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TLV4113 Spice Model

Samuel Jaffe
Mastermind 25590 points
Other Parts Discussed in Thread: TLV4113, TINA-TI

Hi E2E,

My customer is worried about phase margin in our TLV4113.  The datasheet states a phase margin of 8 degrees (which is concerning) but the spice model does not have stability issues.  Do we have another, more accurate spice model for the TLV4113?

Thanks,

-Sam

  • 0
    TI__Mastermind 27715 points

    Hello Samuel,

    Looking at the dynamic performance section of the TLV4113 data sheet, with a capacitive load of 10pF the phase margin is specified at 66 degrees. I've copied the relevant section below. 

    To check this, I imported the provided PSpice model into TINA-TI and ran an open-loop gain and phase simulation. The result was a unity gain bandwidth of 3.3 MHz and a phase margin of 60 degrees, as shown below. While this is not an exact match, the results are believable within typical device tolerances. The TLV411xA model is also much less sophisticated than our more recent offerings and is not as finely-tuned to match the data sheet. 

    The TINA simulation circuit can be found here: Aol Test - TLV4113.TSC

    Phase margin of the TLV4113 will decrease as the capacitive load increases, but this effect can be reduced to a certain degree by adding a null series resistor at the amplifier output. Please see Figure 17 and the section "driving a capacitive load" in the TLV4113 data sheet.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps

  • 0 in reply to Ian Williams
    TI__Mastermind 25590 points
    Ian,

    Thank you for the detailed response. I believe the problem is that the load is too capacitive (0.01-0.02uF). Increasing Rnull would affect accuracy. Is there any other way around this?
  • 0 in reply to Samuel Jaffe
    TI__Mastermind 27715 points
    Hi Sam,

    I understand the issue now. With a heavy capacitive load such as 10 nF, the current model does not accurately represent the true output impedance of the device and phase margin does not degrade as it should.

    My supervisor and resident stability guru Tim Green will be contacting you via e-mail to resolve the issue. He's working on a new small-signal model for the TLV4113 that will more accurately model Aol and Zo and can be used to effectively compensate the customer's circuit.

    Best regards,

    Ian Williams
  • 0 in reply to Ian Williams
    TI__Mastermind 25590 points
    Brilliant! Thank you so much!