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Digitally-controlled 555 Astable Multi-vibrator

2015-01-30 09:29  
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Digitally-controlled 555 Astable Multi-vibrator
As shown in the figure 3-9, the vibrator circuit consists of anA/D converter, mirror current source, and a 555 oscillator. The scillation frequency is related to the data input and the controllable reference voltage added. IC1 uses anA/D converter to transform the integrated circuit DAC0800LCN, an eight-digit DAC, and to transform the data to ananlog signal and add it to the b-pole of the mirror current source,so as to control thecollector current,orthe charge current of C in 555 oscillator, to change the frequency of the oscillator.when inlinearity condition, oscillator frequency f=1/1/3(RpefC/D). (VDD/Vref)+0.693R3C