LM231N/NOPB - NATIONAL SEMICONDUCTOR

Product

Folder

Sample &

Buy

Technical

Documents

Tools &

Software

Support &

Community

LM231

LM331

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

LMx31x Precision Voltage-to-Frequency Converters

1 Features 3 Description

The LMx31 family of voltage-to-frequency converters

1• Ensured Linearity 0.01% Maximum are ideally suited for use in simple low-cost circuits

• Improved Performance in Existing Voltage-to- for analog-to-digital conversion, precision frequency-

Frequency Conversion Applications to-voltage conversion, long-term integration, linear

• Split or Single-Supply Operation frequency modulation or demodulation, and many

other functions. The output when used as a voltage-

• Operates on Single 5-V Supply to-frequency converter is a pulse train at a frequency

• Pulse Output Compatible With All Logic Forms precisely proportional to the applied input voltage.

• Excellent Temperature Stability: ±50 ppm/°C Thus, it provides all the inherent advantages of the

Maximum voltage-to-frequency conversion techniques, and is

easy to apply in all standard voltage-to-frequency

• Low Power Consumption: 15 mW Typical at 5 V converter applications.

• Wide Dynamic Range, 100 dB Minimum at 10-kHz

Full Scale Frequency Device Information(1)

• Wide Range of Full Scale Frequency: PART NUMBER PACKAGE BODY SIZE (NOM)

1 Hz to 100 kHz LM231 PDIP (8) 9.81 mm × 6.35 mm

• Low-Cost LM331

(1) For all available packages, see the orderable addendum at

2 Applications the end of the data sheet.

• Voltage to Frequency Conversions

• Frequency to Voltage Conversions

• Remote-Sensor Monitoring

• Tachometers

Schematic Diagram

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.

LM231

LM331

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

www.ti.com

Table of Contents

8.3 Feature Description................................................. 10

1 Features.................................................................. 18.4 Device Functional Modes........................................ 10

2 Applications ........................................................... 19 Application and Implementation ........................ 11

3 Description............................................................. 19.1 Application Information............................................ 11

4 Revision History..................................................... 29.2 Typical Applications ................................................ 12

5 Description continued........................................... 39.3 System Examples .................................................. 15

6 Pin Configuration and Functions......................... 410 Power Supply Recommendations ..................... 18

7 Specifications......................................................... 411 Layout................................................................... 18

7.1 Absolute Maximum Ratings ...................................... 411.1 Layout Guidelines ................................................. 18

7.2 ESD Ratings.............................................................. 411.2 Layout Example .................................................... 18

7.3 Recommended Operating Conditions....................... 512 Device and Documentation Support................. 19

7.4 Thermal Information.................................................. 512.1 Related Links ........................................................ 19

7.5 Electrical Characteristics........................................... 512.2 Community Resources.......................................... 19

7.6 Dissipation Ratings ................................................... 612.3 Trademarks........................................................... 19

7.7 Typical Characteristics.............................................. 712.4 Electrostatic Discharge Caution............................ 19

8 Detailed Description.............................................. 912.5 Glossary................................................................ 19

8.1 Overview................................................................... 913 Mechanical, Packaging, and Orderable

8.2 Functional Block Diagram......................................... 9Information........................................................... 19

4 Revision History

NOTE: Page numbers for previous revisions may differ from page numbers in the current version.

Changes from Revision B (March 2013) to Revision C Page

• Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional

Modes,Application and Implementation section, Power Supply Recommendations section, Layout section, Device

and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1

Changes from Revision A (March 2013) to Revision B Page

• Changed layout of National Data Sheet to TI format ............................................................................................................. 1

Product Folder Links: LM231 LM331

LM231

LM331

www.ti.com

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

5 Description continued

Further, the LMx31A attain a new high level of accuracy versus temperature which could only be attained with

expensive voltage-to-frequency modules. Additionally the LMx31 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 photo isolator to provide isolation against high common-mode levels.

The LMx31 uses 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 V. 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 40 V, yet is short-circuit-proof against

VCC.

Product Folder Links: LM231 LM331

LM231

LM331

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

www.ti.com

6 Pin Configuration and Functions

P Package

8-Pin PDIP

Top View

Pin Functions

PIN I/O DESCRIPTION

NAME NO.

IOUT 1 O Current Output

IREF 2 I Reference Current

FOUT 3 O Frequency Output. This output is an open-collector output and requires a pullup resistor.

GND 4 G Ground

RC 5 I R-C filter input

THRESH 6 I Threshold input

COMPIN 7 I Comparator Input

VS 8 P Supply Voltage

7 Specifications

7.1 Absolute Maximum Ratings(1)(2)(3)

MIN MAX UNIT

Supply Voltage, VS40 V

Output Short Circuit to Ground Continuous

Output Short Circuit to VCC Continuous

Input Voltage −0.2 +VSV

Lead Temperature (Soldering, 10 sec.) PDIP 260 °C

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings

only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended

Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) All voltages are measured with respect to GND = 0 V, unless otherwise noted.

(3) If Military/Aerospace specified devices are required, please contact the TI Sales Office/Distributors for availability and specifications.

7.2 ESD Ratings VALUE UNIT

V(ESD) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001(1)(2) ±500 V

(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.

(2) Human body model, 100 pF discharged through a 1.5-kΩresistor.

Product Folder Links: LM231 LM331

LM231

LM331

www.ti.com

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

7.3 Recommended Operating Conditions MIN MAX UNIT

LM231, LM231A −25 85 °C

Operating Ambient

Temperature LM331, LM331A 0 70 °C

Supply Voltage, VS(1) 4 40 V

(1) All voltages are measured with respect to GND = 0 V, unless otherwise noted.

7.4 Thermal Information LM312, LM331

THERMAL METRIC(1) P (PDIP) UNIT

8 PINS

RθJA Junction-to-ambient thermal resistance 100 °C/W

(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application

report, SPRA953.

7.5 Electrical Characteristics

All specifications apply in the circuit of Figure 16, with 4.0 V ≤VS≤40 V, TA= 25°C, unless otherwise specified.

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

% Full-

4.5 V ≤VS≤20 V ±0.003 ±0.01 Scale

VFC Non-Linearity (1) % Full-

TMIN ≤TA≤TMAX ±0.006 ±0.02 Scale

%Full-

VFC Non-Linearity in Circuit of Figure 14 VS= 15 V, f = 10 Hz to 11 kHz ±0.024 ±0.14 Scale

LM231, LM231A VIN =−10 V, RS= 14 kΩ0.95 1 1.05 kHz/V

Conversion Accuracy

Scale Factor (Gain) LM331, LM331A 0.9 1 1.1 kHz/V

TMIN ≤TA≤TMAX

LMx31 ±30 ±150 ppm/°C

Temperature Stability 4.5 V ≤VS≤20 V

of Gain LMx31A ±20 ±50 ppm/°C

4.5 V ≤VS≤10 V 0.01 0.1 %/V

Change of Gain with VS10 V ≤VS≤40 V 0.006 0.06 %/V

Rated Full-Scale Frequency VIN =−10 V 10.0 kHz

% Full-

Gain Stability vs. Time (1000 Hours) TMIN ≤TA≤TMAX ±0.02 Scale

Over Range (Beyond Full-Scale) Frequency VIN =−11 V 10%

INPUT COMPARATOR

Offset Voltage ±3 ±10 mV

LM231/LM331 TMIN ≤TA≤TMAX ±4 ±14 mV

LM231A/LM331A TMIN ≤TA≤TMAX ±3 ±10 mV

Bias Current −80 −300 nA

Offset Current ±8 ±100 nA

Common-Mode Range TMIN ≤TA≤TMAX −0.2 VCC −2 V

TIMER

Timer Threshold Voltage, Pin 5 0.63 × VS0.667 × VS0.7 × VS

Input Bias Current, Pin 5 VS= 15 V

All Devices 0V ≤VPIN 5 ≤9.9 V ±10 ±100 nA

LM231/LM331 VPIN 5 = 10 V 200 1000 nA

LM231A/LM331A VPIN 5 = 10 V 200 500 nA

VSAT PIN 5 (Reset) I = 5 mA 0.22 0.5 V

(1) Non-linearity is defined as the deviation of fOUT from VIN × (10 kHz/−10 VDC) when the circuit has been trimmed for zero error at 10 Hz

and at 10 kHz, over the frequency range 1 Hz to 11 kHz. For the timing capacitor, CT, use NPO ceramic, Teflon®, or polystyrene.

Product Folder Links: LM231 LM331

LM231

LM331

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

www.ti.com

Electrical Characteristics (continued)

All specifications apply in the circuit of Figure 16, with 4.0 V ≤VS≤40 V, TA= 25°C, unless otherwise specified.

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

CURRENT SOURCE (PIN 1)

LM231, LM231A RS= 14 kΩ, VPIN 1 = 0 126 135 144 μA

Output Current LM331, LM331A 116 136 156 μA

Change with Voltage 0V ≤VPIN 1 ≤10 V 0.2 1 μA

LM231, LM231A, 0.02 10 nA

Current Source OFF LM331, LM331A

Leakage All Devices TA= TMAX 2 50 nA

Operating Range of Current (Typical) (10 to 500) μA

REFERENCE VOLTAGE (PIN 2)

LM231, LM231A 1.76 1.89 2.02 VDC

LM331, LM331A 1.7 1.89 2.08 VDC

Stability vs. Temperature ±60 ppm/°C

Stability vs. Time, 1000 Hours ±0.1%

LOGIC OUTPUT (PIN 3)

I = 5 mA 0.15 0.5 V

VSAT I = 3.2 mA (2 TTL Loads), 0.1 0.4 V

TMIN ≤TA≤TMAX

OFF Leakage ±0.05 1 μA

SUPPLY CURRENT

VS= 5 V 2 3 4 mA

LM231, LM231A VS= 40 V 2.5 4 6 mA

VS= 5 V 1.5 3 6 mA

LM331, LM331A VS= 40 V 2 4 8 mA

7.6 Dissipation Ratings VALUE UNIT

Package Dissipation at 25°C(1) 1.25 W

(1) The absolute maximum junction temperature (TJmax) for this device is 150°C. The maximum allowable power dissipation is dictated by

TJmax, the junction-to-ambient thermal resistance (θJA), and the ambient temperature TA, and can be calculated using the formula

PDmax = (TJmax - TA) / θJA. The values for maximum power dissipation will be reached only when the device is operated in a severe

fault condition (e.g., when input or output pins are driven beyond the power supply voltages, or the power supply polarity is reversed).

Obviously, such conditions should always be avoided.

Product Folder Links: LM231 LM331

LM231

LM331

www.ti.com

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

7.7 Typical Characteristics

(All electrical characteristics apply for the circuit of Figure 16, unless otherwise noted.)

Figure 1. Non-Linearity Error as Precision V-to-F Converter Figure 2. Non-Linearity Error

(Figure 16)

Figure 4. Frequency vs. Temperature

Figure 3. Non-Linearity Error vs. Power Supply Voltage

Figure 6. Output Frequency vs. VSUPPLY

Figure 5. VREF vs. Temperature

Product Folder Links: LM231 LM331

LM231

LM331

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

www.ti.com

Typical Characteristics (continued)

(All electrical characteristics apply for the circuit of Figure 16, unless otherwise noted.)

Figure 8. Non-Linearity Error (Figure 14)

Figure 7. 100 kHz Non-Linearity Error (Figure 17)

Figure 9. Input Current (Pins 6,7) vs. Temperature Figure 10. Power Drain vs. VSUPPLY

Figure 12. Non-Linearity Error, Precision F-to-V Converter

Figure 11. Output Saturation Voltage vs. IOUT (Pin 3) (Figure 19)

Product Folder Links: LM231 LM331

LM231

LM331

www.ti.com

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

8 Detailed Description

8.1 Overview

8.1.1 Detail of Operation, Functional Block Diagram

The Functional Block Diagram shows a band gap reference which provides a stable 1.9-VDC output. This 1.9 VDC

is well regulated over a VSrange of 3.9 V to 40 V. It also has a flat, low temperature coefficient, and typically

changes less than ½% over a 100°C temperature change.

The current pump circuit forces the voltage at pin 2 to be at 1.9 V, and causes a current i = 1.90 V/RSto flow.

For RS=14 k, 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 upon the state of the R-S flip-flop.

The timing function consists of an R-S flip-flop and a timer comparator connected to the external RtCtnetwork.

When the input comparator detects a voltage at pin 7 higher than pin 6, it sets the R-S flip-flop which turns ON

the current switch and the output driver transistor. When the voltage at pin 5 rises to ⅔VCC, the timer comparator

causes the R-S 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 the voltage on pin 7 as higher than pin 6 when pin 5 crosses ⅔

VCC, the flip-flop will not be reset, and the current at pin 1 will continue to flow, trying to make the voltage at pin 6

higher than pin 7. This condition will usually apply under start-up conditions or in the case of an overload voltage

at signal input. During this sort of overload the output frequency will be 0. As soon as the signal is restored to the

working range, the output frequency will be resumed.

8.2 Functional Block Diagram

Product Folder Links: LM231 LM331

LM231

LM331

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

www.ti.com

8.3 Feature Description

The LMx31 operate over a wide voltage range of 4 V to 40 V.

The voltage at pin 2 is regulated at 1.90 VDC for all values of i between 10 μA to 500 μA. It can be used as a

voltage reference for other components, but take care to ensure that current is not taken from it which could

reduce the accuracy of the converter.

8.4 Device Functional Modes

The output driver transistor acts to saturate pin 3 with an ON resistance of about 50 Ω. In case of overvoltage,

the output current is actively limited to less than 50 mA.

If the voltage on pin 7 is higher than pin 6 when pin 5 crosses ⅔VCC, the LMx31 internal flip-flop will not be

reset, and the current at pin 1 will continue to flow, trying to make the voltage at pin 6 higher than pin 7. This

condition will usually apply under start-up conditions or in the case of an overload voltage at signal input. During

this sort of overload the output frequency will be 0. As soon as the signal is restored to the working range, the

output frequency will be resumed.

Product Folder Links: LM231 LM331

LM231

LM331

www.ti.com

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

9.1 Application Information

9.1.1 Simplified Voltage-to-Frequency Converter

The operation of these blocks is best understood by going through the operating cycle of the basic V-to-F

converter, Figure 13, which consists of the simplified block diagram of the LMx31 and the various resistors and

capacitors connected to it.

The voltage comparator compares a positive input voltage, V1, at pin 7 to the voltage, Vx, at pin 6. If V1 is

greater, the 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 RtCt. During this period, the current i will

flow out of the switched current source and provide a fixed amount of charge, Q = i × t, into the capacitor, CL.

This will normally charge Vxup to a higher 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 CLwill be gradually discharged by RLuntil Vxfalls

to the level of V1. Then the comparator will trigger the timer and start another cycle.

The current flowing into CLis exactly IAVE = i × (1.1×RtCt) × f, and the current flowing out of CLis exactly Vx/RL≃

VIN/RL. If VIN is doubled, the frequency will double to maintain this balance. Even a simple V-to-F converter can

provide a frequency precisely proportional to its input voltage over a wide range of frequencies.

9.1.2 Principles of Operation

The LMx31 are monolithic circuits designed for accuracy and versatile operation when applied as voltage-to-

frequency (V-to-F) converters or as frequency-to-voltage (F-to-V) converters. A simplified block diagram of the

LMx31 is shown in Figure 13 and consists of a switched current source, input comparator, and 1-shot timer.

Figure 13. Simplified Block Diagram of Stand-Alone

Voltage-to-Frequency Converter and

External Components

Product Folder Links: LM231 LM331

LM231

LM331

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

www.ti.com

9.2 Typical Applications

9.2.1 Basic Voltage-to-Frequency Converter

The simple stand-alone V-to-F converter shown in Figure 14 includes all the basic circuitry of Figure 13 plus a

few components for improved performance.

*Use stable components with low temperature coefficients. See Application Information.

**0.1 μF or 1 μF, See Typical Applications.

Figure 14. Simple Stand-Alone V-to-F Converter

with ±0.03% Typical Linearity (f = 10 Hz to 11 kHz)

9.2.1.1 Design Requirements

For this example, the system requirements are 0.05% linearity over an output frequency range of 10 Hz to 4 kHz

with an input voltage range of 25 mV to 12.5 V. The available supply voltage is 15.0 V.

9.2.1.2 Detailed Design Procedure

A capacitor CIN is added from pin 7 to ground to act as a filter for VIN, use of a 0.1 μF is appropriate for this

application. A value of 0.01 μF to 0.1 μF will be adequate in most cases; however, in cases where better filtering

is required, a 1-μF capacitor can be used. When the RC time constants are matched at pin 6 and pin 7, a voltage

step at VIN will cause a step change in fOUT. If CIN is much less than CL, a step at VIN may cause fOUT to stop

momentarily.

Next, we cancel the comparator bias current by setting RIN to 100 kΩto match RL. This will help to minimize any

frequency offset.

For best results, all the components should be stable low-temperature-coefficient components, such as metal-film

resistors. The capacitor should have low dielectric absorption; depending on the temperature characteristics

desired, NPO ceramic, polystyrene, Teflon or polypropylene are best suited.

The resistance RSat pin 2 is made up of a 12-kΩfixed resistor plus a 5-kΩ(cermet, preferably) gain adjust

rheostat. The function of this adjustment is to trim out the gain tolerance of the LMx31, and the tolerance of Rt,

RLand Ct.

Product Folder Links: LM231 LM331

LM231

LM331

www.ti.com

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

Typical Applications (continued)

A 47-Ωresistor in series with the 1-μF capacitor (CL) provides hysteresis, which helps the input comparator

provide the excellent linearity.

This results in the transfer function of ƒOUT = (VIN / 2.09 V) × (RS/ RL) × (1 / RtCt).

9.2.1.3 Application Curve

Figure 15. Output Non-Linearity Error vs. Frequency

Product Folder Links: LM231 LM331

LM231

LM331

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

www.ti.com

Typical Applications (continued)

9.2.2 Precision V-To-F Converter

In this circuit, integration is performed by using a conventional operational amplifier and feedback capacitor, CF.

When the integrator's output crosses the nominal threshold level at pin 6 of the LMx31, the timing cycle is

initiated.

The average current fed into the summing point of the op-amp (pin 2) is i × (1.1 RtCt) × f which is perfectly

balanced with −VIN/RIN. In this circuit, the voltage offset of the LMx31 input comparator does not affect the offset

or accuracy of the V-to-F converter as it does in the stand-alone V-to-F converter; nor does the LM231/331 bias

current or offset current. Instead, the offset voltage and offset current of the operational amplifier are the only

limits on how small the signal can be accurately converted. Since op-amps with voltage offset well below 1 mV

and offset currents well below 2 nA are available at low cost, this circuit is recommended for best accuracy for

small signals. This circuit also responds immediately to any change of input signal (which a stand-alone circuit

does not) so that the output frequency will be an accurate representation of VIN, as quickly as the spacing of the

2 output pulses can be measured.

In the precision mode, excellent linearity is obtained because the current source (pin 1) is always at ground

potential and that voltage does not vary with VIN or fOUT. (In the stand-alone V-to-F converter, a major cause of

non-linearity is the output impedance at pin 1 which causes i to change as a function of VIN).

The circuit of Figure 17 operates in the same way as Figure 16, but with the necessary changes for high-speed

operation.

*Use stable components with low temperature coefficients.

**This resistor can be 5 kΩor 10 kΩfor VS= 8 V to 22 V, but must be 10 kΩfor VS= 4.5 V to 8 V.

***Use low offset voltage and low offset current op-amps for A1: recommended type LF411A

Figure 16. Standard Test Circuit and Applications Circuit, Precision Voltage-to-Frequency Converter

Product Folder Links: LM231 LM331

LM231

LM331

www.ti.com

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

9.3 System Examples

9.3.1 F-to-V Converters

In these applications, a pulse input at fIN is differentiated by a C-R network and the negative-going edge at pin 6

causes the input comparator to trigger the timer circuit. Just as with a V-to-F converter, the average current

flowing out of pin 1 is IAVERAGE = i × (1.1 RtCt) × f.

In the simple circuit of Figure 18, this current is filtered in the network RL= 100 kΩand 1 μF. The ripple will be

less than 10-mV peak, but the response will be slow, with a 0.1 second time constant, and settling of 0.7 second

to 0.1% accuracy.

In the precision circuit, an operational amplifier provides a buffered output and also acts as a 2-pole filter. The

ripple will be less than 5-mV peak for all frequencies above 1 kHz, and the response time will be much quicker

than in Figure 18. However, for input frequencies below 200 Hz, this circuit will have worse ripple than Figure 18.

The engineering of the filter time-constants to get adequate response and small enough ripple simply requires a

study of the compromises to be made. Inherently, V-to-F converter response can be fast, but F-to-V response

can not.

10 kHz Full-Scale, ±0.06% Non-Linearity

*Use stable components with low temperature coefficients.

100 kHz Full-Scale, ±0.03% Non-Linearity

*Use stable components with low temperature coefficients.

**This resistor can be 5 kΩor 10 kΩfor VS=8V to 22V, but must be

10 kΩfor VS=4.5V to 8V.

***Use low offset voltage and low offset current op-amps for A1:

recommended types LF411A or LF356.

Figure 17. Precision Voltage-to-Frequency Figure 18. Simple Frequency-to-Voltage Converter

Converter

Product Folder Links: LM231 LM331

LM231

LM331

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

www.ti.com

System Examples (continued)

*L14F-1, L14G-1 or L14H-1, photo transistor (General Electric Co.)

or similar

10 kHz Full-Scale With 2-Pole Filter, ±0.01% Non-Linearity

Maximum

*Use stable components with low temperature coefficients.

Figure 19. Precision Frequency-to-Voltage Figure 20. Light Intensity to Frequency Converter

Converter,

Figure 21. Temperature to Frequency Converter Figure 22. Long-Term Digital Integrator Using VFC

Figure 23. Basic Analog-to-Digital Converter Using Figure 24. Analog-to-Digital Converter With

Microprocessor

Voltage-to-Frequency Converter

Product Folder Links: LM231 LM331

LM231

LM331

www.ti.com

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

System Examples (continued)

Figure 25. Remote Voltage-to-Frequency Converter Figure 26. Voltage-to-Frequency Converter With

With 2-Wire Transmitter and Receiver Square-Wave Output Using ÷ 2 Flip-Flop

Figure 27. Voltage-to-Frequency Converter With Figure 28. Voltage-to-Frequency Converter With

Isolators Isolators

Figure 29. Voltage-to-Frequency Converter With Figure 30. Voltage-to-Frequency Converter With

Isolators Isolators

Product Folder Links: LM231 LM331

COMP-OUT

IREF

FOUT

GND

VINF

RC_TIME

GND

LOAD

VINF

GND

LM231

LM331

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

www.ti.com

10 Power Supply Recommendations

The LMx31 can operate over a wide supply voltage range of 4 V to 40 V. For proper operation, the supply pin

should be bypassing to ground with a low-ESR, 1-µF capacitor. It is acceptable to use X7R capacitors for this.

For systems using higher supply voltages, ensure that the voltage rating for the bypass caps is sufficient.

11 Layout

11.1 Layout Guidelines

Bypass capacitors must be placed as close as possible to the supply pin. As the LM331 is a through-hole device,

it is acceptable to place the bypass capacitor on the bottom layer.

If an input capacitor to ground is used to clean the input signal, the capacitor should be placed close to the

supply pin.

Use of a ground plane is recommended to provide a low-impedance ground across the circuit.

11.2 Layout Example

Figure 31. Layout Example

Product Folder Links: LM231 LM331

LM231

LM331

www.ti.com

SNOSBI2C –JUNE 1999–REVISED SEPTEMBER 2015

12 Device and Documentation Support

12.1 Related Links

The table below lists quick access links. Categories include technical documents, support and community

resources, tools and software, and quick access to sample or buy.

Table 1. Related Links

TECHNICAL TOOLS & SUPPORT &

PARTS PRODUCT FOLDER SAMPLE & BUY DOCUMENTS SOFTWARE COMMUNITY

LM231 Click here Click here Click here Click here Click here

LM331 Click here Click here Click here Click here Click here

12.2 Community Resources

The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective

contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of

Use.

TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration

among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help

solve problems with fellow engineers.

Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and

contact information for technical support.

12.3 Trademarks

E2E is a trademark of Texas Instruments.

Teflon is a registered trademark of E.

All other trademarks are the property of their respective owners.

12.4 Electrostatic Discharge Caution

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

12.5 Glossary

SLYZ022 —TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.

13 Mechanical, Packaging, and Orderable Information

The following pages include mechanical, packaging, and orderable information. This information is the most

current data available for the designated devices. This data is subject to change without notice and revision of

this document. For browser-based versions of this data sheet, refer to the left-hand navigation.

Product Folder Links: LM231 LM331

PACKAGE OPTION ADDENDUM

www.ti.com 11-Jan-2021

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead finish/

Ball material

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LM231AN/NOPB ACTIVE PDIP P 8 40 RoHS & Green Call TI | SN Level-1-NA-UNLIM -25 to 85 LM

231AN

LM231N/NOPB ACTIVE PDIP P 8 40 RoHS & Green Call TI | SN Level-1-NA-UNLIM -25 to 85 LM

231N

LM331AN/NOPB ACTIVE PDIP P 8 40 RoHS & Green Call TI | SN Level-1-NA-UNLIM LM

331AN

LM331N/NOPB ACTIVE PDIP P 8 40 RoHS & Green Call TI | SN Level-1-NA-UNLIM 0 to 70 LM

331N

(1) The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance

do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may

reference these types of products as "Pb-Free".

RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.

Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based

flame retardants must also meet the <=1000ppm threshold requirement.

(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation

of the previous line and the two combined represent the entire Device Marking for that device.

(6) Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two

lines if the finish value exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information

provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

PACKAGE OPTION ADDENDUM

www.ti.com 11-Jan-2021

Addendum-Page 2

continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.

TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

IMPORTANT NOTICE AND DISCLAIMER

TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCE

DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”

AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY

IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD

PARTY INTELLECTUAL PROPERTY RIGHTS.

These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate

TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicable

standards, and any other safety, security, or other requirements. These resources are subject to change without notice. TI grants you

permission to use these resources only for development of an application that uses the TI products described in the resource. Other

reproduction and display of these resources is prohibited. No license is granted to any other TI intellectual property right or to any third party

intellectual property right. TI disclaims responsibility for, and you will fully indemnify TI and its representatives against, any claims, damages,

costs, losses, and liabilities arising out of your use of these resources.

TI’s products are provided subject to TI’s Terms of Sale (https:www.ti.com/legal/termsofsale.html) or other applicable terms available either

on ti.com or provided in conjunction with such TI products. TI’s provision of these resources does not expand or otherwise alter TI’s

applicable warranties or warranty disclaimers for TI products.IMPORTANT NOTICE

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265