Characteristic operating frequency up to 500kHz
good linearity
±0.01% max at 10kHz FS
±0.05% max at 100kHz FS
V/F or F/V Conversion Monotonic Voltage or Current Input Application Integrated A/D Converter Serial Frequency Output Isolated Data Transmission
FM analog signal modulation/demodulation motor speed control tachometer

Pin configuration

illustrate
The VFC32 voltage-to-frequency converter provides an input voltage that is precisely proportional to its output frequency. The digital open collector frequency output is compatible with all common logic families.
Its integrated input characteristics make VFC32 good noise immunity and low nonlinearity.
The full-scale output frequency is determined by external capacitors and resistors and can be over a wide range. The VFC32 can also be configured as a frequency-to-voltage converter.
The VFC32 is available in 14-pin plastic impregnated, SO-14 surface mount, metal to -100 packs. Commercial, Industrial and Military Temperature Range Models

Electrostatic Discharge Sensitivity This integrated circuit may be damaged by electrostatic discharge. Burr-Brown recommends the use of appropriate precautions. Failure to follow proper operation and installation procedures may result in damage.
ESD damage can range from minor performance degradation to complete device failure. Precision integrated circuits can be more susceptible to damage because very small changes in parameters can cause the device to not meet its published specifications.

application information

Capacitor value selection

Gain and bias voltage trimming circuits.

inverter circuit.

V/F converter negative input voltage.

Basic connection diagram for frequency-to-voltage conversion. R1 sets the input voltage range. For a 10V full-scale input, a 40kΩ input resistor is recommended. Other input voltage ranges can be changed by changing the value of R1. R1 should be metal film type for good stability. Manufacturing tolerances can produce approximately ±10% variation in output frequency. The full-scale output frequency can be trimmed by adjusting the value of R1. The full-scale output frequency is determined by C1. The values shown in Figure 1 are for a full-scale output frequency of 10 Hz. Values for other full-scale frequencies can be read. C1 tolerance, any change in temperature drift, aging directly affects the output frequency. Ceramic NPO or silver mica types are a good choice. For full-scale frequencies above 200kHz, use a larger capacitor value, where R1 = 20kΩ. The value of the integrating capacitor C2 does not directly affect the output frequency, but its value must be chosen within a certain range. The chosen value produces an approximately 2.5Vp-p integrator voltage waveform. If the value of C2 is too low, the integrator output voltage can exceed its linear output swing, resulting in an acceptable nonlinear response.
The accuracy or temperature stability of C2 is not critical as its value does not directly affect the output frequency.
However, for best linearity, C2 should have low leakage and low dielectric absorption. Film capacitors like polycarbonate are generally fine. Many ceramic types are adequate, but some low-voltage ceramic capacitor types may reduce nonlinearity. Electrolytic types are not recommended.
Frequency Output Pin The frequency output is an open collector logic output. Pull-up resistors are usually connected to the 5V logic provided to create standard logic level pulses. But it can, connect to any power supply up to +VCC. The output pulse has a constant duration and is active during a shot. Open collector output current transistors return through common. This terminal should be connected to logic ground.

Frequency-to-voltage conversion VFC32 is connected as a frequency-to-voltage converter. Capacitively coupled input networks C3, R6, and R7 allow standard 5V logic levels to trigger comparator inputs. The comparator triggers on the falling edge of the frequency input pulse. The voltage on the threshold comparator is about -0.7V. The frequency input waveform is less than 5V logic level. The R6/R7 voltage divider can be adjusted down to ensure that the comparator is triggered.
The value of C1 is based on the full-scale input frequency. C2 smoothes the waveform of the output voltage. The larger the value of C2, the smaller the ripple output voltage. Smaller values of C2 allow the output voltage to adapt more quickly to changes in the input frequency.
Resistor R1 can be adjusted to achieve the desired output voltage at the full-scale input frequency.

working principle
The VFC32 works on the principle of charge balancing. This signal input current is equal to VIN/R1. This current is integrated by the input op amp and C2, resulting in a downward ramp to the integrator output voltage. A trigger is a trigger when the integrator output ramps up to the comparator's threshold. The 1 mA reference current switches to the integrator input during one trigger, causing the integrator output to ramp up. After one shot, the integrator slopes down again.
The oscillation process forces a long-term balance (or average current) of charges between the input signal current and the reference current. The charge balance equation is:
where:
fO is the output frequency tOS is one shot cycle, equal to tOS=7500 C1 (farads) (4) Choose the recommended values for R1 and C1 to generate a full-scale frequency output with a 25% duty cycle. For full scale frequencies above 200kHz, the recommended value reduces the duty cycle by 50%.