LM6310IM NSC [National Semiconductor], LM6310IM Datasheet - Page 11

• Manufacturer Part Number: LM6310IM
• Description: High Speed Low Power Operational Amplifier with TRI-STATE Output
• Manufacturer: NSC [National Semiconductor]

Application Information
GENERAL INFORMATION
The LM6310 is a high speed complementary bipolar amplifi-
er with good video performance The output of the LM6310
can be turned off with a logic level signal on the DISABLE
pin The output then goes to a high impedance state
(TRI-STATE) which makes it easy to multiplex signals with
the LM6310 The LM6310 responds very quickly to the DIS-
ABLE input (under 25 ns) making it useful for video effects
and adding or selecting data from video streams such as
TELTEXT
Note The LM6310 will operate normally when there is no connection to the
The LM6310 has low power consumption for a high speed
part typically
typical current consumption drops below 1 0 mA This
makes the LM6310 ideal for portable video equipment
The LM6310 is available in two package types DIPs for
through hole designs and SO-8 surface mount packages
The LM6310 uses a current feedback design to achieve
good video performance at low current and low cost
Benefits of the LM6310
The LM6310 provides good video performance for consum-
er and portable applications at low current and low cost
The disable option can reduce power consumption in porta-
ble applications
The video multiplexing capability of the disable function can
also be used to improve the testability of systems by provid-
ing an easy means to open the analog signal path and insert
test or reference signals
Since the multiplexing configuration is a function of the out-
put and disable signal wiring using multiple LM6310’s has
some strong advantages over a one chip video multiplexer
First larger multiplexers are possible with careful layout
up to 8 video inputs can be multiplexed
Frequently in multiplexer designs one or more of the input
signals will need to be buffered with an amplifier and the
output may also need a buffer or driver amplifier Wiring up
LM6310s to do multiplexing lets the LM6310 act as both the
input buffer and the output driver This can reduce parts and
save money In addition to reducing cost the signals will go
through fewer amplifiers This can mean improved signal
quality in addition to lower cost
DESIGN ADAPTABILITY AND SYSTEM
DESIGN FLEXIBILITY
Using the LM6310 allows more adaptable cost effective de-
sign If you need a 3 input multiplexer you can make one
avoiding the extra cost of unused devices of quad multiplex-
er If you need a 5 input multiplexer you can design this with
5 LM6310s saving the space and cost of two video multi-
plexer chips
Using the LM6310 on a distributed multiplexer can improve
manufacturing flexibility You can design a low cost system
with the minimal number functions needed for the low end
of the market
TELETEXT digital video information services etc ) can be
designed on to add-in cards Since the LM6310 will operate
normally when the DISABLE input is floating (no con-
DISABLE pin
k
4 0 mA When the output is disabled the
Additional functions (close captioning
11
nection) the additional functions can be built on the add-in
cards By using LM6310s on both the basic board and the
add-in cards video and other signals can be digitally
switched to implement the new add-in functions Using
LM6310s avoids adding the cost of a dedicated multiplexer
in the low cost system and increases design flexibility
EASY TO USE COST-EFFECTIVE CURRENT FEEDBACK
When used with good high speed layout in a circuit like
those shown in the section on typical performance curves
the LM6310 will provide wide bandwidth high slew and
good video performance Modern current feedback devices
can provide higher bandwidth at lower current and at lower
cost than conventional voltage feedback devices
Note on Performance Curves and
Datasheet Limits
Important Performance curves represent an average of parts and are not
COMMON MODE REJECTION RATIO
The CMRR of 50 dB is valid for inputs which are within 1V of
ground for
be within 1V of the center of the V
rails Moving the inputs away from the center of the supplies
will result in reduced performance and non-linearities
NON-INVERTING (
CURRENT vs TEMPERATURE
This curve is relatively flat over temperature (typically under
1
result in only a millivolt shift on the input voltage
OUTPUT VOLTAGE SWING vs LOAD
This curve shows that almost all of the output swing is avail-
able for the 150
75
OUTPUT SIGNAL ISOLATION IN DISABLE MODE
The top graph shows the spectrum analyzer output of an
LM6310 in normal operaiton The 4 MHz peak has an ampli-
tude of 69 mV Note that the reference level is 100 millivolts
(100 mV) second and third harmonics are present and the
noise floor is towards the bottom of the graph
With the LM6310 disabled we need to greatly increase the
gain of the spectrum analyzer to see the feedthrough of the
4 MHz signal Note that the reference level is now 50 micro-
volts (50
the graph The 4 MHz signal now has an amplitude of
28 9 V less than one-thousandth the normal signal
Note that the LM6310 will function normally (output on) with
the DISABLE input (pin 8) left floating (not connected)
PULSE RESPONSE AND GAIN vs FREQUENCY
FOR A
The feedback resistor (R
photo is 1 k
all voltage follower (A
The gain and phase plot for A
usual value of R
gain and phase plots
A) that even an input source impedance of 2 k
video systems
V
e a
limits
V) and the noise floor is towards the middle of
g
5V supplies In other words the input should
1
A value of 1 k
F
e
a
loads usually used in back-terminated
) INPUT
V
348
e a
F
) value for the pulse response
for comparison with the other
1) circuits using the LM6310
V
to 2 k
e a
a
and V
1 was done with the
is recommended for
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b
power supply
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