Published:2011/7/5 0:07:00 Author:Zoey | Keyword: 555 Linear Voltage, Frequency Converter, Circuit | From:SeekIC
As shown in the picture 5-36, this linear voltage/frequency converter is a practical voltage/frequency converter. When input voltage is strengthened, voltage on C1 will have a linear increase, when it reaches 2/3 VDD, VT1 will conduct and make VT1 discharge promptly. Backhaul time is related to R5C3 time constant. That is,as soon asvoltage on C3 declines to 1/3 VDD, 555 will reset.VT1 will ceases to work, then next timing begins.
Backhaul time of this circuit is only 1μs. The relationship between voltage input and converter frequency can be expressed by following formula:
f=3/2•Vin/VDDR1C1
V/F of parameter in the picture is f ≈10³Vin. If frequency exceeds 10kHz, nonlinear error will be about 0.2%.
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