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TPS745-Q1: TPS745-Q1 have any simulation modeling or data about stability analysis with Bode Plot.

Weng Tzannbor
Prodigy 20 points
Part Number: TPS745-Q1

Tool/software:

TPS745-Q1 have any  simulation modeling or data about stability analysis with Bode Plot.

(1) Gain Margin

(2) Phase Margin

(3) Including temperature effect (-40C, 85C ...)

  • +1
    TI__Mastermind 43585 points

    Hi,

    Do you have any operating conditions of interest? The bandwidth of the device is highly dependent on the load current (bandwidth increases with increasing load), so the Bode stability analysis also has a strong dependence on the load current. Other factors (e.g. if there is a feedforward capacitor, and the amount of output capacitance) also affect it. 

    I have ran some simulations in the past for full load (500mA) if that would be of interest as well. I have the test bench set up so I can run for your conditions if you would rather that. To be clear, I'm using the transistor model for the simulations.

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Prodigy 20 points
    (1) Input Voltage = 3.3V
    (2) Output Voltage = 1.3V @ Ilout = 50mA ~75mA
    (3) Driving condition : Rising & Falling time = 20mA/us
    (4) Cout = 1uF, 4.7uF & Cin =1uF
    (5) Feedback Capacitor value =10nF
    Thanks for your reply ~
  • 0 in reply to Weng Tzannbor
    TI__Mastermind 43585 points

    Hi,

    Before I start the simulation I would like some clarification for some of the setup specifications. 

    (2)  Output Voltage = 1.3V - there is a fixed-output device available with VOUT = 1.3V, but you also mentioned to include a feedforward capacitor, which implies the adjustable device. Just want to confirm whether you are interested in the fixed or adjustable device.

    (3) This condition is a different test than a Bode plot. This sounds more like a load transient response test (although the Bode plot and load transient response for the same condition are closely correlated). Are you asking for load transient plots as well?

    (4) Is COUT = 1uF || 4.7uF, or do you want one test where COUT = 1uF and another where COUT = 4.7uF?

    Thanks,

    Nick

  • +1 in reply to Nick Butts
    Prodigy 20 points

    Dear Nick,

    (2)  Output Voltage = 1.3V - there is a fixed-output device available with VOUT = 1.3V --> Yes,  fixed-output.

    (3)  Are you asking for load transient plots as well ? --> Nice to have. 

          This sounds more like a load transient response test (although the Bode plot and load transient response for the same condition are closely correlated).

          --> Yes, but we want to understand how about gain margin or phase margin @ 10nF (with a Feedback Capacitor ) ?

    (4)  do you want one test where COUT = 1uF and another where COUT = 4.7uF ? --> You are right.

  • 0 in reply to Weng Tzannbor
    TI__Mastermind 43585 points

    Hi,

    Weng Tzannbor said:
    (2)  Output Voltage = 1.3V - there is a fixed-output device available with VOUT = 1.3V --> Yes,  fixed-output.
    Weng Tzannbor said:
      --> Yes, but we want to understand how about gain margin or phase margin @ 10nF (with a Feedback Capacitor ) ?

    Got it, so you are interested in the fixed device. The feedforward capacitor is only possible when using an adjustable device, so are you asking to compare the fixed device with the adjustable device with a feedforward capacitor?

    Weng Tzannbor said:
    (3)  Are you asking for load transient plots as well ? --> Nice to have. 

    Please provide specifications for the load transients - starting and ending current, and the ramp rate for both. 

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Prodigy 20 points

    Got it, so you are interested in the fixed device. The feedforward capacitor is only possible when using an adjustable device, so are you asking to compare the fixed device with the adjustable device with a feedforward capacitor ? --> Yes

    Please provide specifications for the load transients - starting and ending current, and the ramp rate for both. 

    --> 50mA ~ 75 mA  @ 20mA / us (  ramp rate for both )

    Regards,

  • +1 in reply to Weng Tzannbor
    TI__Mastermind 43585 points

    Hi,

    Okay I think it's clear now. Please allow me 3-5 business days to finish the simulations.

    Regards,

    Nick

  • 0 in reply to Weng Tzannbor
    TI__Mastermind 43585 points

    Hi,

    See the attached for the requested simulation data.

    TPS745-Q1_Stability_Analysis.pptx

    Regards,

    Nick