NSC LMH6734MQ Single supply, ultra high-speed, triple selectable gain buffer Datasheet

LMH6734
Single Supply, Ultra High-Speed, Triple Selectable Gain
Buffer
General Description
Features
The LMH6734 is a high speed monolithic selectable gain
buffer designed specifically for ultra high resolution video systems as well as wide dynamic range systems requiring exceptional signal fidelity. Benefiting from National's current
feedback architecture, the LMH6734 offers gains of −1, +1
and +2. At a gain of +2 the LMH6734 supports ultra high resolution video systems with a 560 MHz 2 VPP
3 dB bandwidth. With this large signal bandwidth and 2.1 nV/
of input referred noise, the LMH6734 is ideal for driving
component video over CAT5 cable up to 200 ft without frequency and gain equalization. The LMH6734 is offered in a
space saving 16-Pin SSOP package.
(Typical values unless otherwise specified.)
■ Supply range 3V to 12V single supply
■ Supply range ±1.5V to ±6V split supply
■ 925 MHz −3 dB small signal bandwidth (AV = +1, VS = ±5V)
■ 650 MHz −3 dB small signal bandwidth (AV = +2, VS = 5V)
■ Low supply current (5.5 mA per op amp, VS = 5V)
■ 2.1 nV/√Hz input noise voltage
■ 3750 V/μs slew rate (VS = ±5V)
■ 70 mA linear output current (AV = +2, VS = ±5V)
■ Input range and output swing to 1V from each supply rail
Applications
■
■
■
■
■
■
■
HDTV component video driver
CAT5 component video driver
High resolution projectors
Wide dynamic range IF amp
DDS post-amps
Wideband inverting summer
Line driver
Connection Diagram
16-Pin SSOP
30003610
Top View
RF = RG = 327Ω
VIP10™ is a trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation
300036
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LMH6734 Single Supply, Ultra High Speed, Triple Selectable Gain Buffer
September 2007
LMH6734
Soldering Information
Infrared or Convection (20 sec.)
Wave Soldering (10 sec.)
Storage Temperature Range
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Tolerance (Note 5)
Human Body Model
Machine Model
Supply Voltage (V+ - V–)
IOUT
Common Mode Input Voltage
Maximum Junction Temperature
Storage Temperature Range
Operating Ratings
2000V
200V
13.2V
(Note 4)
±VCC
+150°C
−65°C to +150°C
5V Electrical Characteristics
235°C
260°C
−65°C to +150°C
(Note 1)
Temperature Range (Note 3)
Supply Voltage (V+ - V–)
Thermal Resistance
Package
−40°C to +85°C
3V to 12V
(θJC)
36°C/W
16-Pin SSOP
(θJA)
120°C/W
(Note 2)
Unless otherwise specified, all limits are guaranteed for TA = 25°C, V+ = +5V, AV = +2, RL = 100Ω. Boldface limits apply at the
temperature extremes.
Symbol
Parameter
Conditions
Min
(Note 8)
Typ
(Note 7)
Max
(Note 8)
Units
Frequency Domain Performance
UGBW
−3 dB Bandwidth
Unity Gain, VOUT = 200 mVPP
870
SSBW
−3 dB Bandwidth
VOUT = 200 mVPP, RL = 100Ω
650
SSBW
VOUT = 200 mVPP, RL = 150Ω
685
LSBW
VOUT = 2 VPP
480
0.1 dB BW 0.1 dB Gain Flatness
VOUT = 200 mVPP
130
MHz
MHz
MHz
Time Domain Response
TRS
Rise and Fall Time
(10% to 90%)
2V Step
0.7
ns
SR
Slew Rate
2V Step
1900
V/µs
ts
Settling Time to 0.1%
2V Step
10
ns
te
Enable Time
From Disable = Rising Edge
10
ns
td
Disable Time
From Disable = Falling Edge
15
ns
HD2L
2nd Harmonic Distortion
2 VPP, 10 MHz
−63
dBc
HD3L
3rd Harmonic Distortion
2 VPP, 10 MHz
−73
dBc
Distortion
Equivalent Input Noise
VN
Non-Inverting Voltage
>10 MHz
2.1
nV/
ICN
Inverting Current
>10 MHz
18.6
pA/
NCN
Non-Inverting Current
>10 MHz
26.9
pA/
Video Performance
DG
Differential Gain
4.43 MHz, RL = 150Ω
0.03
%
DP
Differential Phase
4.43 MHz, RL = 150Ω
0.025
deg
Static, DC Performance
VIO
Input Offset Voltage
IBN
Input Bias Current
Non-Inverting
PSRR
Power Supply Rejection Ratio
CMRR
0.4
2.0
2.5
mV
2
16.7
28
32
µA
+PSRR
59
59
61
−PSRR
58
56
61
52
52
54.5
Common Mode Rejection Ratio
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2
dB
dB
Parameter
Conditions
XTLK
Crosstalk
Input Referred, f = 10 MHz, Drive
Channels A, C and Measure
Channel B
ICC
Supply Current
All three amps Enabled, No Load
Min
(Note 8)
Typ
(Note 7)
Max
(Note 8)
−80
15
15
Units
dB
16.7
18
19
mA
Supply Current Disabled V+
RL = ∞
1.54
1.8
mA
V−
RL = ∞
0.75
1.8
mA
%
Supply Current Disabled
Gain Error
RL = ∞
Gain
AV = +2
0.2
1.25
1.975
1.996
2.025
−0.9875
−0.998
AV = +1
0.998
AV = −1
V/V
−1.0125
Miscellaneous Performance
RIN+
Non-Inverting Input Resistance
200
CIN+
Non-Inverting Input Capacitance
kΩ
1
RO
Output Impedance
DC
pF
0.05
VO
Output Voltage Range
RL = 100Ω
1.25-3.75
1.3-3.7
1.12-3.88
Ω
RL = ∞
1.11-3.89
1.15-3.85
1.03-3.97
V
CMIR
Input Range
Driving input +INA, CMRR > 40 dB
1.1-3.9
1.2-3.8
1.0-4.0
IO
Linear Output Current
VIN = 0V, VOUT < ±42 mV (Note 4)
±50
±60
mA
ISC
Short Circuit Current
VIN = 2V Output Shorted to Ground
(Note 6)
170
mA
IIH
Disable Pin Bias Current High
Disable Pin = V+
−72
μA
IIL
Disable Pin Bias Current Low
Disable Pin = 0V
−360
μA
VDMAX
Voltage for Disable
Disable Pin ≤ VDMAX
3.2
V
VDMIM
Voltage for Enable
Disable Pin ≥ VDMIN
3.6
V
±5V Electrical Characteristics
V
(Note 2)
Unless otherwise specified, all limits are guaranteed for TA = 25°C, V+ = +5V, V− = −5V, AV = +2, RL = 100Ω. Boldface limits apply
at the temperature extremes.
Symbol
Parameter
Conditions
Min
(Note 8)
Typ
(Note 7)
Max
(Note 8)
Units
Frequency Domain Performance
UGBW
−3 dB Bandwidth
Unity Gain, VOUT = 200 mVPP
925
SSBW
−3 dB Bandwidth
VOUT = 200 mVPP, RL = 100Ω
730
SSBW
VOUT = 200 mVPP, RL = 150Ω
760
LSBW
VOUT = 2 VPP
560
0.1 dB BW 0.1 dB Gain Flatness
VOUT = 200 mVPP
270
MHz
MHz
MHz
Time Domain Response
TRS
Rise and Fall Time
(10% to 90%)
2V Step
0.7
TRL
5V Step
0.8
SR
Slew Rate
2V Step
3750
V/µs
ts
Settling Time to 0.1%
2V Step
10
ns
te
Enable Time
From Disable = Rising Edge
10
ns
td
Disable Time
From Disable = Falling Edge
15
ns
3
ns
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LMH6734
Symbol
LMH6734
Symbol
Parameter
Conditions
Min
(Note 8)
Typ
(Note 7)
Max
(Note 8)
Units
Distortion
HD2L
2nd Harmonic Distortion
2 VPP, 10 MHz
−72
dBc
HD3L
3rd Harmonic Distortion
2 VPP, 10 MHz
−63
dBc
Equivalent Input Noise
VN
Non-Inverting Voltage
>10 MHz
2.1
nV/
ICN
Inverting Current
>10 MHz
18.6
pA/
NCN
Non-Inverting Current
>10 MHz
26.9
pA/
Video Performance
DG
Differential Gain
4.43 MHz, RL = 150Ω
0.03
%
DP
Differential Phase
4.43 MHz, RL = 150Ω
0.03
deg
Static, DC Performance
VIO
Input Offset Voltage
0.6
2.4
3.4
mV
IBN
Input Bias Current
Non-Inverting
−14
−19
3.5
19
24
µA
PSRR
Power Supply Rejection Ratio
+PSRR
59
59
61.5
−PSRR
58
58
61
53
53
55
CMRR
Common Mode Rejection Ratio
XTLK
Crosstalk
Input Referred, f = 10 MHz, Drive
Channels A, C and Measure
Channel B
ICC
Supply Current
All three amps Enabled, No Load
Supply Current Disabled V+
dB
dB
−80
18
18
dB
19.5
20.8
22
mA
RL = ∞
1.54
1.8
mA
Supply Current Disabled V−
RL = ∞
0.75
1.8
mA
Gain Error
RL = ∞
0.2
1.25
%
Gain
AV = +2
1.996
2.025
1.975
AV = +1
0.998
AV = −1
−0.9875
−0.998
V/V
−1.0125
Miscellaneous Performance
RIN+
Non-Inverting Input Resistance
CIN+
Non-Inverting Input Capacitance
200
kΩ
1
pF
RO
Output Impedance
DC
VO
Output Voltage Range
RL = 100Ω
±3.55
±3.5
±3.7
0.05
Ω
±4.0
V
RL = ∞
±3.85
CMIR
Input Range
Driving input +INA, CMRR > 40 dB
±3.9
±3.8
±4.0
IO
Linear Output Current
VIN = 0V, VOUT < ±43 mV (Note 4)
70
±80
mA
ISC
Short Circuit Current
VIN = 2V Output Shorted to Ground
(Note 6)
237
mA
IIH
Disable Pin Bias Current High
Disable Pin = V+
−72
μA
IIL
Disable Pin Bias Current Low
Disable Pin = 0V
−360
μA
VDMAX
Voltage for Disable
Disable Pin ≤ VDMAX
3.2
V
VDMIM
Voltage for Enable
Disable Pin ≥ VDMIN
3.6
V
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4
V
Note 2: 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. See Applications Information for information on temperature de-rating of this device. Min/Max ratings are based on product characterization and simulation.
Individual parameters are tested as noted.
Note 3: The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is
PD = (TJ(MAX) - TA) / θJA. All numbers apply for packages soldered directly onto a PC Board.
Note 4: The maximum output current (IOUT) is determined by device power dissipation limitations. See the Power Dissipation section of the Application Information
for more details.
Note 5: Human Body Model, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC
Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC).
Note 6: Short circuit current should be limited in duration to no more than 10 seconds. See the Power Dissipation section of the Application Information for more
details.
Note 7: Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will
also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material.
Note 8: Limits are 100% production tested at 25C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control
(SQC) methods.
Ordering Information
Package
16-Pin SSOP
Part Number
LMH6734MQ
LMH6734MQX
Package Marking
LH6734MQ
5
Transport Media
95 Units/Rail
2.5k Units Tape and Reel
NSC Drawing
MQA16
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LMH6734
Note 1: 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 guaranteed. For guaranteed specifications, see the Electrical Characteristics tables.
LMH6734
Typical Performance Characteristics V+ = +5V
(TA = 25°C, AV = +2, RL = 100Ω, unless otherwise
specified.)
Large Signal Frequency Response
Small Signal Frequency Response
30003631
30003632
Small Signal Frequency Response
Frequency Response vs. VOUT
30003664
30003601
Frequency Response vs. Supply Voltage
Gain Flatness
30003662
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30003647
6
LMH6734
Gain Flatness, Dual Input Buffer
Pulse Response
30003648
30003622
Crosstalk vs. Frequency
Distortion vs. Frequency
30003635
30003633
Distortion vs. Output Voltage
Small Signal Frequency Response vs. Resistive Load
30003634
30003661
7
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LMH6734
Frequency Response vs. Capacitive Load
Series Output Resistance vs. Capacitive Load
30003614
30003619
PSRR vs. Frequency
Open Loop Gain and Phase
30003621
30003626
Closed Loop Output Impedance |Z|
Disable Timing
30003624
30003604
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Channel to Channel Crosstalk vs. Frequency
30003649
30003660
Disabled Channel Isolation vs. Frequency
30003663
Typical Performance Characteristics V+ = +5V, V− = −5V
(TA = 25°C, AV = +2, RL = 100Ω,
unless otherwise specified.)
Large Signal Frequency Response
Small Signal Frequency Response
30003651
30003652
9
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LMH6734
DC Errors vs. Temperature
LMH6734
Frequency Response vs. VOUT
Frequency Response vs. Supply Voltage
30003653
30003616
Gain Flatness
Gain Flatness, Dual Input Buffer
30003655
30003654
Pulse Response
Pulse Response
30003657
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30003658
10
LMH6734
Distortion vs. Frequency
Distortion vs. Output Voltage
30003646
30003645
DC Errors vs. Temperature
Crosstalk vs. Frequency
30003656
30003659
11
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LMH6734
Application Information
GENERAL INFORMATION
The LMH6734 is a high speed current feedback selectable
gain buffer (SGB), optimized for very high speed applications.
With its internal feedback and gain-setting resistors,
RF = RG = 327Ω, the LMH6734 offers excellent AC performance while simplifying board layout and minimizing the
effects of layout related parasitic components. The LMH6734
has no internal ground reference so single or split supply configurations are both equally useful.
SETTING THE CLOSED LOOP GAIN
The LMH6734 can be configured with gain settings of
AV = +2, +1, or −1. Table 1, shows the non-inverting and inverting pin connections to achieve the desired closed loop
gain.
Table 1. Setting the Closed Loop
Gain
GAIN AV
30003608
INPUT CONNECTIONS
Non-Inverting
Inverting
−1 V/V
Ground
Input Signal
+1 V/V
Input Signal
NC (Open)
+2 V/V
Input Signal
Ground
FIGURE 2. Recommended Split Supply Non-Inverting
Gain Circuit, Gain +1 V/V
SPLIT SUPPLY APPLICATION
The recommended split supply circuit applications are shown
in Figure 1, Figure 2 , and Figure 3. In all three configurations
the input signal is DC coupled with a termination resister input
RIN = 50Ω. In Figure 1 the inverting input is connected to
ground completing the internal feedback loop to set the gain
to +2 V/V. In Figure 2 the inverting input is open (no-connect),
thus providing a buffer configuration of +1 V/V. Figure 3
shows a buffer configuration with a gain of −1 V/V. In this
configuration an input resistor of 59Ω was used to balance the
internal RG resistor of 327Ω and to provide a 50Ω termination.
30003603
FIGURE 3. Recommended Split Supply Inverting Gain
Circuit, Gain = –1 V/V
SINGLE SUPPLY APPLICATION
The LMH6734 can also be configured for single supply applications as shown in Figure 4, Figure 5, and Figure 6. In Figure
4, the 220 μF capacitor was chosen to satisfy low frequency
input signals and to provide an open for the internal feedback
network path, thus setting the gain to +1 V/V. With an AC signal present, this 220 μF capacitor is shunted to ground and
completes the feedback resistor network to set the AC coupled gain of +2 V/V. The input is AC coupled with the 22 μF
capacitor and the two 4.7 kΩ resistors to set the input DC bias
voltage. Figure 5 shows the single supply buffer configuration
with the inverting input open (no-connect) creating an open to
the internal feedback network giving a gain of +1 V/V. The
input voltage is AC coupled with the 22 μF capacitor along
with two 4.7 kΩ resistors to set the input DC bias voltage.
Figure 6 shows the single supply buffer configuration for a
gain of −1 V/V. In this circuit, the input signal is DC coupled
into the inverting input closing the internal feedback network
and creating a gain of −1 V/V while an AC gain of +2 V/V is
present at the non-inverting input. Thus, the 6.8 kΩ and the
30003605
FIGURE 1. Recommended Split Supply Non-Inverting
Gain Circuit, Gain = +2 V/V
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UNITY GAIN COMPENSATION
With a current feedback Selectable Gain Buffer like the
LMH6734, the feedback resistor is a compromise between
the value needed for stability at unity gain and the optimized
value used at a gain of two. The result of this compromise is
substantial peaking at unity gain. If this peaking is undesirable
a simple RC filter at the input of the buffer will smooth the
frequency response as shown in Figure 7. Figure 8 shows the
results of a simple filter placed on the non-inverting input. See
Figure 9 and Figure 10 for another method of reducing unity
gain peaking.
30003642
30003630
FIGURE 4. Recommended Single Supply Non-Inverting
Gain Circuit, Gain = +2 V/V
FIGURE 7. Correction for Unity Gain Peaking
30003644
FIGURE 5. Recommended Single Supply Non-Inverting
Gain Circuit, Gain = +1 V/V
30003629
FIGURE 8. Frequency Response for Circuit in Figure 7
30003643
FIGURE 6. Recommended Single Supply Inverting Gain
Circuit, Gain = −1 V/V
30003607
The gain of the LMH6734 is accurate to ±1% and stable over
temperature. The internal gain setting resistors, RF and RG,
match very well. However, over process and temperature
their absolute value will change. Using external resistors in
series with RG to change the gain will result in poor gain accuracy over temperature and from part to part.
FIGURE 9. Alternate Unity Gain Compensation
13
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LMH6734
2.2 kΩ resistors were chosen to set the input DC bias voltage
to 1/4 the supply voltage such that at high frequencies the
output voltage is gained up by +2 V/V.
LMH6734
30003637
FIGURE 10. Frequency Response for Circuit in Figure 9 (Standard Circuit Figure 5)
COMPONENT DRIVER
The LMH6734 is capable of transmitting and receiving component video over short to moderate unshielded twisted-pair
(UTP) CAT5 cables, as shown in Figure 11. The component
signals Y, Pb, and Pr are connected to the LMH6734 transmit
side inputs with a 75Ω termination. The LMH6734 transmit
amplifiers are configured for a gain of +2 V/V before driving
the CAT5 cable. Only three out of the four pairs in the standard CAT5 are utilized, the fourth pair is available for audio.
The output of the LMH6734 transmit amplifier drives a 50Ω
transmission system with one side of the twisted pair terminated 50Ω to ground. Note this system, without signal equalization, will satisfy transmission up to 200 ft. For longer cable
lengths, frequency and gain equalization to compensate for
signal degradation is recommended.
The LMH6734 receive side is configured for a unity gain buffer
for the component signals received through the CAT5 cable.
The inputs of the receiver channels are 100Ω differentially
terminated. The two 327Ω external resisters were chosen to
match the internal RF and RG value of 327Ω. Figure 12, shows
the LMH6734 transceiver frequency response over various
lengths of CAT5 cable with a 1 VPP input signal at ±5 supply
voltage. The CMRR of the LMH6734 receive side at low frequencies is 55 dB at best with a split power supply of ±5V.
30003665
FIGURE 11. Component Video Transmission Over UTP (CAT5)
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14
LMH6734
30003666
FIGURE 12. Frequency Response vs. Normalized Gain and CAT5 Cable Length
grade second order harmonic performance, especially if the
supply traces are thin and /or long. In Figure 1, Figure 2, and
Figure 3 it is recommended an optional capacitor, CSS= 0.01
μF, be connected between the split supplies for best second
harmonic distortion. Another option to using CSS is to use
pairs of 0.01 μF and 0.1 μF ceramic capacitors for each supply
bypass.
DRIVING CAPACITIVE LOADS
Capacitive output loading applications will benefit from the
use of a series output resistor ROUT. Figure 13 shows the use
of a series output resistor, ROUT, to stabilize the amplifier output under capacitive loading. Capacitive loads of 5 to 120 pF
are the most critical, causing ringing, frequency response
peaking and possible oscillation. The charts “Suggested
ROUT vs. Cap Load” give a recommended value for selecting
a series output resistor for mitigating capacitive loads. The
values suggested in the charts are selected for 0.5 dB or less
of peaking in the frequency response. This gives a good compromise between settling time and bandwidth. For applications where maximum frequency response is needed and
some peaking is tolerable, the value of ROUT can be reduced
slightly from the recommended values.
VIDEO PERFORMANCE
The LMH6734 has been designed to provide excellent performance with production quality video signals in a wide variety of formats such as HDTV and High Resolution VGA.
NTSC and PAL performance is nearly flawless. Best performance will be obtained with back terminated loads. The back
termination reduces reflections from the transmission line and
effectively masks transmission line and other parasitic capacitances from the amplifier output stage. Figure 7 shows a
typical configuration for driving a 75Ω cable. The amplifier is
configured for a gain of two to make up for the 6 dB of loss in
ROUT.
POWER DISSIPATION
The LMH6734 is optimized for maximum speed and performance in the small form factor of the standard 16-Pin SSOP
package. To achieve its high level of performance, the
LMH6734 consumes an appreciable amount of quiescent
current which cannot be neglected when considering the total
package power dissipation limit. The quiescent current contributes to about 40° C rise in junction temperature when no
additional heat sink is used (VS = ±5V, all three channels on).
Therefore, it is easy to see the need for proper precautions in
order to make sure the junction temperature’s absolute maximum rating of 150°C is not violated.
To ensure maximum output drive and highest performance,
thermal shutdown is not provided. Therefore, it is of utmost
importance to make sure that the TJMAX is never exceeded
due to the overall power dissipation (all three channels).
With the LMH6734 used in a back-terminated 75Ω RGB analog video system (with 2 VPP output voltage), the total power
dissipation is around 305 mW of which 220 mW is due to the
quiescent device dissipation (output black level at 0V). With
no additional heat sink used, the junction temperature rises
to about 120°C when operated at 85°C ambient.
To reduce the junction temperature many options are available. Forced air cooling is the easiest option. An external add-
30003638
FIGURE 13. Decoupling Capacitive Loads
LAYOUT CONSIDERATIONS
Whenever questions about layout arise, use the evaluation
board as a guide. The LMH730275 is the evaluation board
supplied with samples of the LMH6734.
To reduce parasitic capacitances, ground and power planes
should be removed near the input and output pins. For long
signal paths controlled impedance lines should be used,
along with impedance matching elements at both ends.
Bypass capacitors should be placed as close to the device as
possible. Bypass capacitors from each rail to ground are applied in pairs. The larger electrolytic bypass capacitors can be
located farther from the device, the smaller ceramic capacitors should be placed as close to the device as possible. The
LMH6734 has multiple power and ground pins for enhanced
supply bypassing. Every pin should ideally have a separate
bypass capacitor. Sharing bypass capacitors may slightly de15
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LMH6734
on heat-sink can be added to the 16-Pin SSOP package, or
alternatively, additional board metal (copper) area can be utilized as heat-sink.
An effective way to reduce the junction temperature for the
16-Pin SSOP package (and other plastic packages) is to use
the copper board area to conduct heat. With no enhancement
the major heat flow path in this package is from the die
through the metal lead frame (inside the package) and onto
the surrounding copper through the interconnecting leads.
Since high frequency performance requires limited metal near
the device pins the best way to use board copper to remove
heat is through the bottom of the package. A gap filler with
high thermal conductivity can be used to conduct heat from
the bottom of the package to copper on the circuit board. Vias
to a ground or power plane on the back side of the circuit
board will provide additional heat dissipation. A combination
of front side copper and vias to the back side can be combined
as well.
Follow these steps to determine the maximum power dissipation for the LMH6734:
1. Calculate the quiescent (no-load) power: PAMP = ICC X
(VS) VS = V+-V−
2. Calculate the RMS power dissipated in the output stage:
PD (rms) = rms ((VS - VOUT) X IOUT) where VOUT and
IOUT are the voltage and current across the external load
and VS is the total supply current
3. Calculate the total RMS power: PT = PAMP+PD
The maximum power that the LMH6734 package can dissipate at a given temperature (See Figure 14) can be derived
with the following equation:
PMAX = (150° C/W – TAMB)/ θJA, where TAMB = Ambient temperature (°C) and θJA = Thermal resistance, from junction to
ambient, for a given package (°C/W). For the SSOP package
θJA is 120°C/W.
ESD PROTECTION
The LMH6734 is protected against electrostatic discharge
(ESD) on all pins. The LMH6734 will survive 2000V Human
Body Model and 200V Machine Model events.
Under closed loop operation the ESD diodes have no affect
on circuit performance. There are occasions, however, when
the ESD diodes will be evident. If the LMH6734 is driven by
a large signal while the device is powered down the ESD
diodes will conduct.
The current that flows through the ESD diodes will either exit
the chip through the supply pins or will flow through the device, hence it is possible to power up a chip with a large signal
applied to the input pins. Shorting the power pins to each other
will prevent the chip from being powered up through the input.
EVALUATION BOARDS
National Semiconductor provides the following evaluation
boards as a guide for high frequency layout and as an aid in
device testing and characterization. Many of the datasheet
plots were measured with these boards.
Device
Package Evaluation Board Part Number
LMH6734MQ SSOP
LMH730275
A bare evaluation board can be ordered when a sample request is placed with National Semiconductor.
30003602
FIGURE 14. Maximum Power Dissipation
www.national.com
16
LMH6734
Physical Dimensions inches (millimeters) unless otherwise noted
16-Pin SSOP
NS Package Number MQA16
17
www.national.com
LMH6734 Single Supply, Ultra High Speed, Triple Selectable Gain Buffer
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