TPS23525: Design Calculator

Hi Sriman,

Can you share application details and system requirements. ? Do you need to support load during input power fail ? If yes, you need to use Cbulk to support the load.

For this high power design, you need to use both Q1 and Q2 MOSFETs. Q1 should have strong SOA and Q2 parallel FETs support low Ron in steady state. Please refer app note for more details https://www.ti.com/lit/an/slvae07/slvae07.pdf

I have attached the design sheet with FET details. Let me know if you have any follow-up questions.

TPS2352X_Excel_Tool_Web_RevB_modified.xlsx

Best Regards, Rakesh

Hi, 

We are planning to give dual input (-48V_A and -48V_B) to the system. It has to go through this OR'ing controller and the output will be given to DC-DC converter. In case of power failure, our system has to support only some part of the load for small duration of time, like dying gasp event.

1. In the calculator/data sheet, Q1 and Q2 MOSFETs  can be used in 23521 and 23523. But both of them do not perform dual oring. So we have to use TPS23525. Will that MOSFET Q1 is alone sufficient  for that high power(1200W)?

2. As I mentioned our system should support some part of the load during the input power fail. Can we get any details on calculations related to Cbulk and time to hold the charge for few seconds.

3. The calculator is mainly focusing on hotswap. We are also concerned about dual oring. Is there any special calculator for TPS23525 not like TPS2352x. 

Thanks

Hi Sriman,

1A. For TPS23525, GATE2 is not available. You would need more number of MOSFETs in parallel for Q1 to keep it Tj within the practical limits. I prefer Tj of 100C for long term reliability.

2A. Please unlock the design tool with TPS2352X and unhide the sheets to view the background calculations.

3A.ORing FET selection is mainly of the power loss and reverse current cut-off. Please refer Section "10.1.1.2.2 MOSFET Selection in www.ti.com/.../lm74700-q1.pdf" for more details.

Best Regards, Rakesh

Hi,

Thanks for the reply......

I have gone through your suggestions. In LM74700-q1,  I had seen section 10.2 where it explains about ORing solution. Can that be used for -48V application?? (Reverse ploarity). Is it intended only for positive supplies??  (Because I couldn't see any RTN path.)

Thanks