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TLV9062: tlv9062 TINA stability simulation

Part Number: TLV9062

2821.TLV9062.TSCHi, Team

our customer want to use our TLV9062 as the active filter for their smart speaker, they want to simulate our stability of their SCH. I create the TINA simulation mode of their SCH, pls check the attach file. And now we prefer to simulate the stability of the circuit, such as the phase margin. I using the "AC transfer characteristic" and it shows below result, i am not sure whether it's the phase margin of the circuit, could u help to check and give some comments? Thanks

G.W

 

  • Hello George,

    Thank you for your question.

    The lower waveform is representative of phase angle, however it is possible to separate the feedback path from the amplifier outputs to allow for phase margin to be calculated. By separating the feedback path from the amplifier output, the amplifier output response can be simplified to the  open loop gain multiplied by beta. The AC open loop circuit can be used to simulate the AC characteristics and solve for phase margin.

    The phase margin for your circuit schematic is 73.65 degrees which should operate in a stable condition. Additionally I have attached the modified AC open loop TINA schematic in case you wish to change any component values and check for stability. 

    TI Precision Labs can offer further information on the topic of stability in the link here: https://training.ti.com/ti-precision-labs-op-amps-stability-spice-simulation?context=1139747-1139745-14685-1138805-13850

    Let me know if you have any other questions.

    Regards,

    Jacob

    2821_TLV9062_TINA_Stability_Simulation.TSC

  • Hi, Jacob

    Thanks your comments, and this is really helpful. Base on your suggestion and the online training, we needs to add the larger inductance/cap to simulate the AC open loop circuit.

    This method is helpful to simulate the single feedback path circuit, and since my customer still using our TLV9062 for another circuit, this circuit using 2 feedback path(as you can see the attachment, the R1 and C1), so I didn't know how to using the similar method to calculate the phase margin, could u help to also give some comments?

    Thanks.

    G.W

    7674.2 feedback loop of TLV9062.TSC

  • Hi GW,

    I would do it this way:

    gw_tlv9062.TSC

    And your second circuit:

    gw_tlv9062_1.TSC

    It turns out that your second circuit isn't stable! See also the transient response:

    You should optimize the feedback components in order to improve the phase margin.

    Kai

  • -Jacob

     

    Hey George,

     

    I agree with Kai, the second circuit is unstable.

    Running an AC open loop analysis of the displays a similar result with a phase margin of about 10 degrees.

    To allow for stability analysis I break the loop at the inverting terminal of the amplifier and add a capacitor to simulate the input capacitance for the device (6pF)

     

    TI Precision labs covers the topic of improving stability for multiple feedback systems in the link here: https://training.ti.com/system/files/docs/1336%20-%20Stability%206%20-%20slides.pdf

    With the design recommendations in the TIPL lesson, I increased the feedback capacitor to 50nF, and I changed the value of the feedback resistor from 1k to 10k (at least 100 times the value of the isolation resistor).

    The new phase plot now lacks the sudden changes the previous circuit had, and has a stable phase margin of 77.22 degrees.

    In case you wish to change any other component values I have attached the TINA schematic here: TLV9062_Stability_Analysis_GW.TSC

     

    Let me know if this helps your design goals,

     

    Regards,

     

    Jacob