2001 Fairchild Semiconductor Corporation
www.fairchildsemi.com
Rev. 1.0.0
Features
Guaranteed linearity: 0.01% max.
Low power dissipation: 15mW at 5V
Wide range of full scale frequency: 1Hz to 100KHz
Pulse output compatible with all logic forms
Wide dynamic range: 100dB min at 10KHz full scale
frequency
Description
This voltage to frequency converter provides the output
pulse train at a frequency precisely proportional to the
applied input voltage. The LM331 can operate at power
supplies as low as 4.0V and be changed output frequency
from 1Hz to 100KHz. It is ideally suited for use in simple
low cost circuit for analog-to digital conversion, long term
integration, linear frequency modulation or demodulation,
frequency to voltage conversion, and many other functions.
Internal Block Diagram
LM331
V-F Converter
8-DIP
1
LM331
2
Absolute Maximum Ratings (T
A
= 25
C)
Electrical Characteristics
Parameter
Symbol
Value
Unit
Supply Voltage
V
CC
40
V
Input Voltage
V
I
-0.2 ~ + V
CC
V
Operating Temperature Range
T
OPR
0 ~ +70
C
Power Dissipation
P
D
500
mW
Parameter
Symbol
Conditions
Min. Typ.
Max.
Unit
VFC Non-Linearity
VFCNL
4.5
V
CC
20V
-
0.003
0.01 % Full-Scale
Conversion Accuracy Scale Factor
ACCUR
V
I
= -10V, R
S
= 14K
0.90
1.00
1.10
KHz/V
Chang Of Gain With V
CC
V
CC
G/V
CC
4.5V
V
CC
10V
-
0.01
0.1
%/V
10V
V
CC
40V
-
0.006
0.06
Rated Full - Scale Frequency
f
V
I
= -10V
10.0
-
-
KHz
INPUT COMPARATOR
Offset Voltage
V
IO
0
C
T
A
+70
C
-
3
10
mV
Bias Current
I
BIAS
-
-
-80
-300
nA
Offset Current
I
IO
-
-
8
100
nA
Common-Mode Range
V
CM
0
C
T
A
+70
C
-0.2
-
V
CC
-
2.0
V
TIMER (PIN 5)
Timer Threshold Voltage
V
TH
-
0.63 0.667
0.701
V
CC
Input Bias Current
I
BIAS
V
CC
= 15V,
0V
V
5
9.9V
-
10
100
nA
V
5
= 10V
-
200
1000
nA
Saturation Voltage
V
SAT
I = 5mA
-
0.22
0.5
V
CURRENT SOURCE (PIN 1)
Output Current
I
O
R
S
= 14K
, V
1
= 0V
116
136
156
A
Change with Voltage
I
O
/
V
1
0V
V
1
10V
-
0.2
1.0
A
Current Source Off Leakage
I
LKG
-
-
0.02
10.0
nA
REFERENCE VOLTAGE (PIN 2)
Reference Voltage
V
REF
-
1.70
1.89
2.08
V
DC
Stability vs Temperature
ST
T
-
-
60
-
ppm/
C
Stability vs Time, 1000Hours
ST
T
-
-
0.1
-
%
LOGIC OUTPUT (Pin 3)
Saturation Voltage
V
SAT
I = 5mA
-
0.15
0.50
V
I = 3.2mA
-
0.10
0.40
Off Leakage
I
LKG
-
-
0.05
1.0
A
SUPPLY CURRENT
Supply Current
I
CC
V
CC
= 5V
1.5
3.0
6.0
mA
V
CC
= 40V
2.0
4.0
8.0
LM331
3
Typical Applications
Figure 1. Precision Voltage-to-Frequency Converter, 100KHz Full-Scale
Figure 2. Simple Frequency-to-Voltage Converter, 10KHz Full-Scale
Figure 3. Light Intensity to Frequency Converter
LM331
LM331
LM331
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