# Frequency multiplying

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#### rahulcet

##### New Member
Hello everyone,
Do you guys know of any IC that can increase the frequency of a square wave input by say 4, I did find an IC to double the frequency. but I really want ine which can increase it by 4 or 8 and I dont want to connect many frequency doubling ckts in series.

##### Banned
What's the reason you can't generate the square wave faster in the first place? It's easier to start with a faster clock and divide it than it is to multiply it. A clock divider is as simple as a single flip flop and daisy chaining them is fine.

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#### rahulcet

##### New Member
The square wave input is not coming from a pIC or something. It is comin from a hall sensor and in no ways is controllable.
Solution?

##### Banned
Since you mention PICs you could use a micro controller to read the incoming frequency and multiply it. Just a little bit of math. You won't be able to get EXACTLY 4 or 8 times the incoming frequency because you're limited by the micro controllers clock but more details about exactly what you're trying to do would be needed to determine if a micro controller would be a good solution.
You may find luck using a PLL to multiply the clock, I can't recommend any IC's unfortunatly but there has to be clock multipliers out there that will multiply from an incoming clock.

#### rahulcet

##### New Member
thanks. but the range of input frequencies would be like 100 to 500 Hz. So I wonder if PICs internal PLL multipying would be helpful. I will definitely think about using PIC to multipply the frequency using program.
thanks nay other help would be very much appreciated

##### Banned
100-500hz? A PIC could do that in it's sleep, for resolution and accuracy I would recommend and AVR because they run at higher clock speeds and have fast I/O then a PIC does, but either would do for 100-500hz. Easily.

#### MikeMl

##### Well-Known Member
How about an old NE565 with a suitable CMOS counter chip to determine the frequency multiplication. For example, a modulo 8 counter would lock the VCO inside the NE565 to the eighth harmonic of the input frequency. The loop filter dynamics could be set up to "average" out timing jitter in the input frequency. That would be harder to do inside a PIC.

#### rahulcet

##### New Member
Thanks all. this should help me.

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