LMV393MMX/NOPB National Semiconductor, LMV393MMX/NOPB Datasheet - Page 9

• Manufacturer Part Number: LMV393MMX/NOPB
• Description: IC COMP TINY DUAL LOW V 8-MSOP
• Manufacturer: National Semiconductor
• Type: General Purposer

Specifications of LMV393MMX/NOPB

• Number Of Elements: 2
• Output Type: CMOS, Open-Collector, TTL
• Voltage - Supply: 2.7 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• Leaded Process Compatible: Yes
• Rohs Compliant: Yes
• Peak Reflow Compatible (260 C): Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LMV393MMX; LMV393MMXTR

SQUAREWAVE 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
maximum frequency is limited only by the large signal prop-
agation delay of the comparator in addition to any capacitive
loading at the output, which would degrade the output slew
rate.
1
FIGURE 5. Squarewave Oscillator
and the resistor in the negative feedback R
FIGURE 4.
10008024
10008008
10008023
4
. The
9
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:
Capacitor C
The output will return to its high state when the voltage 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 capac-
itor can be calculated from
Where V
= (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 trans-
mission 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
a1
5
to insure that V
will be given by:
CC
C
1
a1
= Vmax/2 = V
/3)
is set to be several times greater than the period of
, the comparator output will switch.
max
1
3
is the max applied potential across the capacitor
must now discharge through R
and R
1
and R
1/freq = 2(0.694) R
O
4
will go all the way up to V
CC
must be at least two times larger than
2
V
R
/3
are equal so that the comparator will
V
1/freq = 2t
a1
1
a2
= R
1
= 2V
= V
has to be discharged and will
2
CC
CC
= R
CC
/2. The RC constant of R
/3
/3
3
4
C
1
4
towards ground.
CC
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in the high
a2
a
4
.
. For V
c
. When
a
has to
is re-
3
c