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TPS51200: Inrush Current on VLDOIN & VO pins

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Replies: 13

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Part Number: TPS51200

Dear, Sir.

My question is related to the contents of this thread;

e2e.ti.com/.../767850

My customer apply TPS51200 for DDR3. SO, they was facing the inrush

input current on VLDOIN & outout on VO pins. They apply TPS51200 for DDR3.

They tried to add 1 ohm resistor between VLDOIN and VREF pin, then

the input peak was reduced from 2.75A to 0.688A.

So, I would like to confirm followings;

1. Is it no problem on this kind of usage for TPS51200?

2. If no problem, How much voltage drop should be estimated on VLDOIN

   pin?

3. Personally, I think Trcking Start-up and shutdown is not so good for

   DDR. Because DDR has the initialization time inside.

   S3 and pseudo S5 is better to escape from unknown VTT setting

   inside of DDR. How do you think about my thinking?

I an hoping to get your advice.

Best Regards,

H. Sakai

  • In reply to hideyuki sakai:

    Hi Sakai, 

    Any update with input inductor idea?

    Thanks

    Qian

  • In reply to Qian Chen:

    Dear, Qian-san. 

    Sorry for my delayed reply. 

    We suppose your inductor idea is to utilize the DCR. 

    Their conclusion is ; 

    4.7uH will be needed with safety margin. DCR is closed to 1ohm. 

    This solution is hard to realize considering the limitation on PCB size & total cost. 

    Best Regards, 

    H. Sakai

  • In reply to hideyuki sakai:

    Hi Sakai, 

    Thanks for the update. 

    As customer is using 4.7uF cap to solve this problem, I will close this post. 

    Thanks

    Qian

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