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LM231, LM331

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SNOSBI2B –JUNE 1999–REVISED MARCH 2013

LM231A/LM231/LM331A/LM331 Precision Voltage-to-Frequency Converters

Check for Samples: LM231, LM331

FEATURES

DESCRIPTION

The LM231/LM331 family of voltage-to-frequency

• Ensured Linearity 0.01% max

converters are ideally suited for use in simple low-

• Improved Performance in Existing Voltage-to-

cost circuits for analog-to-digital conversion, precision

Frequency Conversion Applications

frequency-to-voltage conversion, long-term

• Split or Single Supply Operation

integration, linear frequency modulation or

demodulation, and many other functions. The output

• Operates on Single 5V Supply

when used as a voltage-to-frequency converter is a

• Pulse Output Compatible with All Logic Forms

pulse train at a frequency precisely proportional to the

• Excellent Temperature Stability: ±50 ppm/°C

applied input voltage. Thus, it provides all the

max

inherent advantages of the voltage-to-frequency

conversion techniques, and is easy to apply in all

• Low Power Consumption: 15 mW Typical at 5V

standard voltage-to-frequency converter applications.

• Wide Dynamic Range, 100 dB min at 10 kHz

Further, the LM231A/LM331A attain a new high level

Full Scale Frequency

of accuracy versus temperature which could only be

• Wide Range of Full Scale Frequency: 1 Hz to attained with expensive voltage-to-frequency

modules. Additionally the LM231/331 are ideally

100 kHz

suited for use in digital systems at low power supply

• Low Cost

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 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

CONNECTION DIAGRAM

Figure 1. Plastic Dual-In-Line Package (PDIP)

See Package Number P (R-PDIP-T8)

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2Teflon is a registered trademark of E.

3All other trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (20 pages)

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LM231, LM331 www.ti.com SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 LM231A/LM231/LM331A/LM331 Precision Voltage-to-Frequency Converters Check for Samples: LM231, LM331 FEATURES DESCRIPTION • • The LM231/LM331 family of voltage-to-frequency converters are ideally suited for use in simple lowcost circuits for analog-to-digital conversion, precision frequency-to-voltage conversion, long-term integration, linear frequency modulation or demodulation, and many other functions.
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LM231, LM331 SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 www.ti.com 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. Absolute Maximum Ratings (1) (2) (3) Supply Voltage, VS 40V Output Short Circuit to Ground Continuous Output Short Circuit to VCC Continuous −0.2V to +VS Input Voltage Package Dissipation at 25°C 1.
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LM231, LM331 www.ti.com SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 Electrical Characteristics (continued) All specifications apply in the circuit of Figure 16, with 4.0V ≤ VS ≤ 40V, TA=25°C, unless otherwise specified.
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LM231, LM331 SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 www.ti.com FUNCTIONAL BLOCK DIAGRAM Pin numbers apply to 8-pin packages only.
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LM231, LM331 www.ti.com SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 TYPICAL PERFORMANCE CHARACTERISTICS (All electrical characteristics apply for the circuit of Figure 16, unless otherwise noted.) Nonlinearity Error as Precision V-to-F Converter (Figure 16) Nonlinearity Error Figure 2. Figure 3. Nonlinearity Error vs. Power Supply Voltage Frequency vs. Temperature Figure 4. Figure 5. VREF vs. Temperature Output Frequency vs. VSUPPLY Figure 6. Figure 7.
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LM231, LM331 SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 www.ti.com TYPICAL PERFORMANCE CHARACTERISTICS (continued) (All electrical characteristics apply for the circuit of Figure 16, unless otherwise noted.) 6 100 kHz Nonlinearity Error (Figure 17) Nonlinearity Error (Figure 15) Figure 8. Figure 9. Input Current (Pins 6,7) vs. Temperature Power Drain vs. VSUPPLY Figure 10. Figure 11. Output Saturation Voltage vs. IOUT (Pin 3) Nonlinearity Error, Precision F-to-V Converter (Figure 19) Figure 12.
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LM231, LM331 www.ti.com SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 APPLICATIONS INFORMATION PRINCIPLES OF OPERATION The LM231/331 are monolithic circuits designed for accuracy and versatile operation when applied as voltage-tofrequency (V-to-F) converters or as frequency-to-voltage (F-to-V) converters. A simplified block diagram of the LM231/331 is shown in Figure 14 and consists of a switched current source, input comparator, and 1-shot timer. Figure 14.
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LM231, LM331 SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 www.ti.com However, if the input comparator still detects pin 7 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.
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LM231, LM331 www.ti.com SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 Details of Operation: Precision V-To-F Converter (Figure 16) 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 LM231/331, the timing cycle is initiated. The average current fed into the op-amp's summing point (pin 2) is i × (1.1 RtCt) × f which is perfectly balanced with −VIN/RIN.
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LM231, LM331 SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 www.ti.com In the simple circuit of Figure 18, this current is filtered in the network RL = 100 kΩ and 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.
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LM231, LM331 www.ti.com SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 *Use stable components with low temperature coefficients. Figure 19. Precision Frequency-to-Voltage Converter, 10 kHz Full-Scale with 2-Pole Filter, ±0.01% Non-Linearity Maximum *L14F-1, L14G-1 or L14H-1, photo transistor (General Electric Co.) or similar Figure 20. Light Intensity to Frequency Converter Figure 21.
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LM231, LM331 SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 www.ti.com Figure 22. Long-Term Digital Integrator Using VFC Figure 23. Basic Analog-to-Digital Converter Using Voltage-to-Frequency Converter Figure 24. Analog-to-Digital Converter with Microprocessor Figure 25.
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LM231, LM331 www.ti.com SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 Figure 26. Voltage-to-Frequency Converter with Square-Wave Output Using ÷ 2 Flip-Flop Figure 27. Voltage-to-Frequency Converter with Isolators Figure 28.
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LM231, LM331 SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 www.ti.com Figure 29. Voltage-to-Frequency Converter with Isolators Figure 30.
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LM231, LM331 www.ti.
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LM231, LM331 SNOSBI2B – JUNE 1999 – REVISED MARCH 2013 www.ti.com REVISION HISTORY Changes from Revision A (March 2013) to Revision B • 16 Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 (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.
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