NSC LM231AN, LM231N Datasheet
LM231A/LM231/LM331A/LM331
Precision Voltage-to-Frequency Converters
General Description
The LM231/LM331 family of voltage-to-frequency converters
are ideally suited for use in simple low-cost circuits for
analog-to-digital conversion, precision frequency-to-voltage
conversion, long-term integration, linear frequency modulation or demodulation, and many other functions. The output
when used as a voltage-to-frequency converter is a pulse
train at a frequency precisely proportional to the applied input voltage. Thus, it provides all the inherent advantages of
the voltage-to-frequency conversion techniques, andis easy
to apply in all standard voltage-to-frequency converter applications. Further, the LM231A/LM331A attain a new high
level of accuracy versus temperature which could only be attained with expensive voltage-to-frequency modules. Additionally the LM231/331 are ideally suited for use in digital
systems at low power supply voltages and can provide
low-cost analog-to-digital conversion in
microprocessor-controlled systems. And, the frequency from
a battery powered voltage-to-frequency converter can be
easily channeled through a simple photoisolator to provide
isolation against high common mode levels.
The LM231/LM331 utilize a new temperature-compensated
band-gap reference circuit, to provide excellent accuracy
over the full operating temperature range, at power supplies
as low as 4.0V. The precision timer circuit has low bias currents without degrading the quick response necessary for
100 kHz voltage-to-frequency conversion. And the output
are capable of driving 3 TTL loads, or a high voltage output
up to 40V, yet is short-circuit-proof against V
Features
n Guaranteed linearity 0.01%max
n Improved performance in existing voltage-to-frequency
conversion applications
n Split or single supply operation
n Operates on single 5V supply
n Pulse output compatible with all logic forms
n Excellent temperature stability,
n Low power dissipation, 15 mW typical at 5V
n Wide dynamic range, 100 dB min at 10 kHz full scale
frequency
n Wide range of full scale frequency, 1 Hz to 100 kHz
n Low cost
CC
±
50 ppm/˚C max
LM231A/LM231/LM331A/LM331 Precision Voltage-to-Frequency Converters
June 1999
.
Typical Applications
DS005680-1
*
Use stable components with low temperature coefficients. See Typical Applications section.
**
0.1µF or 1µF, See “Principles of Operation.”
FIGURE 1. Simple Stand-Alone Voltage-to-Frequency Converter
Teflon®is a registered trademark of DuPont
© 1999 National Semiconductor Corporation DS005680 www.national.com
±
with
0.03%Typical Linearity (f=10 Hz to 11 kHz)
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
LM231A/LM231 LM331A/LM331
Supply Voltage 40V 40V
Output Short Circuit to Ground Continuous Continuous
Output Short Circuit to V
CC
Input Voltage −0.2V to +V
Continuous Continuous
T
MINTMAX
S
−0.2V to +V
T
MIN
S
T
MAX
Operating Ambient Temperature Range −25˚C to +85˚C 0˚C to +70˚C
θ
D
D
jA
at 25˚C)
jA
)
1.25W 1.25W
100˚C/W 100˚C/W
Power Dissipation (P
and Thermal Resistance (θ
(N Package) P
Lead Temperature (Soldering, 10 sec.)
Dual-In-Line Package (Plastic) 260˚C 260˚C
ESD Susceptibility (Note 4)
N Package 500V 500V
Electrical Characteristics
=
T
25˚C unless otherwise specified (Note 2)
A
Parameter Conditions Min Typ Max Units
VFC Non-Linearity (Note 3) 4.5V ≤ V
T
≤ TA≤ T
MIN
VFC Non-Linearity V
In Circuit of
Figure 1
Conversion Accuracy Scale Factor (Gain) V
=
15V, f=10 Hz to 11 kHz
S
=
IN
≤ 20V
S
−10V, R
MAX
=
14 kΩ
S
±
±
±
0.003
0.006
0.024
LM231, LM231A 0.95 1.00 1.05 kHz/V
LM331, LM331A 0.90 1.00 1.10 kHz/V
Temperature Stability of Gain T
LM231/LM331
LM231A/LM331A
Change of Gain with V
S
Rated Full-Scale Frequency V
Gain Stability vs Time T
MIN
≤ TA≤ T
, 4.5V ≤ VS≤ 20V
MAX
±
30
±
20
4.5V ≤ VS≤ 10V 0.01 0.1
10V ≤ V
≤ 40V 0.006 0.06
S
=
−10V 10.0 kHz
IN
MIN
≤ TA≤ T
MAX
±
0.02
(1000 Hrs) Scale
Overrange (Beyond Full-Scale) Frequency V
=
−11V 10
IN
INPUT COMPARATOR
Offset Voltage
LM231/LM331 T
LM231A/LM331A T
MIN
MIN
≤ TA≤ T
≤ TA≤ T
MAX
MAX
±
3
±
4
±
3
Bias Current −80 −300 nA
Offset Current
Common-Mode Range T
MIN
≤ TA≤ T
MAX
−0.2 VCC−2.0 V
±
8
TIMER
Timer Threshold Voltage, Pin 5 0.63 0.667 0.70 x V
Input Bias Current, Pin 5 V
All Devices 0V ≤ V
LM231/LM331 V
LM231A/LM331A V
=
15V
S
PIN 5
PIN 5
≤ 9.9V
PIN 5
=
10V 200 1000 nA
=
10V 200 500 nA
±
10
±
0.01
%
Scale
±
0.02
%
Scale
±
0.14
%
Scale
±
150 ppm/˚C
±
50 ppm/˚C
%
±
10 mV
±
14 mV
±
10 mV
±
100 nA
±
100 nA
%
%
Full-
Full-
Full-
/V
/V
Full-
%
S
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Electrical Characteristics (Continued)
=
T
25˚C unless otherwise specified (Note 2)
A
Parameter Conditions Min Typ Max Units
TIMER
V
Output Current R
Change with Voltage 0V ≤ V
Current Source OFF Leakage
Operating Range of Current (Typical) (10 to 500) µA
Stability vs Temperature
Stability vs Time, 1000 Hours
(Reset) I=5 mA 0.22 0.5 V
SAT PIN 5
CURRENT SOURCE (Pin 1)
=
14 kΩ,V
S
PIN 1
=
0
LM231, LM231A 126 135 144 µA
LM331, LM331A 116 136 156 µA
≤ 10V 0.2 1.0 µA
PIN 1
LM231, LM231A, LM331, LM331A 0.02 10.0 nA
All Devices T
=
T
A
MAX
2.0 50.0 nA
REFERENCE VOLTAGE (Pin 2)
LM231, LM231A 1.76 1.89 2.02 V
LM331, LM331A 1.70 1.89 2.08 V
±
60 ppm/˚C
±
0.1
LOGIC OUTPUT (Pin 3)
V
SAT
OFF Leakage
I=5 mA 0.15 0.50 V
I=3.2 mA (2 TTL Loads), T
MIN≤TA≤TMAX
0.10 0.40 V
±
0.05 1.0 µA
SUPPLY CURRENT
LM231, LM231A V
LM331, LM331A V
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating
the device beyond its specified operating conditions.
Note 2: All specifications apply in the circuit of
Note 3: Nonlinearity is defined as the deviation of f
the frequency range 1 Hz to 11 kHz. For the timing capacitor, C
Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor.
=
5V 2.0 3.0 4.0 mA
S
=
40V 2.5 4.0 6.0 mA
S
=
V
5V 1.5 3.0 6.0 mA
S
=
V
40V 2.0 4.0 8.0 mA
S
Figure 4
, with 4.0V≤VS≤40V, unless otherwise noted.
from VINx (10 kHz/−10 VDC) when the circuit has been trimmed for zero error at 10 Hz and at 10 kHz, over
OUT
, use NPO ceramic, Teflon®, or polystyrene.
T
DC
DC
%
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Functional Block Diagram
Pin numbers apply to 8-pin packages only.
DS005680-2
FIGURE 2.
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Typical Performance Characteristics
(All electrical characteristics apply for the circuit of
Figure 4
, unless otherwise noted.)
Nonlinearity Error
as Precision V-to-F
Converter (
Figure 4
)
Frequency vs Temperature
DS005680-25
DS005680-28
Nonlinearity Error
V
vs Temperature
REF
DS005680-26
DS005680-29
Nonlinearity Error vs Power
Supply Voltage
Output Frequency vs
V
SUPPLY
DS005680-27
DS005680-30
100 kHz Nonlinearity Error
(
Figure 5
)
DS005680-31
Nonlinearity Error
(
Figure 1
)
DS005680-32
Input Current (Pins 6,7) vs
Temperature
DS005680-33
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