LTC6401IUD-8-TRPBF [Linear]
2.2GHz Low Noise, Low Distortion Differential ADC Driver for DC-140MHz; 2.2GHz的低噪声,低失真差分ADC驱动器为DC- 140MHz的型号: | LTC6401IUD-8-TRPBF |
厂家: | Linear |
描述: | 2.2GHz Low Noise, Low Distortion Differential ADC Driver for DC-140MHz |
文件: | 总16页 (文件大小:221K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC6401-8
2.2GHz Low Noise, Low
Distortion Differential ADC
Driver for DC-140MHz
FEATURES
DESCRIPTION
The LTC®6401-8 is a high-speed differential amplifier tar-
geted at processing signals from DC to 140MHz. The part
has been specifically designed to drive 12-, 14- and 16-bit
ADCs with low noise and low distortion, but can also be
used as a general-purpose broadband gain block.
■
2.2GHz –3dB Bandwidth
■
Fixed Gain of 2.5V/V (8dB)
■
–92dBc IMD3 at 70MHz (Equivalent OIP3 = 50dBm)
■
–80.5dBc IMD3 at 140MHz (Equivalent OIP3 = 44dBm)
■
1nV/√Hz Internal Op Amp Noise
■
12.1dB Noise Figure
The LTC6401-8 is easy to use, with minimal support cir-
cuitry required. The output common mode voltage is set
using an external pin, independent of the inputs, which
eliminates the need for transformers or AC-coupling ca-
pacitors in many applications. The gain is internally fixed
at 8dB (2.5V/V).
■
Differential Inputs and Outputs
■
400Ω Input Impedance
■
2.85V to 3.5V Supply Voltage
■
45mA Supply Current (135mW)
■
1V to 1.6V Output Common Mode, Adjustable
■
DC- or AC-Coupled Operation
Max Differential Output Swing 4.6V
■
The LTC6401-8 saves space and power compared to al-
ternative solutions using IF gain blocks and transformers.
The LTC6401-8 is packaged in a compact 16-lead 3mm ×
3mm QFN package and operates over the –40°C to 85°C
temperature range.
P-P
■
Small 16-Lead 3mm × 3mm × 0.75mm QFN Package
APPLICATIONS
■
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Differential ADC Driver
■
Differential Driver/Receiver
■
Single Ended to Differential Conversion
IF Sampling Receivers
SAW Filter Interfacing
■
■
TYPICAL APPLICATION
3.3V
3.3V
Equivalent Output IP3 vs Frequency
60
(NOTE 7)
C2
0.1μF
C1
1000pF
C
F2
33pF
50
40
+
V
C3
0.1μF
R
R
S3
S1
15Ω
10Ω
V
+
–
DD
+OUT
AIN
AIN
V
+IN
IN
30
20
10
0
R1
59.0Ω
L1
24nH
C
C4
0.1μF
F1
LTC6401-8
–OUT
LTC2208
R
15Ω
R
33pF
S2
S4
10Ω
–IN
V
V
CM
OCM
R2
C
F3
33pF
–
COILCRAFT
0603CS
27.4Ω
LTC2208
130Msps
V
1.25V
16-Bit ADC
64018 TA01a
0
20 40 60 80 100 120 140 160 180 200
C5
0.1μF
R3
100Ω
FREQUENCY (MHz)
64018 TA01b
64018f
1
LTC6401-8
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
Supply Voltage (V – V )......................................3.6V
CC
EE
Input Current (Note 2).......................................... 10mA
Operating Temperature Range
(Note 3) ............................................... –40°C to 85°C
Specified Temperature Range
(Note 4) ............................................... –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
Maximum Junction Temperature .......................... 150°C
16 15 14 13
+
–
V
1
2
3
4
12 V
V
11 ENABLE
+
OCM
+
17
V
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-8#PBF
LTC6401IUD-8#PBF
TAPE AND REEL
PART MARKING* PACKAGE DESCRIPTION
SPECIFIED TEMPERATURE RANGE
16-Lead (3mm × 3mm) Plastic QFN 0°C to 70°C
16-Lead (3mm × 3mm) Plastic QFN –40°C to 85°C
LTC6401CUD-8#TRPBF
LTC6401IUD-8#TRPBF
LCCY
LCCY
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
LTC6400 AND LTC6401 SELECTOR GUIDE Please check each datasheet for complete details.
PART NUMBER
GAIN
(dB)
GAIN
(V/V)
Z
IN
(DIFFERENTIAL)
I
CC
(mA)
(Ω)
LTC6401-8
LTC6401-20
LTC6401-26
LTC6400-20
LTC6400-26
8
2.5
10
20
10
20
400
200
50
45
20
26
20
26
50
45
200
50
90
85
In addition to the LTC6401 family of amplifiers, a lower distortion LTC6400 family is available. The LTC6400 is pin compatible to the LTC6401, and has the
same low noise performance. The LTC6400 shows higher linearity especially at input frequency above 140MHz at the expense of higher supply current.
Please refer to the separate LTC6400 data sheets for complete details. Other gain versions from 8dB to 14dB will follow.
64018f
2
LTC6401-8
DC ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at 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
●
●
●
●
●
●
●
●
G
Gain
V
V
=
=
400mV Differential
400mV Differential
7.5
8
8.5
dB
mdB/°C
mV
DIFF
IN
TC
Gain Temperature Drift
–0.5
89
GAIN
IN
V
V
V
Output Swing Low
Each Output, V
Each Output, V
=
=
1.6V Differential
1.6V Differential
170
SWINGMIN
SWINGMAX
OUTDIFFMAX
OUT
IN
IN
Output Swing High
2.3
2.42
4.6
V
Maximum Differential Output Swing
Output Current Drive
1dB Compressed
> 2V
V
P-P
I
V
10
–4
mA
mV
μV/°C
V
OUT
P-P,DIFF
V
Input Offset Voltage
Differential
Differential
4
1
OS
TCV
Input Offset Voltage Drift
Input Common Mode Voltage Range, MIN
Input Common Mode Voltage Range, MAX
Input Resistance (+IN, –IN)
Input Capacitance (+IN, –IN)
Output Resistance (+OUT, –OUT)
Filtered Output Resistance (+OUTF, –OUTF)
3
OS
VRMIN
VRMAX
I
I
1.6
V
●
Ω
R
Differential
340
400
1
460
INDIFF
INDIFF
C
Differential, Includes Parasitic
Differential
pF
●
●
Ω
R
R
18
85
25
32
OUTDIFF
OUTFDIFF
OUTFDIFF
Ω
Differential
100
2.7
55
115
C
Filtered Output Capacitance (+OUTF, –OUTF) Differential, Includes Parasitic
Common Mode Rejection Ratio Input Common Mode Voltage 1.1V~1.4V
Output Common Mode Voltage Control
pF
●
CMRR
36
dB
G
Common Mode Gain
V
OCM
= 1V to 1.6V
1
V/V
CM
V
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
OCM
= 1.1V to 1.5V
–15
15
15
mV
μV/°C
μA
OSCM
TCV
Common Mode Offset Voltage Drift
5
OSCM
IV
V
Input Current
OCM
3.6
OCM
ENABLE Pin
●
●
●
●
V
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
4
μA
μA
1.4
Power Supply
●
●
●
●
V
Operating Supply Range
Supply Current
2.85
36
3
3.5
60
3
V
mA
mA
dB
S
I
I
ENABLE = 0.8V, Input and Output Floating
ENABLE = 2.4V, Input and Output Floating
45
S
Shutdown Supply Current
0.8
73.5
SHDN
+
PSRR
Power Supply Rejection Ratio
(Differential Outputs)
V = 2.85V to 3.5V
50
64018f
3
LTC6401-8
AC ELECTRICAL CHARACTERISTICS Specifications are at 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
2.22
0.43
0.22
12.2
3400
2.3
MAX
UNITS
GHz
GHz
GHz
kHz
V/μs
ns
–3dB Bandwidth
200mV
200mV
200mV
(Note 6)
(Note 6)
(Note 6)
1
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
V
OUT
V
OUT
V
OUT
V
OUT
= 2V Step (Note 6)
t
t
t
t
1% Settling Time
Overdrive Recovery Time
Turn-On Time
= 2V (Note 6)
P-P
S1%
OVDR
ON
= 1.9V (Note 6)
18
ns
P-P
Within 10% of Final Values
79
ns
Turn-Off Time
I
Falls to 10% of Nominal
CC
193
14
ns
OFF
–3dBBW
V
Pin Small Signal –3dB BW
0.1V at V , Measured Single-Ended at
OCM
MHz
VOCM
OCM
P-P
Output (Note 6)
10MHz Input Signal
HD2,10M/HD3,10M Second/Third Order Harmonic Distortion
V
OUT
V
OUT
V
OUT
V
OUT
V
OUT
= 2V , R = 200Ω
–109/–88
–118/–100
–88
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
–93
P-P
L
Equivalent Third-Order Output Intercept
Point (f1 = 9.5MHz f2 = 10.5MHz)
= 2V Composite, No R (Note 7)
50.7
P-P
L
P1dB,10M
NF10M
1dB Compression Point
R = 375Ω (Notes 5, 7)
17.8
12.1
3.2
8
dBm
dB
L
Noise Figure
R = 375Ω (Note 5)
L
e
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
–91/–72
–100/–87
–83
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
–92
P-P
L
Equivalent Third-Order Output Intercept
Point (f1 = 69.5MHz f2 = 70.5MHz)
= 2V Composite, No R (Note 7)
50
P-P
L
P1dB,70M
NF70M
1dB Compression Point
R = 375Ω (Notes 5, 7)
18.3
12.2
3.2
dBm
dB
L
Noise Figure
R = 375Ω (Note 5)
L
e
e
Input Referred Voltage Noise Density
Output Referred Voltage Noise Density
Includes Resistors (Short Inputs)
Includes Resistors (Short Inputs)
nV/√Hz
nV/√Hz
IN,70M
7.9
ON,70M
64018f
4
LTC6401-8
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
–78/–59
–87/–70
–71
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
–80
P-P
L
OIP3,140M
Equivalent Third-Order Output Intercept
Point (f1 = 139.5MHz f2 = 140.5MHz)
= 2V Composite, No R (Note 7)
44.2
P-P
L
P1dB,140M
NF140M
1dB Compression Point
R = 375Ω (Notes 5, 7)
18.7
12.3
3.1
dBm
dB
L
Noise Figure
R = 375Ω (Note 5)
L
e
e
Input Referred Voltage Noise Density
Output Referred Voltage Noise Density
Includes Resistors (Short Inputs)
Includes Resistors (Short Inputs)
nV/√Hz
nV/√Hz
dBc
IN,140M
ON,140M
7.9
IMD3,130M/150M Third-Order Intermodulation
(f1 = 130MHz f2 = 150MHz) Measure at
170MHz
V
= 2V Composite, R = 375Ω
–75
–67
OUT
P-P
L
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
performance from –40°C to 85°C but is not tested or QA sampled at these
temperatures. The LTC6401I is guaranteed to meet specified performance
from –40°C to 85°C.
Note 5: Input and output baluns used. See Test Circuit A.
Note 2: Input pins (+IN, –IN) are protected by steering diodes to either
supply. If the inputs go beyond either supply rail, the input current should
be limited to less than 10mA.
Note 3: The LTC6401C and LTC6401I are guaranteed functional over the
operating temperature range of –40°C to 85°C.
Note 6: Measured using Test Circuit B. R = 87.5Ω per output.
L
Note 7: Since the LTC6401-8 is a feedback amplifier with low output
impedance, a resistive load is not required when driving an AD converter.
Therefore, typical output power is very small. In order to compare the
LTC6401-8 with amplifiers that require 50Ω output load, the LTC6401-8
Note 4: The LTC6401C is guaranteed to meet specified performance from
0°C to 70°C. It is designed, characterized and expected to meet specified
output voltage swing driving a given R is converted to OIP3 and P as
if it were driving a 50Ω load. Using this modified convention, 2V is by
P-P
L 1dB
definition equal to 10dBm, regardless of actual R .
L
TYPICAL PERFORMANCE CHARACTERISTICS
S21 Phase and Group Delay vs
Frequency
Frequency Response
Gain 0.1dB Flatness
14
12
10
8
1.0
0.8
0
–50
0.7
0.6
0.5
0.4
0.3
TEST CIRCUIT B
TEST CIRCUIT B
TEST CIRCUIT B
0.6
0.4
6
0.2
4
0
–100
–150
–200
2
–0.2
–0.4
–0.6
–0.8
–1.0
0
–2
–4
–6
PHASE
GROUP DELAY
10
100
1000
3000
10
100
1000
3000
0
200
400
600
800
1000
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
64018 G01
64018 G02
64018 G03
64018f
5
LTC6401-8
TYPICAL PERFORMANCE CHARACTERISTICS
Input and Output Reflection and
Reverse Isolation vs Frequency
Input and Output Impedance vs
Frequency
PSRR and CMRR vs Frequency
0
–10
–20
–30
–40
–50
–60
–70
–80
500
450
400
350
300
250
200
150
100
50
100
80
80
70
60
50
40
30
20
10
0
TEST CIRCUIT B
PHASE
PSRR
IMPEDANCE MAGNITUDE
60
Z
IN
S11
S22
40
CMRR
Z
20
OUT
0
–20
–40
–60
–80
–100
Z
IN
S12
Z
OUT
0
10
100
1000
3000
10
100
FREQUENCY (MHz)
1000
1
10
100
1000
FREQUENCY (MHz)
FREQUENCY (MHz)
64018 G04
64018 G05
64018 G06
Noise Figure and Input Referred
Noise Voltage vs Frequency
Small Signal Transient Response
Large Signal Transient Response
1.35
2.5
2.0
1.5
1.0
0.5
0
20
18
16
14
12
10
5
4
3
2
1
0
R
= 87.5Ω PER OUTPUT
R = 87.5Ω PER OUTPUT
L
TEST CIRCUIT B
L
TEST CIRCUIT B
1.30
1.25
1.20
1.15
+OUT
–OUT
EN
+OUT
–OUT
NOISE FIGURE
0
2
4
6
8
10
0
4
8
12
16
20
10
100
1000
TIME (ns)
TIME (ns)
FREQUENCY (MHz)
64018 G08
64018 G09
64018 G07
1% Settling Time for 2V
Output Step
Overdrive Recovery Response
Harmonic Distortion vs Frequency
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
5
–40
–50
4
3
R
= 87.5Ω PER OUTPUT
DIFFERENTIAL INPUT
L
+IN
TEST CIRCUIT B
V
= 2V
OUT P-P
4
3
2
–60
2
1
1
0
–70
–IN
0
–1
–2
–3
–4
–5
–6
R
= 87.5Ω PER OUTPUT
L
–80
+OUT
–1
–2
–3
–4
–5
–90
HD2 NO R
L
HD2 200Ω R
L
L
–100
–110
HD3 NO R
HD3 200Ω R
L
–OUT
TEST CIRCUIT B
25
0
1
2
3
4
5
0
20 40 60 80 100 120 140 160 180 200
0
50
75
100
125
TIME (ns)
FREQUENCY (MHz)
TIME (ns)
64018 G11
64018 G12
64018 G10
64018f
6
LTC6401-8
TYPICAL PERFORMANCE CHARACTERISTICS
Third Order Intermodulation
Distortion vs Frequency
Third Order Intermodulation
Distortion vs Frequency
Harmonic Distortion vs Frequency
–40
–50
–40
–50
–40
–50
DIFFERENTIAL INPUT
SINGLE-ENDED INPUT
OUT P-P
SINGLE-ENDED INPUT
V
= 2V COMPOSITE
V = 2V COMPOSITE
V
= 2V
OUT
P-P
OUT
P-P
–60
–60
–60
200Ω R
L
200Ω R
–70
–70
–70
L
–80
–80
–80
NO R
L
NO R
L
–90
–90
–90
HD2 NO R
L
HD2 200Ω R
L
–100
–110
–100
–110
–100
–110
HD3 NO R
HD3 200Ω R
L
L
0
20 40 60 80 100 120 140 160 180 200
0
20 40 60 80 100 120 140 160 180 200
0
20 40 60 80 100 120 140 160 180 200
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
64018 G13
64018 G14
64018 G15
Equivalent Output 1dB
Compression Point vs Frequency
Equivalent Output Third Order
Intercept Point vs Frequency
20
19
18
17
16
15
60
50
40
30
20
10
0
DIFFERENTIAL INPUT
R
= 375Ω
L
TEST CIRCUIT A (NOTE 7)
NO R
L
200Ω R
L
DIFFERENTIAL INPUT
(NOTE 7)
0
20 40 60 80 100 120 140 160 180 200
0
20 40 60 80 100 120 140 160 180 200
FREQUENCY (MHz)
FREQUENCY (MHz)
64018 G16
64018 G17
Turn-On Time
Turn-Off Time
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
70
60
50
40
30
20
10
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
70
60
50
40
30
20
10
0
R
L
= 87.5Ω PER OUTPUT
I
CC
+OUT
–OUT
–OUT
+OUT
I
CC
ENABLE
ENABLE
400
R
= 87.5Ω PER OUTPUT
L
–0.5
–10
–0.5
–10
–100
0
100
200
300
500
–100
0
100
200
TIME (ns)
300
400
500
TIME (ns)
64018 G18
64018 G19
64018f
7
LTC6401-8
PIN FUNCTIONS
V (Pins 1, 3, 10): Positive Power Supply (Normally tied
to 3V or 3.3V). All three pins must be tied to the same
voltage. Bypass each pin with 1000pF and 0.1μF capaci-
tors as close to the pins as possible.
+
–OUTF, +OUTF (Pins 6, 7): Filtered Outputs. These pins
have 50Ω series resistors and a 2.7pF shunt capacitor.
ENABLE (Pin 11): This pin is a logic input referenced to
V . If low, the part is enabled. If high, the part is disabled
EE
V
(Pin 2): This pin sets the output common mode
and draws very low standby current while the internal op
OCM
voltage. A 0.1μF external bypass capacitor is recom-
amp has high output impedance.
mended.
+IN (Pins 13, 14): Positive Input. Pins 13 and 14 are
internally shorted together.
–
V (Pins 4, 9, 12, 17): Negative Power Supply. All four
pins must be connected to same voltage/ground.
–IN (Pins 15, 16): Negative Input. Pins 15 and 16 are
internally shorted together.
–OUT, +OUT (Pins 5, 8): Unfiltered Outputs. These pins
have series resistors, R
12.5Ω.
–
OUT
Exposed Pad (Pin 17): V . The Exposed Pad must be
connected to same voltage/ground as pins 4, 9, 12.
BLOCK DIAGRAM
–
+
–
V
ENABLE
V
V
12
11
10
9
BIAS CONTROL
R
F
R
R
OUT
G
+IN
13
+OUT
500Ω
200Ω
12.5Ω
8
7
R
FILT
+OUTF
50Ω
+IN
–IN
IN+
IN–
OUT–
14
15
C
FILT
R
FILT
2.7pF
–OUTF
–OUT
50Ω
6
5
OUT+
R
R
G
200Ω
R
OUT
12.5Ω
F
–IN
16
500Ω
2k
COMMON
MODE CONTROL
5.3pF
64018 BD
1
2
3
4
+
+
–
V
V
V
V
OCM
64018f
8
LTC6401-8
APPLICATIONS INFORMATION
Circuit Operation
Input Impedance and Matching
The LTC6401-8 is a low noise and low distortion fully
differential op amp/ADC driver with:
ThedifferentialinputimpedanceoftheLTC6401-8is400Ω.
Usually the differential inputs need to be terminated to a
lower value impedance, e.g. 50Ω, in order to provide an
impedancematchforthesource.Severalchoicesareavail-
able. One approach is to use a differential shunt resistor
(Figure 1). Another approach is to employ a wideband
transformer and shunt resistor (Figure 2). Both methods
provide a wideband match. The termination resistor or
the transformer must be placed close to the input pins in
order to minimize the reflection due to input mismatch.
Alternatively, one could apply a narrowband impedance
match at the inputs of the LTC6401-8 for frequency selec-
tion and/or noise reduction.
• Operation from DC to 2.2GHz –3dB bandwidth
• Fixed gain of 2.5V/V (8dB)
• Differential input impedance 400Ω
• Differential output impedance 25Ω
• Differential impedance of output filter 100Ω
TheLTC6401-8iscomposedofafullydifferentialamplifier
with on chip feedback and output common mode voltage
control circuitry. Differential gain and input impedance
are set by 200Ω/500Ω resistors in the feedback network.
Smalloutputresistorsof12.5Ωimprovethecircuitstability
over various load conditions. They also provide a possible
external filtering option, which is often desirable when the
load is an ADC.
LTC6401-8
500Ω
25Ω
200Ω
12.5Ω
50Ω
13 +IN
+OUT
8
7
IN+
IN–
OUT–
+OUTF
V
IN
14 +IN
+
57.6Ω
–
Filter resistors of 50Ω are available for additional filtering.
Lowpass/bandpassfiltersareeasilyimplementedwithjust
a couple of external components. Moreover, they offer
single-ended 50Ω matching in wideband applications and
no external resistor is needed.
50Ω
2.7pF
15 –IN
–OUTF
6
5
OUT+
500Ω
25Ω
200Ω
12.5Ω
16 –IN
–OUT
64018 F01
Figure 1. Input Termination for Differential 50Ω Input Impedance
The LTC6401-8 is very flexible in terms of I/O coupling.
It can be AC- or DC-coupled at the inputs, the outputs or
both. Due to the internal connection between input and
output, users are advised to keep input common mode
voltage between 1V and 1.6V for proper operation. If the
inputs are AC-coupled, the input common mode voltage
Using Shunt Resistor
LTC6401-8
500Ω
25Ω
200Ω
12.5Ω
50Ω
13 +IN
14 +IN
+OUT
8
7
1:4
isautomaticallybiasedapproximately250mVaboveV
IN+
IN–
OUT–
OCM
+OUTF
V
IN
•
and thus no external circuitry is needed for bias. The
+
402Ω
–
•
50Ω
2.7pF
LTC6401-8 provides an output common mode voltage
15 –IN
–OUTF
6
5
OUT+
500Ω
set by V , which allows driving ADC directly without
OCM
25Ω
200Ω
12.5Ω
external components such as transformer or AC coupling
capacitors. The input signal can be either single-ended
or differential with only minor difference in distortion
performance.
16 –IN
–OUT
64018 F02
MINI CIRCUITS
TCM4-19
Figure 2. Input Termination for Differential 50Ω Input Impedance
Using a Balun
64018f
9
LTC6401-8
APPLICATIONS INFORMATION
LTC6401-8
+OUT
Referring to Figure 3, LTC6401-8 can be easily configured
for single-ended input and differential output without a
balun. The signal is fed to one of the inputs through a
matching network while the other input is connected to
thesamematchingnetworkandasourceresistor.Because
the return ratios of the two feedback paths are equal, the
two outputs have the same gain and thus symmetrical
swing. In general, the single-ended input impedance and
500Ω
1/2 R
200Ω
12.5Ω
50Ω
1/2 R
L
S
13 +IN
8
7
IN+
IN–
OUT–
+OUTF
V
IN
14 +IN
15 –IN
V
OUT
+
–
50Ω
2.7pF
–OUTF
6
5
OUT+
500Ω
1/2 R
200Ω
12.5Ω
1/2 R
L
S
16 –IN
–OUT
64018 F04
terminationresistorR aredeterminedbythecombination
T
Figure 4. Calculate Differential Gain
of R , R and R . For example, when R is 50Ω, it is found
S
G
F
S
that the single-ended input impedance is 322Ω and R is
T
and noise is obvious when constant noise figure circle
and constant gain circle are plotted within the input Smith
Chart,basedonwhichuserscanchoosetheoptimalsource
impedance for a given gain and noise requirement.
59Ω in order to match to a 50Ω source impedance.
R
LTC6401-8
S
0.1μF
500Ω
50Ω
200Ω
12.5Ω
50Ω
13 +IN
+OUT
8
7
V
IN
+
–
R
T
Output Impedance Match and Filter
IN+
IN–
OUT–
59.0Ω
+OUTF
14 +IN
15 –IN
0.1μF
The LTC6401-8 can drive an ADC directly without external
output impedance matching. Alternatively, the differential
output impedance of 25Ω can be made larger, e.g. 50Ω,
by series resistors or LC network.
50Ω
2.7pF
–OUTF
6
5
OUT+
500Ω
0.1μF
200Ω
12.5Ω
16 –IN
–OUT
64018 F03
27.4Ω
The internal low pass filter outputs at +OUTF/–OUTF
have a –3dB bandwidth of 590MHz. External capacitors
can reduce the lowpass filter bandwidth as shown in
Figure 5. A bandpass filter is easily implemented with
Figure 3. Input Termination for Single-Ended 50Ω Input
Impedance
The LTC6401-8 is unconditionally stable, i.e. differential
stability factor Kf>1 and stability measure B1>0. However,
the overall differential gain is affected by both source
impedance and load impedance as shown in Figure 4:
LTC6401-8
500Ω
200Ω
12.5Ω
50Ω
13 +IN
+OUT
8
7
8pF
FILTERED OUTPUT
IN+
IN–
OUT–
+OUTF
14 +IN
15 –IN
12pF
(87.5MHz)
VOUT
RL
RS + 400 25+RL
50Ω
1000
2.7pF
AV =
=
•
–OUTF
6
5
OUT+
500Ω
V
8pF
IN
200Ω
12.5Ω
16 –IN
–OUT
The noise performance of the LTC6401-8 also depends
uponthesourceimpedanceandtermination. Forexample,
an input 1:4 transformer in Figure 2 improves SNR by
adding 6dB gain at the inputs. A trade-off between gain
64018 F05
Figure 5. LTC6401-8 Internal Filter Topology Modified for Low
Filter Bandwidth (Three External Capacitors)
64018f
10
LTC6401-8
APPLICATIONS INFORMATION
1.25V
only a few components as shown in Figure 6. Three
39pF capacitors and a 16nH inductor create a bandpass
filter with 165MHz center frequency, –3dB frequencies at
138MHz and 200MHz.
0.1μF
0.1μF
0.1μF
V
OCM
+OUT
+OUTF
4.99Ω
V
–
+
CM
IF IN
59.0Ω
+IN
AIN
LTC6401-8
LTC2208
–OUTF
39pF
–IN
ENABLE
–OUT
AIN
LTC6401-8
12.5Ω
4.99Ω
500Ω
200Ω
10Ω
4.99Ω
27.4Ω
LTC2208 130Msps
16-Bit ADC
13 +IN
+OUT
8
7
8dB GAIN
64018 F07
50Ω
IN+
IN–
OUT–
+OUTF
14 +IN
15 –IN
Figure 7. Single-Ended Input to LTC6401-8 and LTC2208
16nH
LTC2208
1.7pF
39pF
50Ω
OUT+
500Ω
–OUTF
6
5
LTC6401-8 with single-ended input driving the LTC2208,
whichisa16-bit,130MspsADC.Twoexternal5Ωresistors
help eliminate potential resonance associated with bond
wires of either the ADC input or the driver output. V
of the LTC6401-8 is connected to V of the LTC2208 at
1.25V. Alternatively, an input single-ended signal can be
converted to differential signal via a balun and fed to the
input of the LTC6401-8.
200Ω
12.5Ω
10Ω
4.99Ω
16 –IN
–OUT
64018 F06
39pF
OCM
Figure 6. LTC6401-8 Modified 165MHz for Bandpass Filtering
(Three External Capacitors, One External Inductor)
CM
Output Common Mode Adjustment
The LTC6401-8’s output common mode voltage is set
Figure 8 summarizes the IMD3 performance of the whole
system as shown in Figure 7.
by the V
pin, which is a high impedance input. The
OCM
output common mode voltage is capable of tracking V
OCM
control is
in a range from 1V to 1.6V. Bandwidth of V
–40
OCM
SINGLE-ENDED INPUT
typically 14MHz, which is dominated by a low pass filter
connected to the V pin and is aimed to reduce com-
F
= 122.8Msps
S
–50
–60
DRIVER V
= 2V COMPOSITE
OUT
P-P
OCM
mon mode noise generation at the outputs. The internal
common mode feedback loop has a –3dB bandwidth
around 400MHz, allowing fast rejection of any common
–70
–80
mode output voltage disturbance. The V
pin should
OCM
–90
be tied to a DC bias voltage with a 0.1μF bypass capaci-
tor. When interfacing with 3V A/D converters such as the
–100
–110
LT22xx families, the V
pin can be connected to the
OCM
V
pin of the ADC.
0
20 40 60 80 100 120 140 160 180 200
CM
FREQUENCY (MHz)
64018 F08
Driving A/D Converters
Figure 8. IMD3 for the Combination of LTC6401-8 and LTC2208
TheLTC6401-8hasbeenspecificallydesignedtointerface
directlywithhighspeedA/Dconverters.Figure7showsthe
64018f
11
LTC6401-8
APPLICATIONS INFORMATION
Test Circuits
Due to the fully-differential design of the LTC6401 and
its usefulness in applications with differing characteristic
specifications, two test circuits are used to generate the
information in this datasheet. Test Circuit A is DC987B,
a two-port demonstration circuit for the LTC6401 family.
The silkscreen is shown in Figure 9. This circuit includes
input and output transformers (baluns) for single-ended-
to-differential conversion and impedance transformation,
allowing direct hook-up to a 2-port network analyzer.
There are also series resistors at the output to present
the LTC6401 with a 375Ω differential load, optimizing
distortionperformance. Duetotheinputandoutputtrans-
formers, the –3dB bandwidth is reduced from 2.2GHz to
approximately 1.65GHz.
Test Circuit B uses a 4-port network analyzer to measure
S-parameters and gain/phase response. This removes the
effects of the wideband baluns and associated circuitry,
for a true picture of the >1GHz S-parameters and AC
characteristics.
Figure 9. Top Silkscreen for DC987B. Test Circuit A
64018f
12
LTC6401-8
TYPICAL APPLICATIONS
Demo Circuit 987B Schematic (Test Circuit A)
V
CC
ENABLE
DIS
1
3
V
CC
2
JP1
C17
1000pF
C18
0.1μF
R16
0Ω
12
–
11
10
+
9
–
V
ENABLE
V
V
R10
R2
(1)
R14
(1)
86.6Ω
13
14
15
16
8
7
6
5
+IN
+IN
–IN
+OUT
+OUTF
–OUTF
–OUT
R6
0Ω
R12
0Ω
T2
TCM 4:19
1:4
R8
(1)
C2
0.1μF
C4
R4
(2)
T1
(2)
6
4
1
2
3
3
2
1
4
6
J1
+IN
J4
+OUT
0.1μF
C21
0.1μF
R24
(1)
SL1
(2)
SL2
(2)
R7
(1)
LTC6401-8
R5
(1)
R11
(1)
SL3
(2)
J5
–OUT
0dB
J2
–IN
R3
(2)
C1
0.1μF
C3
0.1μF
R9
86.6Ω
–IN
V
R13
0Ω
C22
R1
0Ω
+
+
–
V
V
V
0.1μF
OCM
1
2
3
4
V
CC
V
CC
C10
0.1μF
C9
1000pF
C12
1000pF
C13
0.1μF
V
CC
R19
1.5k
TP5
V
OCM
R20
1k
C7
0.1μF
T3
TCM 4:19
1:4
T4
TCM 4:19
1:4
R17
R18
0Ω
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
-E
SL = SIGNAL LEVEL
IC
R3
R4
T1
SL1
SL2
SL3
2dB
TP3
GND
LTC6401CUD-8 200Ω 200Ω MINI-CIRCUITS TCM4-19 (1:4) 6dB
8dB
64018 TA02
64018f
13
LTC6401-8
TYPICAL APPLICATIONS
Test Circuit B, 4-Port Analysis
+
V
1000pF
0.1μF
–
+
–
V
V
ENABLE
V
12
G
11
10
9
BIAS CONTROL
R
F
500Ω
R
R
OUT
+IN
13
+OUT
37.4Ω
200Ω
12.5Ω
PORT 1
(50Ω)
PORT 3
(50Ω)
8
7
R
FILT
50Ω
0.1μF
0.1μF
+OUTF
+IN
–IN
IN+
IN–
OUT–
14
15
1/2
AGILENT
E5O71A
1/2
AGILENT
E5O71A
C
FILT
2.7pF
R
50Ω
FILT
133Ω
–OUTF
–OUT
6
5
OUT+
R
R
G
200Ω
R
OUT
12.5Ω
F
–IN
16
500Ω
37.4Ω
PORT 2
(50Ω)
PORT 4
(50Ω)
0.1μF
0.1μF
COMMON
MODE CONTROL
64018 TA03
1
2
3
4
+
+
–
V
V
V
V
OCM
1000pF
0.1μF
0.1μF
+
V
V
OCM
64018f
14
LTC6401-8
PACKAGE DESCRIPTION
UD Package
16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691)
0.70 0.05
3.50 0.05
2.10 0.05
1.45 0.05
(4 SIDES)
PACKAGE OUTLINE
0.25 0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 × 45° CHAMFER
R = 0.115
TYP
0.75 0.05
3.00 0.10
(4 SIDES)
15 16
PIN 1
TOP MARK
(NOTE 6)
0.40 0.10
1
2
1.45 0.10
(4-SIDES)
(UD16) QFN 0904
0.200 REF
0.25 0.05
0.50 BSC
0.00 – 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
64018f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC6401-8
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
High-Speed Differential Amplifiers/Differential Op Amps
LT®1993-2
LT1993-4
LT1993-10
LT1994
800MHz Differential Amplifier/ADC Driver
900MHz Differential Amplifier/ADC Driver
700MHz Differential Amplifier/ADC Driver
Low Noise, Low Distortion Differential Op Amp
A = 2V/V, OIP3 = 38dBm at 70MHz
V
A = 4V/V, OIP3 = 40dBm at 70MHz
V
A = 10V/V, OIP3 = 40dBm at 70MHz
V
16-Bit SNR and SFDR at 1MHz, Rail-to-Rail Outputs
LT5514
Ultralow Distortion IF Amplifier/ADC Driver with Digitally
Controlled Gain
OIP3 = 47dBm at 100MHz, Gain Control Range 10.5dB to 33dB
LT5524
Low Distortion IF Amplifier/ADC Driver with Digitally
Controlled Gain
OIP3 = 40dBm at 100MHz, Gain Control Range 4.5dB to 37dB
LTC6400-20
LTC6400-26
LTC6401-20
LTC6401-26
LT6402-6
1.8GHz Low Noise, Low Distortion, Differential ADC Driver
1.9GHz Low Noise, Low Distortion, Differential ADC Driver
1.3GHz Low Noise, Low Distortion, Differential ADC Driver
1.6GHz Low Noise, Low Distortion, Differential ADC Driver
300MHz Differential Amplifier/ADC Driver
A = 20dB, 90mA Supply Current, IMD3 = –65dBc at 300MHz
V
A = 26dB, 85mA Supply Current, IMD3 = –71dBc at 300MHz
V
A = 20dB, 50mA Supply Current, IMD3 = –74dBc at 140MHz
V
A = 26dB, 45mA Supply Current, IMD3 = –72dBc at 140MHz
V
A = 6dB, Distortion < –80dBc at 25MHz
V
LT6402-12
LT6402-20
LTC6404-1
LTC6406
300MHz Differential Amplifier/ADC Driver
A = 12dB, Distortion < –80dBc at 25MHz
V
300MHz Differential Amplifier/ADC Driver
A = 20dB, Distortion < –80dBc at 25MHz
V
600MHz Low Noise Differential ADC Driver
e = 1.5nV/√Hz, Rail-to-Rail Outputs
n
3GHz Rail-to-Rail Input Differential Op Amp
1.6nV/√Hz Noise, –72dBc Distortion at 50MHz, 18mA
LT6411
Low Power Differential ADC Driver/Dual Selectable Gain
Amplifier
16mA Supply Current, IMD3 = –83dBc at 70MHz, A = 1, –1 or 2
V
High-Speed Single-Ended Output Op Amps
LT1812/LT1813/ High Slew Rate Low Cost Single/Dual/Quad Op Amps
LT1814
8nV/√Hz Noise, 750V/μs, 3mA Supply Current
6nV/√Hz Noise, 1500V/μs, 6.5mA Supply Current
6nV/√Hz Noise, 2500V/μs, 9mA Supply Current
LT1815/LT1816/ Very High Slew Rate Low Cost Single/Dual/Quad Op Amps
LT1817
LT1818/LT1819 Ultra High Slew Rate Low Cost Single/Dual Op Amps
LT6200/LT6201 Rail-to-Rail Input and Output Low Noise Single/Dual Op Amps 0.95nV/√Hz Noise, 165MHz GBW, Distortion = –80dBc at 1MHz
LT6202/LT6203/ Rail-to-Rail Input and Output Low Noise Single/Dual/Quad
LT6204 Op Amps
1.9nV/√Hz Noise, 3mA Supply Current, 100MHz GBW
1.1nV/√Hz Noise, 3.5mA Supply Current, 215MHz GBW
1.9nV/√Hz Noise, 1.2mA Supply Current, 60MHz GBW
LT6230/LT6231/ Rail-to-Rail Output Low Noise Single/Dual/Quad Op Amps
LT6232
LT6233/LT6234/ Rail-to-Rail Output Low Noise Single/Dual/Quad Op Amps
LT6235
Integrated Filters
LTC1562-2
LT1568
Very Low Noise, 8th Order Filter Building Block
Very Low Noise, 4th Order Filter Building Block
Linear Phase, Tunable 10th Order Lowpass Filter
Very Low Noise Differential 2.5MHz Lowpass Filter
Very Low Noise Differential 5MHz Lowpass Filter
Very Low Noise Differential 10MHz Lowpass Filter
Very Low Noise Differential 15MHz Lowpass Filter
Very Low Noise Differential 20MHz Lowpass Filter
Lowpass and Bandpass Filters up to 300kHz
Lowpass and Bandpass Filters up to 10MHz
Single-Resistor Programmable Cut-Off to 300kHz
SNR = 86dB at 3V Supply, 4th Order Filter
SNR = 82dB at 3V Supply, 4th Order Filter
SNR = 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
64018f
LT 1207 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
© LINEAR TECHNOLOGY CORPORATION 2007
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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