CSD87335Q3D: CSD87330Q3D,CSD87335Q3D

Sajna K

Part Number: CSD87335Q3D
Other Parts Discussed in Thread: TPS51285A, CSD87330Q3D,

i have designed a 3.3V/5V converter using TPS51285A.

i have selected CSD87330Q3D for the design. input voltage is 8.4V -12.6V. output current is 15A. OCP value set as 18A. Inductor selected is 1.2uH .

Now i have come across the part CSD87335Q3D. I would like to use this part instead of CSD87330Q3D.

For my new design ,output current changes to 18A. OCP will be 20A. Can i use this new IC as drop in replacement?

if i need to change the components , can you share me any excel tool for the calculation.?

over 5 years ago

0 John Wallace1 over 5 years ago

TI__Mastermind 33855 points

Hi Sajna,

Thanks for the questions. The two power block devices, CSD87330Q3D and CSD87335Q3D, are pin-to-pin compatible parts. The CSD87335Q3D has lower rds(on) MOSFETs than the CSD87330Q3D. I will forward this request to the applications team for the TPS51285A controller to help you with any changes necessary to accommodate the CSD87335Q3D.

0 Sam(MPAA) Zhang over 5 years ago

TI__Mastermind 19080 points

Hi Sajna,

OCP limit in your design is going to be 20A. In TPS51285, the OCP limit is set by valley inductor current, which means the current flowing through the FET can be higher than 20A. CSD87330Q3D max operation current is 20A according to the datasheet.

So replace CSD87335 with CSD87330 is not safe here.

Regards,

Hao

0 Sajna K over 5 years ago in reply to Sam(MPAA) Zhang

Prodigy 190 points

Hi Hao,

Thank you for your reply.

There is a miss understanding.

I want to replace CSD87330 with CSD87335.

if i increase my load current from 15A to 18A, and OCP changes from 18A to 20A

1.can i use CSD87335 instead of CSD87330?

2.do i need to change my inductor value?

0 Sajna K over 5 years ago in reply to John Wallace1

Prodigy 190 points

Thank you John.

Expecting a quick reply from the team.

0 Sam(MPAA) Zhang over 5 years ago in reply to Sajna K

TI__Mastermind 19080 points

Hi Sajna,

OK, I got your point...

1. Yes, CSD87335 is good for you.

2. No need to change your inductor value if only MOSFET is changed. Just pay attention that the saturation current and rated Irms should be enough for the higher current design.

Thanks!

Regards,

Hao

0 Sajna K over 5 years ago in reply to Sam(MPAA) Zhang

Prodigy 190 points

Hi Hao,

Thank you fro your reply.

However when i did the calculation , theoretically inductor value is changed according to load cuurent.

So you are telling practically , inductor value which is designed for 15A can be used for 18A of load if the DC current and saturation current of inductor is sufficient.?

0 Sajna K over 5 years ago in reply to John Wallace1

Prodigy 190 points

HI John,

any updates from the your application team.?

0 Sam(MPAA) Zhang over 5 years ago in reply to Sajna K

TI__Mastermind 19080 points

Hi Sajna,

Typically the inductor current ripple is recommended to be 0.2~0.4 of max loading current. This is the reason why you got a different inductance value from the equation when you input a higher loading current.

It's OK to keep the same indcutor here.

Regards,

Hao

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CSD87335Q3D: CSD87330Q3D,CSD87335Q3D