TI1 LMH6702-MIL 1.7-ghz ultra-low distortion wideband op amp Datasheet

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LMH6702-MIL
SNOSD58 – JUNE 2017
LMH6702-MIL 1.7-GHz Ultra-Low Distortion Wideband Op Amp
1 Features
3 Description
VS = ±5 V, TA = 25°C, AV = 2V/V, RL = 100 Ω,
VOUT = 2 VPP, Typical Unless Noted:
1
•
•
•
•
•
•
•
•
•
2nd and 3rd Harmonics (5 MHz, SOT-23) −100/−96
dBc
−3-dB Bandwidth (VOUT = 0.5 VPP) 1.7 GHz
Low Noise 1.83 nV/√Hz
Fast Settling to 0.1% 13.4 ns
Fast Slew Rate 3100 V/μs
Supply Current 12.5 mA
Output Current 80 mA
Low Intermodulation Distortion (75 MHz) −67 dBc
Improved Replacement for CLC409 and CLC449
2 Applications
•
•
•
•
•
•
Flash A-D Driver
D-A Transimpedance Buffer
Wide Dynamic Range IF Amp
Radar and Communication Receivers
Line Driver
High Resolution Video
The LMH6702-MIL is a very wideband, DC-coupled
monolithic operational amplifier designed specifically
for wide dynamic range systems requiring exceptional
signal fidelity. Benefitting from current feedback
architecture, the LMH6702-MIL offers unity gain
stability at exceptional speed without need for
external compensation.
With its 720-MHz bandwidth (AV = 2 V/V, VO = 2 VPP),
10-bit distortion levels through 60-MHz (RL = 100 Ω),
1.83-nV/√Hz input referred noise and 12.5-mA supply
current, the LMH6702-MIL is the ideal driver or buffer
for high-speed flash A-D and D-A converters.
Wide dynamic range systems such as radar and
communication receivers that require a wideband
amplifier offering exceptional signal purity will find the
low input referred noise and low harmonic and
intermodulation distortion of the LMH6702-MIL an
attractive high speed solution.
The LMH6702-MIL is constructed using VIP10™
complimentary bipolar process and proven current
feedback architecture. The LMH6702-MIL is available
in SOIC and SOT-23 packages.
Device Information(1)
PART NUMBER
LMH6702-MIL
PACKAGE
BODY SIZE (NOM)
SOIC (8)
4.90 mm × 3.91 mm
SOT-23 (5)
2.90 mm × 1.60 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Inverting Frequency Response
1
AV = -1
GAIN
-180
-230
-3
AV = -4
-4
-5
-280
-6
-7
1M
10M
100M
Frequency (Hz)
-65
-70
HD2, RL = 100 :
-75
-80
HD3, RL = 100 :
-330
-85
-380
-90
-95
AV = -10
-430
1G
HD2, RL = 1 k:
-60
HD (dBc)
PHASE
Phase (°)
-130
-1
Gain (dB)
-40
-45
-50
-55
AV = -2 -80
0
-2
Harmonic Distortion vs Load and Frequency
-30
-100
-105
1M
HD3, RL = 1 k:
10M
Frequency (Hz)
100M
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LMH6702-MIL
SNOSD58 – JUNE 2017
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Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
6.6
4
4
4
4
5
7
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
7.3 Device Functional Modes........................................ 12
8
Application and Implementation ........................ 13
8.1 Application Information............................................ 13
8.2 Typical Application ................................................. 13
9 Power Supply Recommendations...................... 15
10 Layout................................................................... 15
10.1 Layout Guidelines ................................................. 15
10.2 Layout Example .................................................... 16
11 Device and Documentation Support ................. 17
11.1
11.2
11.3
11.4
11.5
Detailed Description ............................................ 11
7.1 Overview ................................................................. 11
7.2 Feature Description................................................. 11
Documentation Support .......................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
17
17
17
17
17
12 Mechanical, Packaging, and Orderable
Information ........................................................... 17
4 Revision History
2
DATE
REVISION
NOTES
June 2017
*
Initial release.
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5 Pin Configuration and Functions
DBV Package
5-Pin SOT-23
Top View
D Package
8-Pin SOIC
Top View
1
5
OUT
+
V
N/C
-IN
V
-
2
8
-
7
+
6
N/C
V
+
2
+
+IN
1
+IN
4
3
-IN
V
-
3
4
5
OUT
N/C
NC: No internal connection
Pin Functions
PIN
NAME
NUMBER
I/O
DESCRIPTION
D
DBV
-IN
2
4
I
Inverting input voltage
+IN
3
3
I
Non-inverting input voltage
N/C
1, 5, 8
–
–
No connection
OUT
6
1
O
Output
V-
4
2
I
Negative supply
V+
7
5
I
Positive supply
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
(1) (2)
MIN
VS
IOUT
MAX
UNIT
±6.75
V
See
Common mode input voltage
V− to V+
V
150
°C
Maximum junction temperature
−65
Storage temperature
Soldering information
(1)
(2)
(3)
(3)
150
°C
Infrared or convection (20 s)
235
°C
Wave soldering (10 s)
260
°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
If Military/Aerospace specified devices are required, please contact the TI Sales Office/ Distributors for availability and specifications.
The maximum output current (IOUT) is determined by device power dissipation limitations.
6.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001
(1)
±2000
Machine Model (MM), per JEDEC specification JESD22-C101, all pins (2)
±200
UNIT
V
Human body model: 1.5 kΩ in series with 100 pF. JEDEC document JEP155 states that 2000-V HBM allows safe manufacturing with a
standard ESD control process. Manufacturing with less than 2000-V HBM is possible with the necessary precautions. Pins listed as
±2000 V may actually have higher performance.
Machine model: 0 Ω in series with 200 pF. JEDEC document JEP157 states that 200-V MM allows safe manufacturing with a standard
ESD control process. Manufacturing with less than 200-V MM is possible with the necessary precautions. Pins listed as ±200 V may
actually have higher performance.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) (1)
Operating temperature
Nominal supply voltage
(1)
MIN
MAX
−40
85
UNIT
°C
±4
±6
V
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but specific performance is not ensured. For ensured specifications, see the Electrical
Characteristics tables.
6.4 Thermal Information
LMH6702-MIL
THERMAL METRIC
(1)
DBV (SOT-23)
D (SOIC)
5 PINS
8 PINS
UNIT
RθJA
Junction-to-ambient thermal resistance
182
133
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
139
79
°C/W
RθJB
Junction-to-board thermal resistance
40
73
°C/W
ψJT
Junction-to-top characterization parameter
28
28
°C/W
ψJB
Junction-to-board characterization parameter
40
73
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report (SPRA953).
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6.5 Electrical Characteristics
at AV = 2, VS = ±5 V, RL = 100 Ω, RF = 237 Ω (unless otherwise noted) (1)
PARAMETER
TEST CONDITIONS
MIN (2)
TYP (3)
MAX (2)
UNIT
FREQUENCY DOMAIN PERFORMANCE
SSBWSM
VOUT = 0.5 VPP
SSBWLG
VOUT = 2 VPP
720
VOUT = 4 VPP
480
VOUT = 2 VPP, AV = +10
140
LSBWLG
-3-dB Bandwidth
SSBWHG
1700
MHz
GF0.1dB
0.1-dB gain flatness
VOUT = 2 VPP
120
MHz
LPD
Linear phase deviation
DC to 100 MHz
0.09
deg
DG
Differential gain
DP
Differential phase
RL =150 Ω, 3.58 MHz
0.024%
RL =150 Ω, 4.43 MHz
0.021%
RL = 150 Ω, 3.58 MHz
0.004
RL = 150 Ω, 4.43 MHz
0.007
deg
TIME DOMAIN RESPONSE
tR
Rise time
tF
Fall time
OS
Overshoot
2-V Step, TRS
0.87
2-V Step, TRL
0.77
6-V Step, TRS
1.70
6-V Step, TRL
1.70
2-V Step
ns
ns
0%
SR
Slew rate
6 VPP, 40% to 60%
Ts
Settling time to 0.1%
2-V Step
(4)
3100
V/µs
13.4
ns
DISTORTION AND NOISE RESPONSE
2 VPP, 5 MHz (5) (SOT-23)
HD2L
HD2
2nd Harmonic distortion
HD2H
HD3L
HD3
−87
2VPP, 20 MHz (5) (SOT-23)
−79
2VPP, 20 MHz (5) (SOIC)
−72
2VPP, 60 MHz (5) (SOT-23)
−63
2VPP, 60 MHz (5) (SOIC)
−64
2VPP, 5 MHz (5) (SOT-23)
−96
2VPP, 5 MHz
3rd Harmonic distortion
HD3H
−100
2 VPP, 5 MHz (5) (SOIC)
(5)
(SOIC)
dBc
dBc
dBc
dBc
−98
2VPP, 20 MHz (5) (SOT-23)
−88
2VPP, 20 MHz (5) (SOIC)
−82
2VPP, 60 MHz (5) (SOT-23)
−70
2VPP, 60 MHz (5) (SOIC)
−65
dBc
dBc
OIM3
IMD
−67
dBc
VN
Input referred voltage noise >1 MHz
1.83
nV/√Hz
IN
Input referred inverting
noise current
>1 MHz
18.5
pA/√Hz
INN
Input referred non-inverting
noise current
>1 MHz
3.0
pA/√Hz
SNF
Total input noise floor
>1 MHz
−158
dBm1Hz
INV
Total integrated input noise
1 MHz to 150 MHz
(1)
(2)
(3)
(4)
(5)
75 MHz, PO = 10dBm/ tone
35
µV
Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very
limited self-heating of the device such that TJ = TA. No guarantee of parametric performance is indicated in the electrical tables under
conditions of internal self-heating where TJ > TA. Min/Max ratings are based on production testing unless otherwise specified.
All limits are ensured by testing or statistical analysis.
Typical numbers are the most likely parametric norm.
Slew Rate is the average of the rising and falling edges.
Harmonic distortion is strongly influenced by package type (SOT-23 or SOIC). See Application Note section under Harmonic Distortion
for more information.
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Electrical Characteristics (continued)
at AV = 2, VS = ±5 V, RL = 100 Ω, RF = 237 Ω (unless otherwise noted)(1)
PARAMETER
TEST CONDITIONS
MIN (2)
TYP (3)
MAX (2)
UNIT
STATIC, DC PERFORMANCE
±1.0
VIO
Input offset voltage
DVIO
Input offset voltage average
See (6)
drift
IBN
Input bias current
Non-Inverting (7)
DIBN
Input bias current average
drift
Non-Inverting (6)
IBI
Input bias current
Inverting (7)
DIBI
Input bias current average
drift
Inverting (6)
PSRR
Power supply rejection ratio DC
CMRR
Common mode rejection
ration
DC
ICC
Supply current
RL = ∞
-40 ≤ TJ ≤ 85
±4.5
±6.0
−13
−6
-40 ≤ TJ ≤ 85
µV/°C
–15
–21
+40
−8
-40 ≤ TJ ≤ 85
±30
−10
-40 ≤ TJ ≤ 85
52
dB
48
dB
44
11.0
-40 ≤ TJ ≤ 85
12.5
10.0
µA
nA/°C
45
45
-40 ≤ TJ ≤ 85
µA
nA/°C
±34
47
mV
16.1
17.5
mA
MISCELLANEOUS PERFORMANCE
RIN
Input resistance
Non-Inverting
1.4
CIN
Input capacitance
Non-Inverting
1.6
pF
ROUT
Output resistance
Closed Loop
30
mΩ
VOL
Output voltage range
RL = 100 Ω
CMIR
Input voltage range
Common Mode
IO
Output current
(6)
(7)
6
±3.3
-40 ≤ TJ ≤ 85
±3.5
±3.2
±1.9
±2.2
50
80
MΩ
V
V
mA
Drift determined by dividing the change in parameter at temperature extremes by the total temperature change.
Negative input current implies current flowing out of the device.
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6.6 Typical Characteristics
TA = 25°C, VS = ±5 V, RL = 100 Ω, Rf = 237 Ω (unless otherwise noted)
150
AV = +1
GAIN
AV = +2
-1
0
50
-1
-50
AV = +4
-4
-100
Gain (dB)
0
-3
AV = +2
-5
AV = -2 -80
-130
AV = +4
-2
-30
AV = -1
GAIN
Phase (°)
Gain (dB)
PHASE
1
100
PHASE
-2
-180
-230
-3
AV = -4
-4
-150
-5
-200
-6
Phase (°)
1
0
-280
-330
AV = -10
AV = +1
-6
-380
AV = +10
-7
1M
V0 = 2 Vpp
-7
1M
-250
1G
10M
100M
Frequency (Hz)
-430
1G
100M
Frequency (Hz)
RF = 237 Ω
RL = 100 Ω
VOUT = 2 VPP
Figure 1. Non-Inverting Frequency Response
1
10M
RL = 100 Ω
RF = 237 Ω
Figure 2. Inverting Frequency Response
1
GAIN
150
GAIN
0
100 :
0
100
-1
-1
50
PHASE
-4
0
-5
-54
-6
-108
-7
-162
-8
-9
10M
100M
1G
-2
-50
-4
-100
1 k:
1 k:
-5
-150
100 :
-216
-6
-270
10G
-7
-200
50 :
0
200M
Frequency (Hz)
VOUT = 0.5 VPP
0
50 :
-3
Phase (°)
-3
Gain (dB)
PHASE
Phase (°)
Gain (dB)
-2
400M
600M
800M
-250
1G
Frequency (Hz)
RF = 232 Ω
AV = 2
Figure 3. Small Signal Bandwidth
1
AV = 2
RF = 237 Ω
VO = 2 VPP
Figure 4. Frequency Response for Various RLs, AV = 2
150
1.5
GAIN
0
100
-1
50
1
50 :
-3
0
-50
-4
0.5
VOUT (V)
1 k:
Phase (°)
Gain (dB)
PHASE
-2
-100
50 :
-5
-0.5
AV = -2
-1
-200
100 :
-7
100M
0
-150
-6
0
AV = +2
200M
300M
400M
-250
500M
-1.5
0
Frequency (Hz)
AV = 4
VO = 2 VPP
2
4
6
8
10
12
14
Time (ns)
RF = 237 Ω
VO = 2 VPP
Figure 5. Frequency Response for Various RLs, AV = 4
RL = 100 Ω
Figure 6. Step Response, 2 VPP
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Typical Characteristics (continued)
TA = 25°C, VS = ±5 V, RL = 100 Ω, Rf = 237 Ω (unless otherwise noted)
4
1
3
2
0.1
Settling Error (%)
VOUT (V)
1
0
-1
-2
0.01
-3
-4
0.001
0
10
20
30
40
50
1
60
10
AV = 2
RL = 100 Ω
VOUT = 6 VPP
Figure 8. Percent Settling vs Time
-40
-50
HD2, RL = 1 k:
HD2, RL = 100 :
-75
-80
HD3, RL = 100 :
PS (dBc)
HD (dBc)
-65
-70
-70
-80
-85
-90
-90
-95
HD3, RL = 1 k:
-100
-105
1M
50 MHz
-100
25 MHz
10M
Frequency (Hz)
2 VPP
-110
-5
100M
AV = 2
RF = 237 Ω
Figure 9. Harmonic Distortion vs Load and Frequency
(SOIC Package)
100
-3
-1
1
3
AV = 2
RL = 100 Ω
-50
60MHz
-60
15
50
0.1% SETTLING
40
RS
10
30
20
5
-80
-90
-100
10
0
1
10
100
1k
0
10k
-110
-10
10MHz
5MHz
-5
0
5
10
15
20
POUT (dBm)
CL (pF)
AV = -1
20MHz
-70
HD (dBc)
70
Settling Time (ns)
20
60
RF = 237 Ω
Figure 10. 2 Tone 3rd Order Spurious Level
(SOIC Package)
25
80
5
Test Tone Power at 50 : Load (dBm)
0.05% SETTLING
90
RS (:)
75 MHz
-60
-60
AV = 2
RL = 1 kΩ
Figure 11. RS and Settling Time vs CL
8
1k
RL = 100 Ω
Figure 7. Step Response, 6 VPP
-40
-45
-50
-55
100
Time (ns)
Time (ns)
RF = 237 Ω
RL = 100 Ω
Figure 12. HD2 vs Output Power (Across 100 Ω)
(SOIC Package)
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Typical Characteristics (continued)
TA = 25°C, VS = ±5 V, RL = 100 Ω, Rf = 237 Ω (unless otherwise noted)
-50
0.5
UNIT 1
60 MHz
0
-60
-0.5
-70
VOS (mV)
HD (dBc)
-1
20 MHz
-80
-90
-1.5
-2
UNIT 2
-2.5
-100 10 MHz
UNIT 3
5 MHz
-3
-110
-3.5
-120
-10
-4
-5
0
5
10
15
20
-40
-15
POUT (dBm)
AV = 2
10
35
60
85
110
135
TEMPERATURE (°C)
RF = 237 Ω
RL = 100 Ω
Figure 13. HD3 vs Output Power (Across 100 Ω)
(SOIC Package)
Figure 14. Input Offset for 3 Representative Units
10
-4
UNIT 3
8
-5
6
-7
2
0
IBN (µA)
IBI (µA)
UNIT 3
-6
4
UNIT 2
-2
UNIT 2
-8
-9
UNIT 1
-4
-10
-6
UNIT 1
-11
-8
-10
-40
-15
10
35
60
85
110
-12
-40
135
-15
TEMPERATURE (°C)
Figure 15. Inverting Input Bias
for 3 Representative Units
10
35
60
85
TEMPERATURE (°C)
110
135
Figure 16. Non-Inverting Input Bias for 3 Representative
Units
15
70
1000
60
INVERTING CURRENT
NON-INVERTING
CURRENT
10
5
50
-5
- PSRR
40
-15
CMRR
30
-25
20
20 Log (RO)
100
CMRR/PSRR (dB)
Hz)
NOISE CURRENT (pA/
NOISE VOLTAGE (nV/
Hz)
+ PSRR
-35
RO
10
VOLTAGE
-45
1
100
1k
10k
100k
FREQUENCY (Hz)
1M
10M
0
1k
10k
VS = ±5 V
Figure 17. Noise
100k
1M
Frequency (Hz)
10M
-55
100M
RL = 100 Ω
Figure 18. CMRR, PSRR, ROUT
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Typical Characteristics (continued)
TA = 25°C, VS = ±5 V, RL = 100 Ω, Rf = 237 Ω (unless otherwise noted)
120
220
110
200
100
180
90
160
0.006
0.03
0.004
0.02
70
120
60
100
PHASE
50
60
30
40
20
100k
1M
10M
100M
-0.002
DG
-0.004
-0.02
20
10k
0
0
-0.01
80
40
0.002
0.01
-0.03
-1.5 -1.2 -0.9 -0.6 -0.3 0
1G
Frequency (Hz)
VS = ±5 V
DP (°)
140
DG (%)
MAG
80
Phase (°)
Gain (dB)
DP
-0.006
0.3 0.6 0.9 1.2 1.5
VOUT (V)
RL = 100 Ω
RF = 237 Ω
Figure 19. Transimpedance
RL = 150 Ω
Figure 20. DG/DP (NTSC)
0.009
0.03
0.006
0.02
DP
0.003
0
0
-0.003
-0.01
-0.02
DP (°)
DG (%)
0.01
DG
-0.03
-1.5 -1.2 -0.9 -0.6 -0.3 0
-0.006
-0.009
0.3 0.6 0.9 1.2 1.5
VOUT (V)
RF = 237 Ω
RL = 150 Ω
Figure 21. DG/DP (PAL)
10
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7 Detailed Description
7.1 Overview
The LMH6702-MIL has been optimized for exceptionally low harmonic distortion while driving very demanding
resistive or capacitive loads. Generally, when used as the input amplifier to very high speed flash ADCs, the
distortions introduced by the converter will dominate over the low LMH6702-MIL distortions shown in Typical
Characteristics.
7.2 Feature Description
7.2.1 Harmonic Distortion
The capacitor CSS, shown across the supplies in Figure 24 and Figure 25, is critical to achieving the lowest 2nd
harmonic distortion. For absolute minimum distortion levels, it is also advisable to keep the supply decoupling
currents (ground connections to CPOS, and CNEG in Figure 24 and Figure 25) separate from the ground
connections to sensitive input circuitry (such as RG, RT, and RIN ground connections). Splitting the ground plane
in this fashion and separately routing the high frequency current spikes on the decoupling caps back to the
power supply (similar to Star Connection layout technique) ensures minimum coupling back to the input circuitry
and results in best harmonic distortion response (especially 2nd order distortion).
If this layout technique has not been observed on a particular application board, designer may actually find that
supply decoupling caps could adversely affect HD2 performance by increasing the coupling phenomenon already
mentioned. Figure 22 shows actual HD2 data on a board where the ground plane is shared between the supply
decoupling capacitors and the rest of the circuit. Once these capacitors are removed, the HD2 distortion levels
reduce significantly, especially between 10 MHz to 20 MHz, as shown in Figure 22:
-30
-40
CPOS & CNEG
INCLUDED
HD2 (dBc)
-50
-60
CPOS & CNEG
REMOVED
-70
-80
-90
1
10
Frequency (MHz)
100
Figure 22. Decoupling Current Adverse Effect on a Board with Shared Ground Plane
At these extremely low distortion levels, the high frequency behavior of decoupling capacitors themselves could
be significant. In general, lower value decoupling caps tend to have higher resonance frequencies making them
more effective for higher frequency regions. A particular application board which has been laid out correctly with
ground returns split to minimize coupling, would benefit the most by having low value and higher value capacitors
paralleled to take advantage of the effective bandwidth of each and extend low distortion frequency range.
Another important variable in getting the highest fidelity signal from the LMH6702-MIL is the package itself. As
already noted, coupling between high frequency current transients on supply lines and the device input can lead
to excess harmonic distortion. An important source of this coupling is in fact through the device bonding wires. A
smaller package, in general, will have shorter bonding wires and therefore lower coupling. This is true in the case
of the SOT-23 compared to the SOIC package where a marked improvement in HD can be measured in the
SOT-23 package. Figure 23 shows the HD comparing SOT-23 to SOIC package:
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Feature Description (continued)
-60
HD2, SOIC
-65
-70
HD2 (dBc)
-75
HD2, SOT23
-80
-85
-90
HD3, SOIC
-95
HD3, SOT23
-100
-105
-110
1
10
Frequency (MHz)
100
Figure 23. SOIC and SOT-23 Packages Distortion Terms Compared
The LMH6702-MIL data sheet shows both SOT-23 and SOIC data in Electrical Characteristics to aid in selecting
the right package. Typical Characteristics shows SOIC package plots only.
7.3 Device Functional Modes
7.3.1 2-Tone 3rd Order Intermodulation
Figure 10 shows a relatively constant difference between the test power level and the spurious level with the
difference depending on frequency. The LMH6702-MIL does not show an intercept type performance, (where the
relative spurious levels change at a 2X rate versus the test tone powers), due to an internal full power bandwidth
enhancement circuit that boosts the performance as the output swing increases while dissipating negligible
quiescent power under low output power conditions. This feature enhances the distortion performance and full
power bandwidth to match that of much higher quiescent supply current parts.
7.3.2 DC Accuracy and Noise
The example in Equation 1 shows the output offset computation equation for the non-inverting configuration
using the typical bias current and offset specifications for AV = 2:
Output Offset:
VO = (±IBN · RIN ± VIO) (1 + RF/RG) ± IBI · RF
where
•
RIN is the equivalent input impedance on the non-inverting input.
(1)
Example computation for AV = +2, RF = 237Ω, RIN = 25Ω:
VO = (±6 μA × 25 Ω ± 1mV) (1 + 237/237) ± 8 μA × 237 = ±4.20 mV
(2)
A good design, however, should include a worst case calculation using min/max numbers in the data sheet
tables, in order to ensure worst case operation.
Further improvement in the output offset voltage and drift is possible using the composite amplifiers described in
Application Note OA--07, Current Feedback Op Amp Applications Circuit Guide (SNOA365). The two input bias
currents are physically unrelated in both magnitude and polarity for the current feedback topology. It is not
possible, therefore, to cancel their effects by matching the source impedance for the two inputs (as is commonly
done for matched input bias current devices).
The total output noise is computed in a similar fashion to the output offset voltage. Using the input noise voltage
and the two input noise currents, the output noise is developed through the same gain equations for each term
but combined as the square root of the sum of squared contributing elements. See Application Note OA-12,
Noise Analysis for Comlinear Amplifiers (SNOA375) for a full discussion of noise calculations for current
feedback amplifiers.
12
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LMH6702-MIL achieves its excellent pulse and distortion performance by using the current feedback
topology. The loop gain for a current feedback op amp, and hence the frequency response, is predominantly set
by the feedback resistor value. The LMH6702-MIL is optimized for use with a 237-Ω feedback resistor. Using
lower values can lead to excessive ringing in the pulse response while a higher value will limit the bandwidth.
8.2 Typical Application
8.2.1 Feedback Resistor
The LMH6702-MIL achieves its excellent pulse and distortion performance by using the current feedback
topology. The loop gain for a current feedback op amp, and hence the frequency response, is predominantly set
by the feedback resistor value. The LMH6702-MIL is optimized for use with a 237-Ω feedback resistor. Using
lower values can lead to excessive ringing in the pulse response while a higher value will limit the bandwidth.
+5V
6.8µF
AV = 1 +RF/RG = VOUT/VIN
.01µF
VIN
7 CPOS
3
CSS
0.1µF
RIN
+
VOUT
6
LMH6702MIL
2
4 CNEG
RF
.01µF
RG
6.8µF
-5V
Copyright © 2017, Texas Instruments Incorporated
Figure 24. Recommended Non-Inverting Gain Circuit
+5V
6.8µF
RF
.01µF
25:
RG
=
VOUT
VIN
7 CPOS
3
CSS
0.1µF
AV =
+
LMH6702MIL
VOUT
6
2
VIN
RG
4 CNEG
.01µF
RT
6.8µF
-5V
RF
SELECT RT TO
YIELD DESIRED
RIN = RT||RG
Copyright © 2017, Texas Instruments Incorporated
Figure 25. Recommended Inverting Gain Circuit
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Typical Application (continued)
8.2.2 Design Requirements
The exceptional performance and uniquely targeted superior technical specifications of the LMH6702-MIL make
it a natural choice for high speed data acquisition applications as a front end amplifier driving the input of a high
performance ADC. Of these specifications, the following can be discussed in more detail:
1. A bandwidth of 1.7 GHz and relative insensitivity of bandwidth to closed loop gain (characteristic of Current
Feedback architecture when compared to the traditional voltage feedback architecture) as shown in Figure 1.
2. Ultra-low distortion approaching -87 dBc at the lower frequencies and exceptional noise performance (see
Figure 9 and Figure 17).
3. Fast settling in less than 20 ns (see Figure 27).
As the input of an ADC could be capacitive in nature and could also alternate in capacitance value during a
typical acquisition cycle, the driver amplifier (LMH6702-MIL in this case) should be designed so that it avoids
instability, peaking, or other undesirable artifacts.
For Capacitive Load Drive, see Figure 26, which shows a typical application using the LMH6702-MIL to drive an
ADC.
ADC
+
RS
LMH6702MIL
-
CIN
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Figure 26. Input Amplifier to ADC
8.2.3 Detailed Design Procedure
The series resistor, RS, between the amplifier output and the ADC input is critical to achieving best system
performance. This load capacitance, if applied directly to the output pin, can quickly lead to unacceptable levels
of ringing in the pulse response. Figure 27 in Application Curve (RS and Settling Time vs CL) is an excellent
starting point for selecting RS. The value derived in that plot minimizes the step settling time into a fixed discrete
capacitive load with the output driving a very light resistive load (1 kΩ). Sensitivity to capacitive loading is greatly
reduced once the output is loaded more heavily. Therefore, for cases where the output is heavily loaded, RS
value may be reduced. The exact value may best be determined experimentally for these cases.
In applications where the LMH6702-MIL is replacing the CLC409, care must be taken when the device is lightly
loaded and some capacitance is present at the output. Due to the much higher frequency response of the
LMH6702-MIL compared to the CLC409, there could be increased susceptibility to low value output capacitance
(parasitic or inherent to the board layout or otherwise being part of the output load). As already mentioned, this
susceptibility is most noticeable when the LMH6702-MIL's resistive load is light. Parasitic capacitance can be
minimized by careful lay out. Addition of an output snubber R-C network will also help by increasing the high
frequency resistive loading.
Referring back to Figure 26, it must be noted that several additional constraints should be considered in driving
the capacitive input of an ADC. There is an option to increase RS, band-limiting at the ADC input for either noise
or Nyquist band-limiting purposes. However, increasing RS too much can induce an unacceptably large input
glitch due to switching transients coupling through from the convert signal. Also, CIN is oftentimes a voltage
dependent capacitance. This input impedance non-linearity will induce distortion terms that will increase as RS is
increased. Only slight adjustments up or down from the recommended RS value should therefore be attempted in
optimizing system performance.
14
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Typical Application (continued)
8.2.4 Application Curve
100
25
0.05% SETTLING
90
80
RS (:)
60
15
50
0.1% SETTLING
40
RS
10
30
20
Settling Time (ns)
20
70
5
10
0
1
10
100
1k
0
10k
CL (pF)
AV = -1
RL = 1 kΩ
Figure 27. RS and Settling Time vs CL
9 Power Supply Recommendations
The LMH6702-MIL can operate off a single supply or with dual supplies as long as the input CM voltage range
(CMIR) has the required headroom to either supply rail. Supplies should be decoupled with low inductance, often
ceramic, capacitors to ground less than 0.5 inches from the device pins. The use of ground plane is
recommended, and as in most high speed devices, it is advisable to remove ground plane close to device
sensitive pins such as the inputs.
10 Layout
10.1 Layout Guidelines
Generally, a good high frequency layout will keep power supply and ground traces away from the inverting input
and output pins. Parasitic capacitances on these nodes to ground will cause frequency response peaking and
possible circuit oscillations. See Frequent Faux Pas in Applying Wideband Current Feedback Amplifiers,
Application Note OA-15 (SNOA367). Texas Instruments suggests the following evaluation boards as a guide for
high frequency layout and as an aid in device testing and characterization. See Table 1 for details.
The LMH6702-MIL evaluation board(s) is a good example of high frequency layout techniques as a reference.
General high-speed, signal-path layout suggestions include:
• Continuous ground planes are preferred for signal routing with matched impedance traces for longer runs.
However, open up both ground and power planes around the capacitive sensitive input and output device
pins as shown in Figure 28. After the signal is sent into a resistor, parasitic capacitance becomes more of a
bandlimiting issue and less of a stability issue.
• Use good, high-frequency decoupling capacitors (0.1 μF) on the ground plane at the device power pins as
shown in Figure 28. Higher value capacitors (2.2 μF) are required, but may be placed further from the device
power pins and shared among devices. For best high-frequency decoupling, consider X2Y supply-decoupling
capacitors that offer a much higher self-resonance frequency over standard capacitors.
• When using differential signal routing over any appreciable distance, use microstrip layout techniques with
matched impedance traces.
• The input summing junction is very sensitive to parasitic capacitance. Connect any Rf, and Rg elements into
the summing junction with minimal trace length to the device pin side of the resistor, as shown in Figure 29.
The other side of these elements can have more trace length if needed to the source or to ground.
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10.2 Layout Example
Figure 28. LMH6702-MIL Evaluation Board Layer 1
Figure 29. LMH6702-MIL Evaluation Board Layer 2
Table 1. Evaluation Board Comparison
16
DEVICE
PACKAGE
EVALUATION BOARD PART NUMBER
LMH6702-MILMF
SOT-23
LMH730216
LMH6702-MILMA
SOIC
LMH730227
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11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For related documentation, see the following:
• Absolute Maximum Ratings for Soldering (SNOA549)
• Current Feedback Op Amp Applications Circuit Guide, Application Note OA--07 (SNOA365)
• Frequent Faux Pas in Applying Wideband Current Feedback Amplifiers, Application Note OA-15 (SNOA367)
• Noise Analysis for Comlinear Amplifiers, Application Note OA-12 (SNOA375)
• Semiconductor and IC Package Thermal Metrics (SPRA953)
11.2 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.3 Trademarks
VIP10, E2E are trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
11.4 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
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29-Jun-2017
PACKAGING INFORMATION
Orderable Device
Status
(1)
LMH6702 MDC
ACTIVE
Package Type Package Pins Package
Drawing
Qty
DIESALE
Y
0
754
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Green (RoHS
& no Sb/Br)
Call TI
Level-1-NA-UNLIM
Op Temp (°C)
Device Marking
(4/5)
-40 to 85
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
Samples
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