TPS2456A: MOSFET Q6 in our hot swap circuit will be damaged (become short between drain and source ) on some boards

Hi Qianshu,

Welcome to E2E !!!

We will review the design and get back to you by tomorrow. 

Hi Qianshu,

Sorry for the delay in getting back to you. I will get back to you by Monday.

According to the schematic,

I_LIMIT = 23.4 A and t_FAULT = 6.4 ms. 

Using the SOA plot from SiRA00DP datasheet.

There is not enough SOA margin, which is the reason for MOSFET burn during short circuit at output. 

Please follow the "DESIGN EXAMPLE: CURRENT LIMITED START-UP" presented in the datasheet and rectify your schematic. Otherwise, if you share all the design parameters used in that above design example, I can calculate and tell you the appropriate values of the required components. 

Hi Avishek,

Thanks very much for your reply.  I have further questions below.

1. Which parameters should I share for you to help calculate and provide me the appropriate values of the required components?  Cout=1700uf/25V, maximum operation current is 15A on the main board.  There are two power supply modules in the system, each can provide up to 12.2V/61A.  There are 2 other cards (we call them IO cards), each has 15A maximum operation current.  There are two fans, each has 6.8A maximum operation current.  Can you help to provide the appropriate values of the required components for the main board?

2. I see there is a 100ohm serial resistor on the gate signals.  Is it too big?  How to get 0.5A to 1A sinking current when fast turn off with the 100ohm resistor?

3.  We have another product whose maximum operation current is 55A on main board.  There are two power supplies, each can provide 12.2V/90A.  The power supply modules are pluggable, but the main board is not pluggable.  Can we use TPS2456A to achieve the 12.2V power protect and oring function on the main board?  If yes, can you help to provide the detailed solution?  If not, can you propose other solution?

Best regards,

Qianshu

Hi Qianshu,

Please could you have look at TPS25985. I feel that TPS25985 is most suitable part for your application. 

TPS25985x 4.5 V – 16 V, 0.59-mΩ, 80-A Stackable eFuse with Accurate and Fast Current Monitor datasheet (Rev. A) (ti.com)

Hi Avishek,

TPS25985 is for my above question 3, right?  Can it achieve the oring function from the two power supplies?

I'm also looking forward to your answer to my question 1 and 2. 

Best regards,

Qianshu

TI device schematics.pdf

The complete schematics for my question 1 and 2 are attached.

Hi Avishek,

For my question 3, I think we only need the over current protect, short-circuits protect and oring function.  We don't need the inrush current limitation function since the board is not pluggable. only the PSU (power supply units) are pluggable.  It looks TPS25985 not a suitable solution.

Best regards,

Qianshu

Hi Qianshu,

Thanks for your feedback. I will get back to you tomorrow. For point 3, you may look into TPS24740. 

Hi Avishek,

Is there any update?

Best regards,

Qianshu