LM331N National Semiconductor, LM331N Datasheet - Page 6

• Manufacturer Part Number: LM331N
• Description: IC, V/F CONVERTER, DIP8, 331
• Manufacturer: National Semiconductor

Specifications of LM331N

• Frequency: 10kHz
• Full Scale Range: 1Hz To 100kHz
• Linearity %: 0.01%
• Supply Voltage Range: 4V To 40V
• Digital Ic Case Style: DIP
• No. Of Pins: 8
• Svhc: No SVHC (15-Dec-2010)
• Operating Temperature Max: 70°C
• Converter Function: VFC
• Full Scale Frequency: 100
• Power Supply Requirement: Single
• Single Supply Voltage (typ): 5/9/12/15/18/24/28V
• Single Supply Voltage (max): 40V
• Single Supply Voltage (min): 4V
• Dual Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Package Type: MDIP
• Bandwidth: 0.1MHz
• Rohs Compliant: Yes
• Converter Type: Voltage/Frequency
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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Typical Performance Characteristics
Power Drain vs V
Typical Applications
PRINCIPLES OF OPERATION OF A SIMPLIFIED
VOLTAGE-TO-FREQUENCY CONVERTER
The LM231/331 are monolithic circuits designed for accu-
racy
voltage-to-frequency
frequency-to-voltage (F-to-V) converters. A simplified block
diagram of the LM231/331 is shown in Figure 3 and consists
of a switched current source, input comparator, and 1-shot
timer.
The operation of these blocks is best understood by going
through the operating cycle of the basic V-to-F converter,
Figure 3 , which consists of the simplified block diagram of
the LM231/331 and the various resistors and capacitors con-
nected to it.
The voltage comparator compares a positive input voltage,
V1, at pin 7 to the voltage, V
comparator will trigger the 1-shot timer. The output of the
timer will turn ON both the frequency output transistor and
the switched current source for a period t = 1.1 R
this period, the current i will flow out of the switched current
source and provide a fixed amount of charge, Q = i x t, into
the capacitor, C
level than V1. At the end of the timing period, the current i will
turn OFF, and the timer will reset itself.
Now there is no current flowing from pin 1, and the capacitor
C
of V1. Then the comparator will trigger the timer and start an-
other cycle.
The current flowing into C
f, and the current flowing out of C
If V
balance. Even a simple V-to-F converter can provide a fre-
quency precisely proportional to its input voltage over a wide
range of frequencies.
L
will be gradually discharged by R
IN
is doubled, the frequency will double to maintain this
and
versatile
L
. This will normally charge V
SUPPLY
(V-to-F)
operation
L
is exactly I
DS005680-34
x
, at pin 6. If V1 is greater, the
L
is exactly V
L
converters
until V
when
AVE
= i x (1.1xR
x
Output Saturation Voltage vs
I
x
falls to the level
OUT
x
up to a higher
/R
applied
L
t
(Pin 3)
C
or
t
. During
V
IN
t
C
/R
t
) x
as
as
L
.
(Continued)
6
DETAIL OF OPERATION, FUNCTIONAL BLOCK
DIAGRAM ( Figure 2 )
The block diagram shows a band gap reference which pro-
vides a stable 1.9 V
over a V
perature coefficient, and typically changes less than
over a 100˚C temperature change.
The current pump circuit forces the voltage at pin 2 to be at
1.9V, and causes a current i = 1.90V/R
i = 135 µA. The precision current reflector provides a current
equal to i to the current switch. The current switch switches
the current to pin 1 or to ground depending on the state of
the R
The timing function consists of an R
comparator connected to the external R
the input comparator detects a voltage at pin 7 higher than
pin 6, it sets the R
switch and the output driver transistor. When the voltage at
pin 5 rises to
flip-flop to reset. The reset transistor is then turned ON and
the current switch is turned OFF.
However, if the input comparator still detects pin 7 higher
than pin 6 when pin 5 crosses
reset, and the current at pin 1 will continue to flow, in its at-
tempt to make the voltage at pin 6 higher than pin 7. This
FIGURE 3. Simplified Block Diagram of Stand-Alone
DS005680-35
S
flip-flop.
S
Voltage-to-Frequency Converter and
range of 3.9V to 40V. It also has a flat, low tem-
2
⁄
3
V
External Components
CC
DC
S
Nonlinearity Error, Precision
F-to-V Converter ( Figure 7 )
, the timer comparator causes the R
output. This 1.9 V
flip-flop which turns ON the current
2
⁄
3
V
CC
, the flip-flop will not be
S
S
flip-flop, and a timer
to flow. For R
DC
t
C
t
is well regulated
network. When
DS005680-36
DS005680-4
s
= 14k,
1
⁄
2
%
S