DPP adds versatility to VFC

  
The basic VFC (voltage-to-frequency converter) in Figure 1 comprises an integrator (IC1) and a Schmitt-trigger circuit (IC2). The integrator converts the dc input voltage, VIN, to a linear voltage ramp, and the Schmitt trigger sets the limits of the integrator`s output voltage. Feedback around both circuits provides the condition for oscillation. The DPP (digitally programmable potentiometer) in Figure 2 adds programmable limits to the Schmitt trigger and adds two powerful features to the VFC.
DPP adds versatility to VFC - schematic

DPP adds versatility to VFC - img1

 the practical range of frequencies is 500 Hz to 25 kHz. Higher bandwidth, rail-to-rail CMOS versions of IC1 and IC2, and a greater R1/R2 ratio can extend the accuracy and range of the circuit. The automated, accurate setting of the scale factor saves manufacturing test time and eliminates the need for expensive, accurate...




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