LM331AN/HG

The LM231/LM331 series voltage-to-frequency converters are ideal for simple, low-cost A/D conversion circuits, precision frequency-to-voltage conversion, long-term integration, linear frequency modulation or demodulation, and many other functions. When used as a voltage-to-frequency converter, the output is a pulse train precisely proportional to the applied input voltage. As such, it provides all the inherent advantages of the voltage-to-frequency conversion technique and is easy to use in all standard V/F converter applications. Furthermore, the LM231A/LM331A achieves a new level of high accuracy over temperature that was previously attainable only with expensive V/F modules. This series is particularly suited for use in digital systems operating from low supply voltages, and provides low-cost A/D conversion in microprocessor-controlled systems. The output frequency from a battery-powered V/F converter can easily be transmitted through a simple optical isolator to provide isolation against high common-mode levels. The LM231/LM331 employs a new temperature-compensated bandgap reference circuit that delivers excellent accuracy over the entire operating temperature range at supply voltages as low as 4.0V. Its precision timer circuit features low bias current without sacrificing the fast response required for 100kHz V/F conversion. The output is capable of driving 3 TTL loads, or high-voltage outputs up to 40V, with protection against short circuits to VCC.

Applications

• Data acquisition systems
• Process control
• Analog-to-digital conversion
• Precision frequency-to-voltage conversion
• Long-term integration

Key features

• Maximum linearity guaranteed at 0.01%
• Improved performance over existing voltage-to-frequency converter applications
• Split or single supply operation
• Single 5V supply operation
• Pulse output compatible with all logic families
• Excellent temperature stability: ±50ppm/°C maximum
• Low power consumption: 15mW typical at 5V
• Wide dynamic range: 100dB minimum at 10kHz full-scale frequency
• Wide full-scale frequency range: 1Hz to 100kHz
• Low cost