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LM25066A: LM25066A hotswap controller design verification

Ariharan S
Prodigy 60 points
Part Number: LM25066A
Other Parts Discussed in Thread: TPS25990, LM25066

We are planning to use the LM25066A in our design. We have selected primary components based on the design calculation sheet provided in the TI sheet and training videos. I am attaching the schematics and Design calculation sheet in the attachment. Kindly help me by providing review for the same. HOT_SWAP_CNTRL_REVIEW_DOCS.zip

  • 0
    TI__Mastermind 30915 points

    Hi Ariharan,

    Thanks for reaching out. I would like to propose our integrated eFuse solution here. I am sending you friend request here. Please accept that and then we will continue our discussion there.  

  • 0 in reply to Avishek Pal
    Prodigy 60 points

    Hi Avishek,

    sure, we can discuss. As of now, we prefer to go with the solution as we have almost finalised the design. Apart from the alternate suggestion, do you find any review comments with regards to the submitted part LM25066A.

  • 0
    TI__Intellectual 1450 points

    Hi Ariharan ,

    Many groups in Tejas started using Integrated FET  TPS25990  50A efuse with PMBus .  This will simplify your design . Please call me on 7022997629 ( Dilip.Mohol@ti.com)

    Dilip

  • 0 in reply to Dilip Namdeo Mohol
    Prodigy 60 points

    Hi Dilip,

    Thanks for the valuable suggestions and feedback. Unfortunately, we cannot go with the suggested part. Requesting you to help us with the review of the submitted part at the earliest. 

    Ariharan

  • 0 in reply to Ariharan S
    TI__Mastermind 30915 points

    Hi Ariharan,

    I will share the review comments by tonight. 

  • 0 in reply to Avishek Pal
    TI__Mastermind 30915 points

     Hi Ariharan,

    Please see the observations below. 

    1. Place a small capacitor, CIN (100nF to 1μF) directly adjacent to the VIN and GND pins of the LM25066 and COUT (1μF to 10μF) directly adjacent to the VOUT and GND pins to help minimize transients which may occur on the input supply line.
    2. R252 and C837 should be DNP.
    3. Schottky diode (SK153-TP or equivalent) needs to be placed at the output to clamp the output voltage from going too negative during short circuit events.
    4. Make R263 as 10Ω.
    5. The ground connections for the various components around the LM25066 should be connected directly to each other and to the LM25066's GND pin and then connected to the system ground at one point. Do not connect the various component grounds to each other through the high current ground line. For more details, see application note AN-2100.
    6. May I know the purpose of D1?
    7. Make R243 as 6.49kΩ to provide a bit more margin on the minimum power limit of 56W.
  • 0 in reply to Avishek Pal
    Prodigy 60 points

    Hi Avishek

    Did Schottky diode to be placed in the below mentioned place in schematics? 

  • 0 in reply to Ariharan S
    TI__Intellectual 1450 points

    Place Schottky diode (SK153-TP or equivalent) at the output as shown below. 

  • 0 in reply to Avishek Pal
    Prodigy 60 points

    Hi Avishek,

    Thanks for the response. We have implemented all the review comments except for this Schottky diode. Is it possible to proceed without having that diode, In PCB we don't have required space to accommodate the diode. 

  • 0 in reply to Ariharan S
    TI__Intellectual 1450 points

    Hi Ariharan,

    The purpose of the  Schottky diode is for LM25066   protection from negative voltage ( Device can only handle -0.3V). Purpose of TVS diode at Input is to protect LM25066 from positive high voltage. We recommend all designs with hot swap controller to have a TVS diode on the input and a Schottky diode at the output (for transients).

    Assume device Output Hot short condition :- 

    During short circuit condition/ Hot short  assume di/dt =(0A to 100A) /10nsec =-10¹°

    Assume trace inductance is 10nH

    Voltage across Inductor will be 10nH *(- 10¹°) =-100V .

    Assuming both inductive traces at input side and output side has 10nH inductance, will produce 100V  positive spike ( Input of device)  and negative spike ( Output of device) . This will damage device.

    So both TVD diode and Schottky diodes are recommended.  This voltage will vary based on trace inductance .( This issue may arise during Hot short condition)

    If there  is space  constrain, we always recommend to use TPS25990

     

     Regards

    Dilip