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TPS51220A: Can we using the Vout2 connect to V5SW when vout2 is 5V?

liang mike
Prodigy 30 points
Part Number: TPS51220A

Hi Ti 

We use TP51220A  for dual dc dc output. Vout1 is 12V and Vout2 is 5V. Can we using the Vout2 connect to V5SW? The switch-over function is controlled by "Enable 1" , "PGOOD 1" and V5SW should be higher than  4.7V.  Could you confirm any side effect when Vout2 connect to V5SW ? Can we only use the internal LDO  without the switch over function? 

  • 0
    TI__Mastermind 27470 points
    Hi Mike :
    below is my concern:
    when 12Vo1 is on, but 5Vo2 is off and its loading is still on , V5SW and VREG5 may pull lower by 5Vo2 loading current.

    so you should make sure when Enable 1 is high an PGOOD1 indicated good, 5V is already there.

    Thanks

    Daniel
  • 0
    TI__Expert 6425 points

    Hi Mike, 

    1, you can use the internal LDO without the switch over function. You just need to float V5SW. 

    2, if you connect V5SW with Vout2, when EN1 is high, and at this time Vout2 is off, switch over function couldn't be triggered. if you combine EN1 and EN2, switch over function is no problem. 

    Best Regards,

    Edwin. 

  • 0 in reply to Edwin Zang
    Intellectual 730 points

    Dear Sir,

    My name is Alec who support Mike for the TPS51220A power design. Baisc on your suggesiton, here are our undertasnig after few discussing. Please kindly help us confirm the items as below and give us your comment.

    1. If we could make sure EN2 pin is always enabled before EN1 enabled(meaning 5VSB will be ready before 12V is enable). Will the currently design be ok to use?

    2. Assume item 1 is confimred. When CH2(5VSB) have protection(OCP. OVP. UVP) occured , 5VSB will be off. and it woudl also turn off another CH(12V) based on TPS51220A spec. is that correct?

    Above, please kinldy hlep us confimed those two items. thank in advance

    Alec Chen

  • 0 in reply to Alec Chen
    TI__Expert 6425 points

    Hi Alec, 

    1, Yes, it's ok. 

    2, yes, it's right. 

    Best Regards. 

    Edwin.