• TI Thinks Resolved

TL712: Detecting Phase difference between a Sine wave and a square wave

Part Number: TL712

Hi,

In one of our designs, there are two signals: 

1) A square wave with 0 to 30V and frequency 500 HZ

2) A sine wave with amplitude 25V, frequency 500HZ.

It is required to find the phase between these two. Please suggest the best way to implement this.

Thanks in advance.

Regards,

Madhu.

  • Hello Madhu,

    There are several methods of phase detection. A simple method would be to subtract the analog signals to get a signal that its amplitude increases with increasing phase difference. But that would require both signals to be analog and equal amplitude and linearity. Not knowing enough about the details of your circuit, I can only comment that you probably need to step down and normalize the signal amplitudes and use a differential comparator for phase detection. Also you may want to convert the sine wave to a square wave using a comparator with very low prop delay, normalize the signal amplitudes and use XOR (exclusive OR) phase detection method.

    A better way would be to use PLL (Phase -Locked loop) ICs such as CD4046. You need to condition the signals to the proper levels and connect them to the PLL IC as shown in the attached documents.

    Thanks for considering TI products!

    PLL_App_scha003b.pdfPhase_detector_note.pdfCD4046B_scha002a.pdf

  • In reply to Bahram Mirshab:

    Hi,

    Thanks a lot for the valuable information.

    As suggested, I am planning to use the PLL. May I know what kind of signal conditioning necessary ?

    Since the signals are from noisy environment, I am planning to use a sine wave to square wave conversion using LM2901 comparator, and an active Low pass filter ( using LMP7701MF/NOPB with necessary amplification).

    Is there anything else that i have to look into before sending to PLL?


    Thanks & Regards,
    Madhu.
  • In reply to Madhu Sharma:

    Hello Madhu,
    You are on the right track, please ensure the signal conditioning stages do not affect the phase characteristic of the signal. The TI Precision Labs online training at the link below will provide you a wealth of information about designing opamp circuits. If not already done so, please check it out

    training.ti.com/ti-precision-labs-op-amps