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TPS55340: Load transient response

Jonathan Navor
Genius 9475 points

Part Number: TPS55340

Hi Team,

I'm posting this in behalf of the customer. Kinldly check please.

Here it is:

We have used TI part TPS55340RTER  in one of our design as Boost regulator from 5.5 to 28V with 400mA load for TDMA application.

We have encountered  an issue at system level due to the slow load transient response time from regulator (Fsw=350KHz),  and to mitigate that we have increased the switching frequency from 350KHz to 900KHz but we have kept  all the components  same for both switching  frequencies ( loop filter, inductor and output capacitors).

Our initial design's loop filter values are different from TI's excel file and I tried to modify the values in the design file but it requires a password to unlock the design file. 

I have tried to confirm the stability of the regulator but results were to far from the expectation of Fcross-over of 6KHz, hence I am requesting for your advice on this matter.

1. No.of ways to improve the settling time

2. Password the excel file

3.How to confirm the stability of the loop.

Best regards,

Jonathan

  • 0
    TI__Guru* 79815 points

    Hi Jonathan,

    Thank you for posting.  From your waveforms, the circuit looks stable, just having some undershoot or overshoot during the step load response.  Actually, for a 28V output rail, even the 520mV is less than 2% of the regulation voltage. What is customer's spec to meet?  Also, could you tell what is the step load range?  Between 0A and 400mA?  If it is from 0A to 400mA, at no load the circuit will respond slower because of the diode rectification and DCM mode operation.  Sometimes, adding more output capacitor can easily reduce the Vp-p.  

    Regarding the design calculator, it seems not having a password.  Just clicking "unprotect sheet" it will become opened.  However, I would recommend not to unprotected it during the use, in order to avoid mistakenly altering the designated calculations without notice.

    Could you share the schematic such that our engineer can take a review?

    Thanks,

    Youhao