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TLV3201: Efficient Square-to-Sine Wave Conversion Using TLV3201 and BUF600X1 – Seeking Simplification Options

Anshuman Banik
Prodigy 20 points
Part Number: TLV3201
Other Parts Discussed in Thread: OPA365

Tool/software:

Hello Everyone,

I’ve designed a circuit to convert a square wave to a sinusoidal waveform as part of a signal conditioning module. The architecture involves:

  • A stable multivibrator configuration based on the TLV3201 comparator generates a square wave.

  • A buffer stage using BUF600X1 to prevent loading.

  • Four cascaded low-pass RC filter stages (R = 1.33kΩ, C = 100pF) to attenuate the harmonics and shape the signal into a sine wave.

The simulation results (attached) confirm that the circuit effectively attenuates the higher harmonics and produces a reasonably clean sine wave at the output.

However, I find the use of four RC stages to make the layout unnecessarily bulky and inefficient. I’m seeking recommendations for more elegant or integrated approaches to achieve similar harmonic filtering, preferably with a reduced component count or a more compact design.

Are there any TI devices or application recommendations (e.g., sine wave oscillator ICs, active filtering alternatives) that could simplify this square-to-sine wave conversion task while maintaining waveform integrity?

Looking forward to your insights.

Thanks!

(Schematic)

 (Simulation Results)

  • +1
    TI__Genius 11235 points

    Hi Anshuman,

    What's the reasoning behind cascading 5x RC filters? Is a 5th order low-pass filter necessary for your circuit?

    Higher order filters aren't usually implemented by cascading RC filters. This is because each additional RC stage loads to previous stage, which means the input to output filtering characteristics change as you cascade more and more stages. Another disadvantage of your current circuit is that there is no drive strength at Vout right now (try resistively loading Vout and see what happens to the voltage levels).

    What kind of design requirements do you have for your output sine wave? What's the desired frequency, swing, and attenuation of the harmonics? 

    I've attached a TINA file for you to alter per your own requirements. It includes the same relaxation oscillator implemented with a TLV3201, but with a second order low-pass filter implemented with the OPA365 in the Sallen-Key topology.

    You can use this online tool to help with your filter design: Filter Design Tool

    SineWaveGen.TSC

  • 0 in reply to HO SIU
    Prodigy 20 points

    Hi HO SIU,

    Thanks a lot for your suggestion on the square-to-sine wave conversion. I tried it out, and the design works well—cleaner and more efficient now. I appreciate your help!