LMH6722MA National Semiconductor, LMH6722MA Datasheet - Page 10

• Manufacturer Part Number: LMH6722MA
• Description: Operational Amplifier (Op-Amp) IC
• Manufacturer: National Semiconductor

Specifications of LMH6722MA

• No. Of Pins: 14
• Peak Reflow Compatible (260 C): No
• Supply Voltage Max: 12 V
• Leaded Process Compatible: No
• Package / Case: 14-NSOIC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Application Section
to be avoided. See Application Notes OA-7 and OA-26 for
more information on Active Filter applications for Current
Feedback Op Amps.
ENABLE/DISABLE OPERATION USING
(LMH6720 ONLY)
The LMH6720 has a TTL logic compatible disable function.
Apply a logic low (
disabled. Apply a logic high (
the LMH6720 is enabled. Voltage, not current, at the Disable
pin determines the enable/disable state. Care must be exer-
cised to prevent the disable pin voltage from going more
than .8V below the midpoint of the supply voltages (0V with
split supplies, V
cause transistor Q1 to Zener resulting in damage to the
disable circuit. The core amplifier is unaffected by this, but
disable operation could become slower as a result.
Disabled, the LMH6720 inputs and output become high im-
pedances. While disabled the LMH6720 quiescent current is
approximately 500µA. Because of the pull up resistor on the
disable circuit the I
the disabled state. The positive supply current (I
proximately 500µA while the negative supply current (I
only 200µA. The remaining I
through the disable pin.
The disable function can be used to create analog switches
or multiplexers. Implement a single analog switch with one
LMH6720 positioned between an input and output. Create
an analog multiplexer with several LMH6720’s. The
LMH6720 is at it’s best at a gain of 1 for multiplexer appli-
cations because there is no R
DISABLE LIMITATIONS (LMH6720 ONLY)
The feedback Resistor (R
gain configurations. During shutdown the impedance of the
LMH6720 inputs and output become very high (
however R
output impedance.
Do not apply voltages greater than +V
(V
diodes will also conduct if the signal leakage through the
feedback resistors brings the inverting input near either sup-
ply rail.
CC
/2 single supply) to the disable pin. The input ESD
FIGURE 4. Enable/Disable Operation
F
and R
CC
<
/2 with single supplies) doing so could
CC
G
.8V) to the DS pin and the LMH6720 is
are the dominant factor for effective
and I
F
) limits off isolation in inverting
EE
>
G
2.0V), or let the pin float and
currents are not balanced in
EE
to shunt signals to ground.
current of 300µA flows
(Continued)
CC
±
or less than 0V
5V SUPPLIES
CC
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>
) is ap-
1MΩ),
EE
) is
10
LAYOUT CONSIDERATIONS
Whenever questions about layout arise, use the evaluation
board as a guide. The following Evaluation boards are avail-
able with sample parts:
To reduce parasitic capacitances, the ground plane should
be removed near the input and output pins. To reduce series
inductance, trace lengths of components in the feedback
loop should be minimized. For long signal paths controlled
impedance lines should be used, along with impedance
matching 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 anywhere on the board, the smaller ceramic
capacitors should be placed as close to the device as pos-
sible. In addition Figure 2 shows a capacitor (C1) across the
supplies with no connection to ground. This capacitor is
optional, however it is required for best 2nd Harmonic sup-
pression. If this capacitor is omitted C2 and C3 should be
increased to .1µF each.
VIDEO PERFORMANCE
The LMH6714/6720/6722 has been designed to provide ex-
cellent performance with both PAL and NTSC composite
video signals. Performance degrades as the loading is in-
creased, therefore best performance will be obtained with
back terminated loads. The back termination reduces reflec-
tions from the transmission line and effectively masks ca-
pacitance from the amplifier output stage. While all parts
offer excellent video performance the LMH6714 and
LMH6722 are slightly better than the LMH6720.
LMH6714
LMH6720
LMH6722
FIGURE 5. Typical Application with Suggested Supply
SOT
SOIC
SOT
SOIC
SOIC
Bypassing
CLC730216
CLC730227
CLC730216
CLC730227
CLC730231
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