V to Hz 3 Click Board™

Product Code: MIKROE-5250

How Does The V to Hz 3 Click Board™ Work? The V to Hz 3 Click Board™ as its foundation uses the AD7740, a CMOS synchronous Voltage-to-Frequency Converter (VFC), which uses a charge-balanced conversion technique from Analog Devices. The input voltage signal from 0V up to 5V from its VIN terminal is applied to a proprietary front-end based around an analogue modulator that converts the input voltage into an output pulse train. Depending on the analogue input value, the output frequency goes from 10% to 90% of the input frequency provided by the SPI-configurable LTC6903 programmable oscillator, with a maximum input frequency of 1MHz. The analogue input signal to the AD7740 is continuously sampled by a switched capacitor modulator whose sampling rate is set by a master clock (primary input frequency of the AD7740). The input signal may also be buffered, setting the BUF pin of the mikroBUS™ socket to a high logic state before being applied to the sampling capacitor of the modulator, isolating the sampling capacitor charging currents from the analogue input pin.

The AD7740 also contains an on-chip 2.5 V default bandgap reference, the reference input to the core of the AD7740 defining the span of the VFC. Alternatively, an external reference may be used to overdrive the internal reference by applying it to an onboard header marked as REFIN. Alongside SPI communication, this Click board™ also uses several additional pins. The BUF pin mentioned above represents the Buffered mode selection, while the AN pin indicates the presence of an external analogue signal. The last of the enabled pins is the F signal, routed to the INT pin of the mikroBUS™ socket, which can also serve as output frequency from the AD7740 in the same way as the FOUT terminal. The V to Hz 3 Click Board™ can operate with both 3.3V and 5V logic voltage levels selected via the VCC SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to use the communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development. SPECIFICATIONS Type Mixed-signal Applications Can be used for low-cost analogue-to-digital conversion, linear frequency modulation, voltage-to-frequency conversion, and as a variable clock signal generator On-board modules AD7740 - voltage-to-frequency converter from Analog Devices LTC6903 - programmable oscillator from Analog Devices Key Features The synchronous operation, output frequency provided by a programmable oscillator, low power consumption, internal 2.5V reference, 1MHz maximum input frequency, selectable high impedance buffered input and more Interface SPI Compatibility mikroBUS Click board size M (42.9 x 25.4 mm) Input Voltage 3.3V or 5V, External PINOUT DIAGRAM This table shows how the pinout of the V to Hz 3 Click Board™ corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns). Notes Pin Pin Notes Analog Input Indicator AN 1 AN PWM 16 BUF Buffered Mode NC 2 RST INT 15 F AD7740 Frequency SPI Chip Select CS 3 CS RX 14 NC SPI Clock SCK 4 SCK TX 13 NC SPI Data OUT SDO 5 MISO SCL 12 NC SPI Data IN SDI 6 MOSI SDA 11 NC Power Supply 3.3V 7 3.3V 5V 10 5V Power Supply Ground GND 8 GND GND 9 GND Ground ONBOARD SETTINGS AND INDICATORS Label Name Default Description LD1 PWR - Power LED Indicator JP1 VCC SEL Left Logic Level Voltage Selection 3V3/5V: Left position 3V3, Right position 5V