LMC8101MM National Semiconductor, LMC8101MM Datasheet - Page 15

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LMC8101MM

Manufacturer Part Number
LMC8101MM
Description
IC,Operational Amplifier,SINGLE,CMOS,TSSOP,8PIN,PLASTIC
Manufacturer
National Semiconductor
Datasheets

Specifications of LMC8101MM

Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant

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Application Notes
SHUTDOWN FEATURES
The LMC8101 is capable of being turned off in order to
conserve power. Once in shutdown, the device supply cur-
rent is drastically reduced (1µA maximum) and the output will
be "Tri-stated".
The shutdown feature of the LMC8101 is designed for flex-
ibility. The threshold level of the SD input can be referenced
to either V
the SL input is connected to V
referenced to V
1.5V from the supply tied to the SL pin. So, for this example,
the device will be in shutdown as long as the SD pin voltage
is within 1V of V
"chatter" between active and shutdown states, hysteresis is
built into the SD pin transition (see Figure 1 for an illustration
of this feature). The shutdown threshold and hysteresis level
are independent of the supply voltage. Figure 1 illustration
applies equally well to the case when SL is tied to V
horizontal axis is referenced to V
should not be set within the voltage range from 1.1V to 1.9V
of the selected supply voltage since this is a transition region
and the device status will be undetermined.
Table 1, below, summarizes the status of the device when
the SL and SD pins are connected directly to V
In case shutdown operation is not needed, as can be seen in
Table 1, the two pins SL and SD can simply be connected to
opposite supply nodes to achieve "Active" operation. The SL
and SD should always be tied to a node; if left unconnected,
these high impedance inputs will float to an undetermined
state and the device status will be undetermined as well.
With the device in shutdown, once "Active" operation is
initiated, there will be a finite amount of time required before
the device output is settled to its final value. This time is less
than 15µs. In addition, there may be some output spike
during this time while the device is transitioning into a fully
FIGURE 1. Supply Current vs. "SD" Voltage
SL
V
V
V
V
-
TABLE 1. LMC8101 Status Summary
+
+
or V
-
-
+
. In order to ensure that the device would not
and vice versa. This threshold will be about
by setting the level on the SL input. When
SD
V
V
V
V
+
+
-
, the SD threshold level is
LMC8101 Status
+
Shutdown
Shutdown
instead. The SD pin
Active
Active
10124082
-
or V
+
and the
+
:
15
operational state. Some applications may be sensitive to this
output spike and proper precautions should be taken in order
to ensure proper operation at all times.
TINY PACKAGE
The LMC8101 is available in the micro SMD package as well
the 8 pin MSOP package. The micro SMD package requires
approximately 1/4 the board area of a SOT23. This package
is less than 1mm in height allowing it to be placed in absolute
minimum height clearance areas such as cellular handsets,
LCD panels, PCMCIA cards, etc. More information about the
micro
www.national.com/appinfo/microsmd.
CONVERSION BOARDS
In order to ease the evaluation of tiny packages such as the
micro SMD, there is a conversion board (LMC8101CONV)
available to board designers. This board converts a micro
SMD device into an 8 pin DIP package (see Figure 2,
Conversion Board Pin out diagram) for easier handling and
evaluation. This board can be ordered from National Semi-
conductor by contacting http://www.national.com .
INCREASED OUTPUT CURRENT
Compared to the LMC7101, the LMC8101 has an improved
output stage capable of up to three times larger output
sourcing and sinking current. This improvement would allow
a larger output voltage swing range compared to the
LMC7101 when connected to relatively heavy loads. For
lower supply voltages this is an added benefit since it in-
creases the output swing range. For example, the LMC8101
can typically swing 2.5Vpp with 2mA sourcing and sinking
output current (Vs = 2.7V) whereas the LMC7101 output
swing would be limited to 1.9Vpp under the same conditions.
Also, compared to the LMC7101 in the SOT23 package, the
LMC8101 can dissipate more power because both the
MSOP and the micro SMD packages have 40% better heat
dissipation capability.
LOWER 1/f NOISE
The dominant input referred noise term for the LMC8101 is
the input noise voltage. Input noise current for this device is
of no practical significance unless the equivalent resistance
it looks into is 5MΩ or higher.
The LMC8101’s low frequency noise is significantly lower
than that of the LMC7101. For example, at 10Hz, the input
referred spot noise voltage density is 85 nV
pared to about 200nV
quency range of 0.1Hz to 100Hz, the total noise of the
LMC8101 will be approximately 60% less than that of the
LMC7101.
FIGURE 2. micro SMD Conversion Board pin-out
SMD
package
can
for the LMC7101. Over a fre-
be
10124089
found
www.national.com
at:
as com-
http://

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