• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 145 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS54519: Need the transconductance error amplifier specification

Lionel U
Prodigy 60 points
Part Number: TPS54519
Other Parts Discussed in Thread: TPS54540, TPS62867, TPS62870

Hello
To correctly model the TPS54519 with SIMPLIS, I need the transconductance amplifier specification. 

In the datasheet, only gmea is specified but Aol and BW are missing. For instance in the TPS54540, those information are available.

To correctly estimated Ro, Co (and to use it in the small signal model as below) I need those information.

If I read the average PSPICE model, I found Co=10pF and Ro=2.2Meg but gmea seems to be 220μmhos (different from the typical value of 250μmhos).

Thanks for your support

  • 0
    TI__Guru*** 145250 points

    Hi,

    The values in the spice model look reasonable, and I will try to confirm for this older device.

    Did you already check if the newer TPS62867 would fit your application?

    Thanks,

    Chris

  • 0 in reply to Chris Glaser
    Prodigy 60 points

    Hello Chris

    The TPS54519 is a high runner PN in our product so that's why it's a preferred choice. According to Silicon Expert, the EOL planned is > 10 years. Maybe you've got better estimation of its lifetime. ?
    The TPS62867 let us not playing with the compensation in order to play with Fc and PM (we've got a very tight over/undershoot requirement during load transient. Webench is totally blind on AC response for this part. So really not a good choice for us.

    Coming back to TPS54519, yes please if you can confirm me the Aol and BW ?
    Moreover I found that Webench is not correctly simulating the type III compensation. For sentence, if you remove the feedforward capacitor (Cff,) Fc and PM will stay the same !!!

    Thanks for your support
    Best Regards
    Lionel

  • 0 in reply to Lionel U
    TI__Guru*** 145250 points

    Hi Lionel,

    Thanks for explaining.  You can use the 10pF and 2.2Mohm values from the model.

    The TPS62867's DCS-Control (constant on time type) should have better transient response than a current mode system.  But, as you noted, you cannot adjust the compensation.

    If the transient response is critical for your applications, I recommend the TPS62870.  This uses external compensation and has a very fast transient response, like a constant on time.  Let me know if you have more questions on that one.

    Thanks,

    Chris

  • 0 in reply to Chris Glaser
    Prodigy 60 points

    Chris

    We prefer continuing form TPS54519 as we have volume on it, except if you confirm me the EOL is < 10 year.
    Thanks for the param model confirmation.

  • 0 in reply to Lionel U
    TI__Guru*** 145250 points

    Yes, at this time TPS54519 should be active for a while.  The TPS62867 and TPS62870 are newer devices on newer processes, which would be active for longer (maybe 20+ years instead of 10+ years).

    See also TI's lifecycle summary: https://www.ti.com/support-quality/quality-policies-procedures/product-life-cycle.html

    Chris