The AD652 synchronous voltage-frequency converter (SVFC) is a powerful component of precision analog-to-digital conversion, providing a typical nonlinearity of 0.002% (Max. 0.005%) at 100 kHz output frequency. The inherent monotonicity of the transfer function and the wide clock frequency range allow conversion time and resolution to be optimized for specific applications.
Functional block diagram
The AD652 is available in five performance levels. JP and KP grades in 20-pin plc packages are specified to operate in the 0°C to +70°C commercial temperature range. The 16-pin cerdip packaged AQ and BQ grades are suitable for industrial temperature ranges from −40°C to +85°C. The AD652SQ operates in the extended temperature range from −55°C to +125°C
The AD652 uses a variation of charge balance technology to perform the conversion function. Instead of relying on the stability of the external capacitance, the AD652 uses an external clock to define the full-scale output frequency. The result is a more stable and linear transfer function with significant application advantages in both single-channel and multi-channel systems. Gain drift uses precise low drift references and low TC, on-chip, thin-film scaling resistance is minimized.
In addition, the initial gain error is reduced to less than 0.5% by fine tuning the laser chip. The analog and digital components of the AD652 are designed to allow single-ended power operation, simplifying the use of isolated power supplies
Product characteristics
1.）Using an external clock to set the full-scale frequency makes the AD652 achieve far better linearity and stability than other monolithic vfc. By using the same clock to drive the AD652 and setting the count period (via a suitable voltage divider), the conversion accuracy remains independent of changes in clock frequency.
2.）The AD652 synchronous VFC requires only one external component (a non-critical integrator capacitor) to operate.
3.）The AD652 includes a buffered, accurate 5 V reference.
4.）The clock input of the AD652 is TTL and CMOS compatible and can also be driven by negative power. Flexible open-collector output stages provide sufficient current sinking capability for TTL and CMOS logic as well as optical couplers and pulse transformers. A capacitance-programmable one-shot is provided for selecting the best output pulse width to reduce power.
5.）The AD652 can also be configured as a synchronous F/V converter for isolating analog signal transmission.
