LMV331M7 National Semiconductor, LMV331M7 Datasheet - Page 9

• Manufacturer Part Number: LMV331M7
• Description: Voltage Comparator IC
• Manufacturer: National Semiconductor

Specifications of LMV331M7

• No. Of Comparators: 1
• No. Of Pins: 5
• Peak Reflow Compatible (260 C): No
• Output Type: TTL/CMOS
• No. Of Circuits: 1
• Leaded Process Compatible: No
• Package / Case: 5-SC70
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Application Circuits
Square Wave Oscillator
Comparators are ideal for oscillator applications. This square
wave generator uses the minimum number of components.
The output frequency is set by the RC time constant of the
capacitor C
The maximum frequency is limited only by the large signal
propagation delay of the comparator in addition to any ca-
pacitive loading at the output, which would degrade the out-
put slew rate.
To analyze the circuit, assume that the output is initially high.
For this to be true, the voltage at the inverting input V
be less than the voltage at the non-inverting input V
to be low, the capacitor C
charge up through the negative feedback resistor R
it has charged up to value equal to the voltage at the positive
input V
V
If:
Then:
When the output switches to ground, the value of V
duced by the hysteresis network to a value given by:
a1
will be given by:
a1
, the comparator output will switch.
1
FIGURE 5. Squarewave Oscillator
and the resistor in the negative feedback R
R
V
V
1
a1
a2
= R
1
= 2V
= V
has to be discharged and will
2
= R
cc
cc
/3
/3
(Continued)
3
DS100080-24
DS100080-8
a
4
c
. For V
. When
a
has to
is re-
4
c
.
9
Capacitor C
ground. The output will return to its high state when the volt-
age across the capacitor has discharged to a value equal to
V
For the circuit shown, the period for one cycle of oscillation
will be twice the time it takes for a single RC circuit to charge
up to one half of its final value. The time to charge the ca-
pacitor can be calculated from
Where V
tor = (2V
and V
One period will be given by:
or calculating the exponential gives:
Resistors R
R
state. The frequency stability of this circuit should strictly be
a function of the external components.
Free Running Multivibrator
A simple yet very stable oscillator that generates a clock for
slower digital systems can be obtained by using a resonator
as the feedback element. It is similar to the free running mul-
tivibrator, except that the positive feedback is obtained
through a quartz crystal. The circuit oscillates when the
transmission through the crystal is at a maximum, so the
crystal in its series-resonant mode.
The value of R
switch symmetrically about +V
and C
the oscillating frequency, insuring a 50% duty cycle by main-
taining a DC voltage at the inverting input equal to the abso-
lute average of the output waveform.
When specifying the crystal, be sure to order series resonant
with the desired temperature coefficient
a2
5
.
to insure that V
C
1
is set to be several times greater than the period of
= Vmax/2 = V
max
FIGURE 6. Crystal controlled Oscillator
cc
/3)
3
1
is the max applied potential across the capaci-
and R
1
must now discharge through R
and R
1/freq = 2(0.694) R
o
4
will go all the way up to V
must be at least two times larger than
2
CC
are equal so that the comparator will
1/freq = 2t
/3
cc
/2. The RC constant of R
4
C
1
cc
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in the high
4
towards
DS100080-7
3