V to Hz 2 Click is a device that converts an analog voltage input signal into a pulse wave signal of a certain frequency. It has a linear response, so applying a voltage in a range of 0 to 3.3V on its input, will result in generating the pulse train with frequency linearly proportional to the input voltage. This Click features very good linearity, covers a frequency range between 200 Hz to 120 kHz, and it has good temperature stability.
This device is well suited to be used in a number of various voltage to frequency applications: it can be used in instrumentation applications, industrial, and automation markets. It is well suited for use in AD conversion, long-term integration, linear frequency modulation, voltage-to-frequency conversion and it can be used as the variable clock signal generator. Its function can be complemented by the Hz to V 2 Click, which does the opposite type of conversion: frequency into DC voltage. This can be utilized to build an FM modulator/demodulator application, for example.
The main component of the V to Hz 2 Click is the VFC32KU, a voltage-to-frequency and frequency-to-voltage converter from Texas Instruments. It accepts voltage at its input and generates a pulse train, with a frequency linearly proportional to the input voltage. The pulse train is routed to a screw terminal labeled as FOUT, as well as the mikroBUS™ INT pin, labeled as FO. The signal can be then further processed by the host MCU.
When V to Hz 2 Click is operated for the first time, it needs to be calibrated. The Click is equipped with two variable resistors for gain and offset fine-tuning. A calibration procedure should be executed before the first use of the Click board™ since even slight variations in the components tolerances could affect the value at the output. It is recommended to correct the offset after longer time intervals, to compensate for the aging of the passive components on the Click board™. It is done by introducing a known voltage at the input, and adjusting the gain and the offset, until the signal with the expected frequency appears on the output.
As already discussed, V to Hz 2 Click is equipped with the input voltage terminal (VEXT), which is used to connect the control voltage up to 3.3V. Besides having control voltage input on this terminal, it is possible to select the voltage generated by the MCU as the control voltage input, too. INPUT SEL switch can be set so that the PWM pin from the mikroBUS™ is used as the control voltage input. The PWM signal generated by the MCU is filtered out by the onboard low pass filter so that the control voltage remains constant.
The VFC32KU IC requires a dual power supply with ±15V. Therefore, this Click board™ utilizes another IC in order to provide the required voltages. It uses the TPS65131, a positive and negative output DC/DC Converter, from Texas Instruments. This DC/DC converter has already been used in Boost-INV 2 click, so it was tested "on the field" for this purpose. Providing well-stabilized output with the plenty of power headroom, it is a perfect solution for the V to Hz 2 Click, also.
To enable the conversion circuitry, the EN pin of the TPS65131 boost converter should be pulled to a HIGH logic level. This will activate the boost converter and provide the required power for the VFC32KU IC. This pin is routed to the mikroBUS™ CS pin and it is labeled as EN.
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