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TPS65131-Q1: TPS65131TRGERQ1 equations for Output/input ripple, and load transient step response

waqar hyder1
Prodigy 60 points
Part Number: TPS65131-Q1

Hi 

As title suggests, I need to calculate the input and output voltage ripple, and load step response (voltage sag and soar) given the effective input and output capacitance, ESR of capacitors, inductor L , switching frequency,  and input and output voltages.

I have seen the formulas in some TI buck regulator 's datasheets and app notes so was wondering if I can get the same for this dual boost/inverting regulator. 

I am using 3.5V input and +10V/-10V outputs (13mA and 17mA maximum output currents respectively) 

Also for the -10V, the total accuracy (VREF and VNEG) 1% and 2.4% respectively adds to worst case accuracy of 3.4% as given by a TI AE. Is that taken into account the Feedback current error ? is there a accuracy calculator for this regulator that takes into account all variables. Do these VREF/VNEG tolerances stack on top of each other ?

can I get data for accuracy vs Die temperature for these outputs as our -10V load is not that tolerant so we will  try to limit the Die temperature to a narrower range to be able to operate within the load DC limits. can this lower tolerance be guaranteed by design or testing to be statistically applicable to large sample size (99% of parts) ? 

  • 0
    TI__Mastermind 18550 points

    Hello Waqar,

    Thank you for your post but I think we recently addressed these same issues in e-mail communication with you and provided detailed accuracy calculation accounting for worst case tolerances. Unfortunately, we do not have any other data or simulation models to share beyond the information already provided or that which is in the datasheet  for this device. Datasheet indicates that the accuracy specifications are valid over the entire die operating temperature range of -40C to 125C and we can not guarantee lower accuracy based on a narrower temperature range.

    Kind Regards,

    Liaqat

  • 0
    Prodigy 60 points

    HI 

    can you then at least let me know my question about the role of feedback leakage current in your spreadsheet as this is not accounted for there. 

  • 0 in reply to waqar hyder1
    TI__Mastermind 18550 points

    Hello Again,

    Any inaccuracy due to variation in small current into feedback pin is included in the overall feedback regulation voltage specification in the datasheet. That is the reason I did not include a separate item for it in the calculation. So the calculations I provided should give the worst case accuracy errors.

    Kind Regards,

    Liaqat