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Sinusoidal Output Phase Lock Loop

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Asher

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Hi all, i'm currently doing a sinusoidal phase lock loop and i don't have any idea how it works, but i have found a schematic that claims to work and produce a sine wave output. I have wired up the circuit, but i'm getting very high frequency noise as my output.

attached is my schematic for the square wave input as well as the pll schematic i have found.

Capture.JPG
Comparator Circuit (Edited).JPG
 
The SIG IN pin of the 74HC4046 is floating and NEVER goes low. Add a 27k resistor to ground.
 
Hi audioguru, I have added a resistor as shown in the diagram, but the output waveform is still not the expected one, as even the dc power supply has been altered. is it a wrong connection?
Output Waveform.JPG
+DC.JPG
-DC.JPG
Capture.JPG
 

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  • photo 1.JPG
    photo 1.JPG
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I think you must remove the negative supply and bias the MAX297 ground pin at half of 5V as shown in its datasheet.
The input to the mAX297 must swing from +1V to +4V maximum.
 
currently this circuit is based on a dual supply configuration (±5V), so is the mid supply voltage level 2.5V or 0V?
Capture.JPG
 
The datasheet for the MAX297 shows a single-polarity +5V supply. The input swings from +1V to +4V and the clock is 0V to +5V. The ground pin is biased at +2.5V.
If you use a dual-polarity supply (why bother?) then the input and clock both must swing negative and positive.
 
Hi audioguru, I've tried doing the 2.5V method, and it seems like i don't get an output waveform. I'm currently troubleshooting to make the signal from the DC Generator smooth and appear as expected, because i suspect the pulse input may be causing the malfunction of the chips
 
You show a comparator with no part number.
You show 4 'scope traces and none have a label saying what they are and none have 0VDC shown. If the first 'scope trace is the SYNC input then it is AWFUL, maybe because the inputs signal level is too high for the comparator input.

What is a DC generator and what is it used for?
 
Ash,
I think you have a problem with the circuit values.
I'm running with my Philips data handbook for the HCT4046A and fig 29 which shows the typical centre frequency as a function of C1. For C1 =820 pF, and R1 = 3 kohm, f0 is about 1 MHz. For R1 = 300 kohm, fo is about 10 KHz. Both these values are given for R2 = open circuit. The HCT4060 looks like it is dividing by 128. I dont like your value of R1 = 100 ohm, I think it should be around 10 K ohm to give f0 equal to say 400 KHz and the divider giving about 3 KHz. When I look at your waveforms and see horizontal values like 20 milli seconds, there is no way 100 ohm looks right.
The HC/HCT range of logic runs at 5 to 12 volt + with respect to ground. The MAX is an output filter and can run with a +/- 5 volt supply.
I gather you are a student and this is an exercise,
Hope this helps.
 
The HC/HCT range of logic runs at 5 to 12 volt + with respect to ground.
NO WAY!
The 74HCxxxx absolute maximum supply is 7V bit they recommend using 3V to 6V. Most work at 2V but not the VCO in the 74HC4046.
 
You show a comparator with no part number.
You show 4 'scope traces and none have a label saying what they are and none have 0VDC shown. If the first 'scope trace is the SYNC input then it is AWFUL, maybe because the inputs signal level is too high for the comparator input.

What is a DC generator and what is it used for?

So sorry about that, the three pictures (in chronological order) are the supposed sine wave output after adding in the 27kΩ resistor, and the output signals from the DC generator when it is connected to the circuit.

The comparator that i'm currently using is LM 741 general purpose op-amp.
The DC generator is used to power my ic chips, set at a constant of +5Vdc and -5Vdc.

What is the input frequency range?
Have you looked frequency at vco and counter outputs?

From the datasheet, it says that the input signal has to be 50% duty cycle for maximum locking range but does not numerically specify the range of frequencies for the input.
VCO centre frequency C1 = 40 pF; R1 = 3 kΩ;VCC= 5 V (HC=19) (HCT=19) MHz

datasheet that i'm referring to:
https://pdf1.alldatasheet.com/datasheet-pdf/view/15612/PHILIPS/74HC4046AN.html

I got the original schematic from the Maxim Integrated website. The link is below:
https://www.maximintegrated.com/app-notes/index.mvp/id/4504
 
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....the three pictures (in chronological order) are the supposed sine wave output after adding in the 27kΩ resistor, and the output signals from the DC generator when it is connected to the circuit.

The DC generator is used to power my ic chips, set at a constant of +5Vdc and -5Vdc.
The output of the comparator is supposed to be a perfect squarewave but it cannot be since your power supply voltages are bouncing all over the place.
Why are the voltages of the POWER SUPPLY (it is not called a DC generator) not steady and are not plus and minus 5V? Your power supply voltages have big pulses instead of being steady.
What is your power supply that makes it so bad? A GENERATOR????
 
You haven't yet told what your circuit should do.
The original circuit was intended to generate sine output at frequencies 20Hz-20khz.
The pll should lock to input pulse frequencies about 2.5kHz-2.5MHz, so your component values R1 and C1 are too small.
741 is way too slow at the higher frequencies.
 
The output of the comparator is supposed to be a perfect squarewave but it cannot be since your power supply voltages are bouncing all over the place.
Why are the voltages of the POWER SUPPLY (it is not called a DC generator) not steady and are not plus and minus 5V? Your power supply voltages have big pulses instead of being steady.
What is your power supply that makes it so bad? A GENERATOR????

My bad. The power supply becomes so pulsated only when it is connected to the circuit, when i connect it directly to the oscilloscope, it shows a nice DC output. I have tried removing individual parts of the circuit, but that does not seem to have an impact on the signal of the power supply.

You haven't yet told what your circuit should do.
The original circuit was intended to generate sine output at frequencies 20Hz-20khz.
The pll should lock to input pulse frequencies about 2.5kHz-2.5MHz, so your component values R1 and C1 are too small.
741 is way too slow at the higher frequencies.

The circuit goes something like this: it converts a 50Hz sine wave input to a 50Hz square wave output that is to be fed into the PLL. After processing the signal, the output of the MAX 297 is supposed to produce a sine wave (assumedly 50Hz) that is locked to the input frequency.

By saying lock to input pulse frequencies of 2.5kHz-2.5MHz, does that refer to the output of my comparator? Because i'm trying to lock onto a 50Hz signal, do i have to change the input frequency?
 
Yes, you should change the input frequency to 64x50=3200Hz and component values so that the pll vco frequency locks to the input frequency or maybe the pll can lock to the harmonics of the 50Hz input, if you set the vco frequency near 3200Hz ?

I had in the previous post the multiplier 128 and it should be 64.
 
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Do you want to use a power supply that works properly? Or if you post the schematic of the one that is defective then maybe we can help you fix it.
 
Hi audioguru, the schematic is as posted earlier, but it seems to be affecting the power supply. I'm currently re-connecting individual circuits one at a time to find out which circuit is causing the disruption in the power supply.

Currently I have isolated the problem to the first circuit. when connected to the 74HC4046 chip, the power supply becomes pulsated instead of a nice dc supply, and the supposed 50%duty cycle pulse output from the LM741 is also distorted as shown in the pictures below:
IMG_5481.JPG

Output of the LM741 Voltage Comparator
IMG_5482.JPG

Power Supply -ve terminal
IMG_5483.JPG

Power Supply +ve terminal
 
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