω
• Differential impedance of output filter 100Ω
TheLTC6401-26iscomposedofafullydifferentialamplifier
with on chip feedback and output common mode voltage
control circuitry. Differential gain and input impedance
are set by 25Ω/500Ω resistors in the feedback network.
Smalloutputresistorsof12.5Ωimprovethecircuitstability
over various load conditions. They also provide a possible
external filtering option, which is often desirable when the
load is an ADC.
resistor R are determined by the combination of R , R
T
S
G
and R . For example, when R is 50Ω, it is found that the
F
S
single-ended input impedance is 75Ω and R is 150Ω in
T
order to match to a 50Ω source impedance.
LTC6401-26
500Ω
25Ω
25Ω
12.5Ω
50Ω
Filter resistors of 50Ω are available for additional filtering.
Lowpass/bandpassfiltersareeasilyimplementedwithjust
a couple of external components. Moreover, they offer
single-ended 50Ω matching in wideband applications and
no external resistor is needed.
13 +IN
+OUT
8
IN+
IN–
OUT–
+OUTF
7
V
IN
14 +IN
15 –IN
+
–
50Ω
2.7pF
–OUTF
6
5
OUT+
500Ω
The LTC6401-26 is very flexible in terms of I/O coupling.
It can be AC- or DC-coupled at the inputs, the outputs or
both. Due to the internal connection between input and
output, users are advised to keep input common mode
voltage between 1V and 1.6V for proper operation. If the
inputs are AC-coupled, the input common mode voltage
25Ω
25Ω
12.5Ω
16 –IN
–OUT
640126 F01
Figure 1. Input Termination for Differential 50Ω Input Impedance
is automatically biased close to V
and thus no external
OCM
LTC6401-26
500Ω
50Ω
25Ω
12.5Ω
50Ω
circuitry is needed for bias. The LTC6401-26 provides an
output common mode voltage set by V , which allows
13 +IN
+OUT
8
OCM
driving ADC directly without external components such as
transformer or AC coupling capacitors. The input signal
can be either single-ended or differential with only minor
difference in distortion performance.
IN+
IN–
OUT–
1:1
+OUTF
7
V
IN
14 +IN
15 –IN
+
–
50Ω
2.7pF
–OUTF
6
5
OUT+
500Ω
25Ω
12.5Ω
16 –IN
–OUT
640126 F02
Input Impedance and Matching
M/A-COM
MABA-007159-000000
ThedifferentialinputimpedanceoftheLTC6401-26is50Ω.
The interface between the input of LTC6401-26 and 50Ω
source is straightforward. One way is to directly connect
Figure 2. Input Termination for Differential 50Ω Input Impedance
Using a Balun
640126f
10
LTC6401-26
APPLICATIONS INFORMATION
R
S
LTC6401-26
The internal low pass filter outputs at +OUTF/–OUTF have
a –3dB bandwidth of 590MHz. External capacitors can
reduce the low pass filter bandwidth as shown in Figure
5. A bandpass filter is easily implemented with only a
few components as shown in Figure 6. Three 39pF ca-
pacitors and 16nH inductor create a bandpass filter with
165MHz center frequency, –3dB frequencies at 138MHz
and 200MHz.
0.1μF
500Ω
50Ω
25Ω
12.5Ω
13 +IN
+OUT
8
V
IN
+
50Ω
–
R
T
IN+
IN–
OUT–
150Ω
+OUTF
7
14 +IN
15 –IN
0.1μF
50Ω
2.7pF
–OUTF
6
5
OUT+
500Ω
0.1μF
25Ω
12.5Ω
16 –IN
–OUT
640126 F03
37.4Ω
Output Common Mode Adjustment
Figure 3. Input Termination for Single-Ended 50Ω Input
The LTC6401-26’s output common mode voltage is set
Impedance
by the V
pin, which is a high impedance input. The
OCM
The LTC6401-26 is unconditionally stable, i.e. differential
stability factor Kf>1 and stability measure B1>0. However,
the overall differential gain is affected by both source
impedance and load impedance as shown in Figure 4:
output common mode voltage is capable of tracking V
OCM
control is
in a range from 1V to 1.6V. Bandwidth of V
OCM
typically 15MHz, which is dominated by a low pass filter
connected to the V pin and is aimed to reduce com-
OCM
mon mode noise generation at the outputs. The internal
common mode feedback loop has a –3dB bandwidth of
400MHz, allowing fast rejection of any common mode
VOUT
RL
RS +50 25+RL
1000
AV =
=
•
V
IN
output voltage disturbance. The V
pin should be tied
OCM
The noise performance of the LTC6401-26 also depends
upon the source impedance and termination. A trade-off
between gain and noise is obvious when constant noise
figure circle and constant gain circle are plotted within
the same input Smith Chart, based on which users can
choose the optimal source impedance for a given gain
and noise requirement.
to a DC bias voltage with a 0.1μF bypass capacitor. When
interfacing with 3V A/D converters such as the LTC22xx
families, the V
of the ADC.
pin can be connected to the V pin
OCM
CM
Driving A/D Converters
TheLTC6401-26hasbeenspecificallydesignedtointerface
directlywithhighspeedA/Dconverters.Figure7showsthe
LTC6401-26withsingle-endedinputdrivingtheLTC2208,
whichisa16-bit,130MspsADC.Twoexternal5Ωresistors
help eliminate potential resonance associated with bond
Output Impedance Match and Filter
TheLTC6401-26candriveanADCdirectlywithoutexternal
output impedance matching. Alternatively, the differential
output impedance of 25Ω can be made larger, e.g. 50Ω,
by series resistors or LC network.
wires of either the ADC input or the driver output. V
OCM
LTC6401-26
LTC6401-26
500Ω
500Ω
1/2 R
25Ω
12.5Ω
50Ω
1/2 R
25Ω
12.5Ω
50Ω
S
L
13 +IN
+OUT
8
13 +IN
+OUT
8
8pF
IN+
IN–
OUT–
IN+
IN–
OUT–
+OUTF
7
+OUTF
7
V
IN
FILTERED OUTPUT
(87.5MHz)
14 +IN
15 –IN
14 +IN
15 –IN
V
OUT
+
12pF
8pF
–
50Ω
50Ω
2.7pF
2.7pF
–OUTF
6
5
–OUTF
6
5
OUT+
500Ω
OUT+
500Ω
1/2 R
25Ω
12.5Ω
1/2 R
25Ω
12.5Ω
S
L
16 –IN
–OUT
16 –IN
–OUT
640126 F04
640126 F05
Figure 4. Calculate Differential Gain
Figure 5. LTC6401-26 Internal Filter Topology Modified for Low
Filter Bandwidth (Three External Capacitors)
640126f
11
LTC6401-26
APPLICATIONS INFORMATION
–40
–50
SINGLE-ENDED INPUT
= 122.8Msps
F
S
DRIVER V
= 2V COMPOSITE
OUT
P-P
–60
39pF
LTC6401-26
12.5Ω
–70
500Ω
25Ω
10Ω
4.99Ω
13 +IN
+OUT
8
–80
50Ω
IN+
IN–
OUT–
+OUTF
7
–90
14 +IN
15 –IN
16nH
39pF
LTC2208
1.7pF
50Ω
–100
–110
OUT+
500Ω
–OUTF
6
5
25Ω
12.5Ω
10Ω
4.99Ω
200
0
50
100
150
16 –IN
–OUT
640126 F06
FREQUENCY (MHz)
39pF
640126 F08
Figure 6. LTC6401-26 with 165MHz Output Bandpass Filter
Figure 8. IMD3 for the Combination of LTC6401-26 and LTC2208
of the LTC6401-26 is connected to V of the LTC2208
Test Circuit B uses a 4-port network analyzer to measure
S-parameters and gain/phase response. This removes the
effects of the wideband baluns and associated circuitry,
for a true picture of the >1GHz S-parameters and AC
characteristics.
CM
at 1.25V. Alternatively, a single-ended input signal can be
converted to a differential signal via a balun and fed to the
input of the LTC6401-26. Figure 8 summarizes the IMD3
performance of the whole system as shown in Figure 7.
Test Circuits
Due to the fully-differential design of the LTC6401 and
its usefulness in applications with differing characteristic
specifications, two test circuits are used to generate the
information in this datasheet. Test Circuit A is DC987B,
a two-port demonstration circuit for the LTC6401 family.
The silkscreen is shown in Figure 9. This circuit includes
input and output transformers (baluns) for single-ended-
to-differential conversion and impedance transformation,
allowing direct hook-up to a 2-port network analyzer.
There are also series resistors at the output to present the
LTC6401witha375Ωdifferentialload,optimizingdistortion
performance.Duetotheinputandoutputtransformers,the
–3dB bandwidth is reduced from 1.6GHz to 1.37GHz.
1.25V
0.1μF
0.1μF
V
OCM
4.99Ω
4.99Ω
+IN
V
–
+
CM
IF IN
150Ω
+OUT
AIN
AIN
+OUTF
–OUTF
LTC6401-26
LTC2208
0.1μF
–IN
ENABLE
–OUT
37.4Ω
LTC2208 130Msps
16-Bit ADC
26dB GAIN
640126 F07
Figure 7. Single-Ended Input to LTC6401-26 and LTC2208
Figure 9. Top Silkscreen for DC987B, Test Circuit A
640126f
12
LTC6401-26
TYPICAL APPLICATION
Demo Circuit 987B Schematic (Test Circuit A)
V
CC
ENABLE
DIS
1
3
V
CC
2
JP1
C17
1000pF
C18
0.1μF
R16
0Ω
12
–
11
10
+
9
–
V
ENABLE
V
V
R10
R2
(1)
R14
(1)
86.6Ω
13
14
15
16
8
7
6
5
+IN
+IN
–IN
+OUT
+OUTF
–OUTF
–OUT
R6
R12
T2
R8
(1)
C2
0.1μF
C4
0Ω
0Ω
R4
(2)
T1
(2)
5
4
1
2
3
3
2
1
TCM 4:19
1:4
4
J1
+IN
J4
+OUT
0.1μF
C21
0.1μF
R24
(1)
SL1
(2)
SL2
(2)
R7
(1)
LTC6401-26
R5
(1)
R11
(1)
SL3
0dB
6
(2)
J2
–IN
R3
(2)
C1
0.1μF
C3
0.1μF
J5
–OUT
R9
86.6Ω
–IN
V
R13
0Ω
C22
R1
0Ω
+
+
–
V
OCM
V
V
0.1μF
1
2
3
4
V
V
CC
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
0Ω
6
4
1
2
3
3
2
1
4
J6
TEST IN
J7
C23
C5
C19
0.1μF
C20
0.1μF
TEST OUT
0.1μF
0.1μF
R21
(1)
R22
(1)
R25
0Ω
R26
0Ω
C24
0.1μF
C6
0.1μF
6
V
CC
TP2
V
CC
NOTE: UNLESS OTHERWISE SPECIFIED.
(1) DO NOT STUFF.
C14
4.7μF
C15
1μF
2.85V TO 3.5V
(2) VERSION
-H
SL = SIGNAL LEVEL
IC
R3
R4
T1
SL1
SL2
SL3
TP3
GND
LTC6401UD-26 OPEN OPEN M/A-COM MABA-007159-000000 0dB
20dB 14dB
640126 TA02
640126f
13
LTC6401-26
TYPICAL APPLICATION
Test Circuit B, 4-Port Analysis
+
V
0.1μF
1000pF
–
+
–
V
ENABLE
V
V
12
G
11
10
9
BIAS CONTROL
R
F
500Ω
R
R
OUT
+IN
13
+OUT
37.4Ω
24.9Ω
25Ω
12.5Ω
PORT 1
PORT 3
8
(50Ω)
(50Ω)
R
FILT
0.1μF
0.1μF
+OUTF
50Ω
+IN
–IN
IN+
IN–
OUT–
7
14
15
1/2
AGILENT
E5O71A
1/2
AGILENT
E5O71A
C
FILT
R
50Ω
FILT
1.7pF
–OUTF
–OUT
6
5
OUT+
R
R
G
25Ω
R
OUT
12.5Ω
F
–IN
16
500Ω
24.9Ω
37.4Ω
PORT 2
(50Ω)
PORT 4
(50Ω)
0.1μF
0.1μF
COMMON
MODE CONTROL
640126 TA03
1
2
3
4
+
+
–
V
V
V
V
OCM
1000pF
0.1μF
0.1μF
+
V
V
OCM
640126f
14
LTC6401-26
PACKAGE DESCRIPTION
UD Package
16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691)
0.70 0.05
3.50 0.05
2.10 0.05
1.45 0.05
(4 SIDES)
PACKAGE OUTLINE
0.25 0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 × 45° CHAMFER
R = 0.115
TYP
0.75 0.05
3.00 0.10
(4 SIDES)
15 16
PIN 1
TOP MARK
(NOTE 6)
0.40 0.10
1
2
1.45 0.10
(4-SIDES)
(UD16) QFN 0904
0.200 REF
0.25 0.05
0.50 BSC
0.00 – 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
640126f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC6401-26
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
High-Speed Differential Amplifiers/Differential Op Amps
LT®1993-2
LT1993-4
LT1993-10
LT1994
800MHz Differential Amplifier/ADC Driver
900MHz Differential Amplifier/ADC Driver
700MHz Differential Amplifier/ADC Driver
Low Noise, Low Distortion Differential Op Amp
A = 2V/V, OIP3 = 38dBm at 70MHz
V
A = 4V/V, OIP3 = 40dBm at 70MHz
V
A = 2V/V, OIP3 = 40dBm at 70MHz
V
16-Bit SNR and SFDR at 1MHz, Rail-to-Rail Outputs
LT5514
Ultralow Distortion IF Amplifier/ADC Driver with Digitally
Controlled Gain
OIP3 = 47dBm at 100MHz, Gain Control Range 10.5dB to 33dB
LT5524
Low Distortion IF Amplifier/ADC Driver with Digitally
Controlled Gain
OIP3 = 40dBm at 100MHz, Gain Control Range 4.5dB to 37dB
LTC6400-20
LTC6400-26
LTC6401-8
LTC6401-20
LT6402-6
1.8GHz Low Noise, Low Distortion, Differential ADC Driver
1.9GHz Low Noise, Low Distortion, Differential ADC Driver
2.2GHz Low Noise, Low Distortion, Differential ADC Driver
1.3GHz Low Noise, Low Distortion, Differential ADC Driver
300MHz Differential Amplifier/ADC Driver
A = 20dB, 90mA Supply Current, IMD3 = –65dBc at 300MHz
V
A = 26dB, 85mA Supply Current, IMD3 = –71dBc at 300MHz
V
A = 8dB, 45mA Supply Current, IMD3 = –80dBc at 140MHz
V
A = 20dB, 50mA Supply Current, IMD3 = –74dBc at 140MHz
V
A = 6dB, Distortion < –80dBc at 25MHz
V
LT6402-12
LT6402-20
LTC6406
300MHz Differential Amplifier/ADC Driver
A = 12dB, Distortion < –80dBc at 25MHz
V
300MHz Differential Amplifier/ADC Driver
A = 20dB, Distortion < –80dBc at 25MHz
V
3GHz Rail-to-Rail Input Differential Op Amp
1.6nV/√Hz Noise, –72dBc Distortion at 50MHz, 18mA
LT6411
Low Power Differential ADC Driver/Dual Selectable Gain
Amplifier
16mA Supply Current, IMD3 = –83dBc at 70MHz, A = 1, –1 or 2
V
High-Speed Single-Ended Output Op Amps
LT1812/LT1813/ High Slew Rate Low Cost Single/Dual/Quad Op Amps
LT1814
8nV/√Hz Noise, 750V/μs, 3mA Supply Current
6nV/√Hz Noise, 1500V/μs, 6.5mA Supply Current
6nV/√Hz Noise, 2500V/μs, 9mA Supply Current
LT1815/LT1816/ Very High Slew Rate Low Cost Single/Dual/Quad Op Amps
LT1817
LT1818/LT1819 Ultra High Slew Rate Low Cost Single/Dual Op Amps
LT6200/LT6201 Rail-to-Rail Input and Output Low Noise Single/Dual Op Amps 0.95nV/√Hz Noise, 165MHz GBW, Distortion = –80dBc at 1MHz
LT6202/LT6203/ Rail-to-Rail Input and Output Low Noise Single/Dual/Quad
LT6204 Op Amps
1.9nV/√Hz Noise, 3mA Supply Current, 100MHz GBW
1.1nV/√Hz Noise, 3.5mA Supply Current, 215MHz GBW
1.9nV/√Hz Noise, 1.2mA Supply Current, 60MHz GBW
LT6230/LT6231/ Rail-to-Rail Output Low Noise Single/Dual/Quad Op Amps
LT6232
LT6233/LT6234/ Rail-to-Rail Output Low Noise Single/Dual/Quad Op Amps
LT6235
Integrated Filters
LTC1562-2
LT1568
Very Low Noise, 8th Order Filter Building Block
Very Low Noise, 4th Order Filter Building Block
Linear Phase, Tunable 10th Order Lowpass Filter
Very Low Noise Differential 2.5MHz Lowpass Filter
Very Low Noise Differential 5MHz Lowpass Filter
Very Low Noise Differential 10MHz Lowpass Filter
Very Low Noise Differential 15MHz Lowpass Filter
Very Low Noise Differential 20MHz Lowpass Filter
Lowpass and Bandpass Filters up to 300kHz
Lowpass and Bandpass Filters up to 10MHz
Single-Resistor Programmable Cut-Off to 300kHz
SNR = 86dB at 3V Supply, 4th Order Filter
SNR = 82dB at 3V Supply, 4th Order Filter
SNR = 82dB at 3V Supply, 4th Order Filter
SNR = 76dB at 3V Supply, 4th Order Filter
SNR = 76dB at 3V Supply, 4th Order Filter
LTC1569-7
LT6600-2.5
LT6600-5
LT6600-10
LT6600-15
LT6600-20
640126f
LT 0108 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
© LINEAR TECHNOLOGY CORPORATION 2008
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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