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ATL431: Questions about a margin of stablity boundary and another topic.

Kazuya Nakai59
Guru 20750 points
Part Number: ATL431
Other Parts Discussed in Thread: ATL432, ,

 Hello guys,

 One of my customers considering using ATL431 or ATL432 for their next products.

 They have the following questions. Could you please give me your reply?

 Q1. Fiqure 19 on page 8 of ATL431/432 datasheet (Version SLSCV5D) shows

       stability boundary conditions at all ATL43x in case of VKA=5V and high IKA range.

       Does this boundary have a margin to cover device variation and tempeature variation?

       Or do I need to add some margin (1/10 or x10 etc) on this boundary?

 Q2. ATL431 and ATL432, which is the major device (=high volume) in W/W?

       Is it ATL431? I want to use the major device. 

 Your reply would be much appreciated.

 Best regards,

 Kazuya.   

  • 0
    TI__Intellectual 1735 points

    Hi Kazuya,

    Q1. The boundary itself is marginal in terms of stability, so you want to add some margin to that to account for PVT variations. A good starting point would be to back off the boundary by a factor of 2 for capacitance (if that is what you can change) or increase IKA to bring the distance from the boundary to be about that much. Please use this as a starting point to determine stability of your system when evaluating it at the harshest conditions you expect your device to be in.

    Q2. Both these parts are the same silicon with different pinouts, so they are both large volume. Sorry, but I cannot tell you which one is higher in volume compared to the other one. You may also want to consider looking at the ATL431LI, as it is a newer part and has higher bandwidth compared to the ATL431.

    I hope this helps!

    -Tony

  • 0 in reply to Tony!
    Guru 20750 points

     Hi Tony,

     Thank you very much for your reply.

     Could I ask you an additional question to your answer for Q1 as the follows?

      Add Q. The customer wants to use ATL431 with VKA=5V and 2mA as the minimum IKA.

                    According to Figure 19, CKA boundary for stablity is about 0.4uF in the condition above.

                    In this case, do you recommend to use 0.2uF as CKA?

      Could you please give me your reply?

     Thank you again and best regards,

     Kazuya.

                     

  • 0 in reply to Kazuya Nakai59
    TI__Intellectual 1735 points

    Hi Kazuya,

    In this case 0.2uF is a good starting point, however depending on production volumes and max/min temperatures, this needs to be validated in final design. Unfortunately, I cannot advise you on a capacitor value that is guaranteed to provide stability in this situation, but the 0.2uF should be good enough to get you started.

    -Tony

  • 0 in reply to Tony!
    Guru 20750 points

     Hi Tony,

     Thank you very much for your reply.

     It is very helpful for the customer and me.

     Thank you again and best regards,

     Kazuya.