LMV7275MG National Semiconductor, LMV7275MG Datasheet - Page 10

• Manufacturer Part Number: LMV7275MG
• Description: IC,VOLT COMPARATOR,SINGLE,BICMOS,TSSOP,5PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LMV7275MG

• Rohs Compliant: NO

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Application Notes
BASIC COMPARATOR
A comparator is often used to convert an analog signal to a
digital signal. As shown in Figure 2, the comparator com-
pares an input voltage (V
RAIL-TO-RAIL INPUT STAGE
The LMV727X has an input common mode voltage range
(V
achieved by using paralleled PNP and NPN differential input
pairs. When the V
PNP pair is off. When the V
and the PNP pair is on. The crossover point between the
NPN and PNP input stages is around 950mV from V
each input stage has its own offset voltage (V
the comparator becomes a function of the V
for V
tion. In application design, it is recommended to keep the
V
wide input voltage range makes LMV727X ideal in power
supply monitoring circuits, where the comparators are used
to sense signals close to ground and power supplies.
OUTPUT STAGE
The LMV7271 and LMV7272 have a push-pull output stage.
This output stage keeps the total system power consumption
to the absolute minimum. The only current consumed is the
low supply current and the current going directly into the
load. When the output switches, both PMOS and NMOS at
the output stage are on at the same time for a very short
time. This allows current to flow directly between V
through output transistors. The result is a short spike of
current (shoot-through current) drawn from the supply and
glitches in the supply voltages. The glitches can spread to
other parts of the board as noise. To prevent the glitches in
supply lines, power supply bypass capacitors must be in-
stalled. See section for supply bypassing in the Application
Notes for details.
CM
CM
OS
) of −0.1V below the V
away from the crossover point to avoid problems. The
vs. V
CM
in Typical Performance Characteristics sec-
CM
is near V
IN
LMV7271
) to a reference voltage (V
CM
−
is near V
+
, the NPN pair is on and the
to 0.1V above V
−
, the NPN pair is off
20064025
FIGURE 2. LMV7271 Basic Comparator
CM
OS
. See curves
), the V
+
. This is
+
+
and V
REF
. Since
OS
). If
of
−
10
V
is greater than V
HYSTERESIS
It is a standard procedure to use hysteresis (positive feed-
back) around a comparator, to prevent oscillation, and to
avoid excessive noise on the output because the comparator
is a good amplifier of its own noise.
Inverting Comparator with Hysteresis
The inverting comparator with hysteresis requires a three
resistor network that is referenced to the supply voltage V
of the comparator (Figure 3). When V
is less than V
comparator (V
plicity assume V
network resistors can be represented as R
R
When V
low and very close to ground. In this case the three network
resistors can be presented as R
upper trip voltage V
The total hysteresis provided by the network is defined as
A good typical value of ∆V
50mV. This is easily obtained by choosing R
times (R
(R
IN
2
1
. The lower input trip voltage V
||R
is less than V
2
) for 1.8V operation.
IN
1
||R
is greater than V
2
A
) for 5V operation, or as 300 to 30 times
IN
, the voltage at the non-inverting node of the
REF
<
REF
O
V
A2
switches as high as V
, the output voltage (V
, the output (V
A
∆V
), the output voltage is high (for sim-
is defined as
A
= V
A
A
(V
would be in the range of 5 to
A1
IN
2
>
- V
//R
A1
O
V
A2
3
) is low. However, if V
is defined as
A
IN
), the output voltage is
in series with R
at the inverting input
1
||R
O
3
) is high.
CC
as 1000 to 100
3
). The three
in series with
20064017
1
. The
CC
IN