13-Bit A/D Converter with TC9400 VFC
If we don’t need a very fast analog-to-digital conversion (ADC), by combining TC9400 V/F converter with a counter, latch and time base, we can build a13 bit binary A/D converter. A 1 second time base will provide one conversion per second when the V/F converter is set up for 10KHz full scale.
The high input impedance of TC9400 make it possible to insert a 1M resistor in the input. The linearity of the voltage to frequency converter should be sufficient for 13 bit resolution. You can use standard logic as the base of the time base circuit. You can also use a microcontroller to implement the time base circuit, latch function, and even some microcontrollers provide the counter function at one of their pins. [System’s block diagram source: Microchip Application Note]