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TinySwitch-4 MTBF calculation

Posted by: tetsuya.nagai on Mon, 06/07/2021


I am designing power supply with TNY284P, and I would like to calculate MTBF according to MIL-HDBK-217F.

I can measure voltage/current/temperature, but I don't know which parameter I should use.

Please let me know how to proceed the prediction.

Thank you.


Submitted by PI-BERJ on Thu, 06/17/2021

Hi Nagai,

You can use the values declared on the Absolute Maximum Ratings page on the datasheet (see attached).


Attachment Size
absmax.png 166.13 KB

Thank you for your reply.

Do you mean I can calculate it as "MOSFET"?
How shall I consider control circuit block?

I thought it shall be calculated as "IC" + "MOSFET".

I can calculate "IC" part if I can identify C1 value on MIL-HDBK-217F handbook, sec. 5.1.

I appreciate if you can tell me more detail of calculation method or complexity of the device.

Thank you.

Submitted by PI-BERJ on Mon, 07/05/2021

HI Nagai,

You are right. It should be calculated as IC + MOSFET. I'll try to get in touch with the IC design guys and get back to you on this.


Submitted by PI-BERJ on Thu, 07/08/2021

Hi Nagai,

Unfortunately we can not disclose in a public forum the details regarding the aforementioned C1 value due to confidentiality. We can however send it to you by e-mail.

Please also check (attached) if the result from our reliability report may suffice for your needs.


Attachment Size
rel_report.png 29.07 KB
Submitted by tetsuya.nagai on Tue, 07/13/2021

Thank you for sharing FIT value of the item.

I think it is useful for calculate system MTBF.

I appreciate if you can also share more information regarding C1 value calculation.

My e-mail address is ""


Thank you in advance.


Best Regards,