voltage frequency synthesizer PLL


Posted on Aug 4, 2012

The µA2240 consists of four basic circuit elements: (1) a time-base oscillator, (2) an eight-bit counter, (3) a control flip-flop, and (4) a voltage regulator. The basic frequency of the time-base oscillator (TBO) is set by the external time constant determined by the values of R1 and Cl (1R1C1 = 2 kHz). The open-collector output of the TBO is connected to the regulator output via a 20 k ohm pull-up resistor, and drives the input to the eight-bit counter. At power-up, a positive trigger pulse is detected across C2 which starts the TBO and sets all counter outputs to a low state.


voltage frequency synthesizer PLL
Click here to download the full size of the above Circuit.

Once the µ2240 is initially triggered, any further trigger inputs are ignored until it is reset. In this astable operation, the µ2240 will free-run from the time it is triggered until it receives an external reset signal. Up to 255 discrete frequencies can be synthesized by connecting different counter outputs.




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