High Precision Voltage- to-Frequency Converter

A bipolar high precision voltage-to-frequency converter is described. The circuit includes an input voltage-to-current conversion stage followed by a current-controlled multivibrator. The multivibrator trigger includes a window comparator with a limiter of the output voltage swing, and the timing capacitor discharge current is switched simultaneously with the window comparator bias. This allows to obtain high resolution near both trigger thresholds. The circuit simulation shows that the converter provides an accuracy better than 2% in the range 100Hz-100kHz of the output frequency. The breadborded circuit was tested in the temperature range -25OC to 75OC and provided the temperature coefficient: of the output frequency less than 60 PpmlOC. The converter can be fabricated using an ASIC process.