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TPS2459 Hot Swap

Ankit Kumar
Prodigy 160 points
Other Parts Discussed in Thread: TPS2459, TPS2359

Dear Sir,

In my design, there is a I2C backplane and 16 number of cards. Among these 16 cards, there are 12 general purpose I2C cards, dual redundant Power supply cards and dual redundant controller cards. Before each slot on backplane, i am using TPS2459 whose inrush current limit, operating current limit and other parameters can be set using I2C bus

But i am facing one problem as follows:

The controller card can control the TPS2459 using I2C bus and take care of the 12 general purpose I2C card and Power supply card slots. 

"But for the controller card hot swap, I will not have access to the I2C bus itself.  How to take care of inrush current and other parameters of controller card's power hot swap. 

And could you please also tell me the minimum operating current that i can  have for 12V channel of TPS2459.

Thank you

  • 0
    Prodigy 160 points

    What i have thought is as follows:

    I will use a 2:1 master selector IC (PCA9541) and connect both the controller cards on I2C bus to this IC. This IC receives I2C lines from both the controller and routs only one

    I2C bus at output. 

    " Suppose if one controller card is removed or inserted to backplane, other controller card will take care of the inrush currents, operating current limits by controlling TPS2459 at the slot of card being inserted"

    Please tell me whether it will be ok to do like this.

    thank you,

    ankit

  • 0 in reply to Ankit Kumar
    TI__Mastermind 42795 points

    Your method seems to be sound. TPS2359 must be configured via the I2C bus.

     

  • 0 in reply to Eric Wright
    Prodigy 160 points

    Thanks a lot for the confirmation. 

    Could you please tell me, the minimum operating current for 12V channel. There is no information in datasheet. I am planning to have the following design parameters for 12V channel:

    12V CHANNEL: 

    • RSENSE = 0.005 OHM 
    • RSUM = 6180 OHM 
    • OPERATIONAL CURRENT LIMIT = 250mA.

    I am going to set operating current limit as 5% of the inrush current limit. SO

    • INRUSH CURRENT LIMIT *0.05 = OPERATIONAL CURRENT LIMIT. 

    (implemented by having  R3 FIRST BIT SET) 

    • SO INRUSH CURRENT LIMIT = 250/0.05mA = 5A 
    • So RSET = (5*0.005*6180)/ 0.675 = 230 OHM
    I request you to verify.
  • 0 in reply to Ankit Kumar
    TI__Mastermind 42795 points

    Your settings look good. There is no minimum 12V channel current (ie you can operate the channel with no load)

  • 0 in reply to Eric Wright
    Prodigy 160 points

    Dear Eric Wright,

    Thanks a lot for your confirmation.