BQ27426: Check on coeff for NTC ERTJ0ER103J

Hello Sepeedah,

I'll need to check the internal structure of the bq27426 if it's the same as the excel sheet, that excel sheet is designed for some of the older platforms and may not correlate correctly.

I'll try to have a better answer tomorrow.

Sincerely,

Wyatt Keller

Hello Sepeedah,

I'm still waiting to hear from someone else on the team. The fastest was would be to upload the coefficients calculated, if they're not correlating with the right voltages the internal structure is most likely different and will need to modify the excel sheet.

Sincerely,

Wyatt Keller

Thanks Wyatt for continuing to check on this.

Can you please explain more on the method of checking? Which register would correlate to TS voltage to read? I think that's what you are referring to, but not sure where to read that from, is there a register to read? Also, I see we need to set an offset value as well. Would this be the same value as 'adp' indicated in the excel sheet? I think would help a lot if we can get confirmation if the calculator is the right one. If not, please let me know how we can get the correct values. Thanks!

Hello Sepeedah,

By checking the temperature reported vs the actual temperature will indicate how well the polyfit worked. This will be the best way to make sure the excel is correct because I can't confirm the temperatures calculated using the lab. There's not a direct way to measure the voltage on the TS pin.

We really recommend using the NTC 103AT because calculating new coefficients can be challenging to get the same accuracy, or any accuracy with different Beta value from the 103AT.

Sincerely,

Wyatt Keller

Thanks Wyatt. I understand the preference to use 103AT, however as I mentioned in the first post, customer can NOT accommodate the size for their design, so they have to pick a smaller NTC. 

Let's focus on making sure we provide the correct calculator for the customer, we haven't confirmed that still look like. Can we get that please? Also following to my previous question, is the offset value the same as 'adp' value in the excel sheet (if that is the correct calculator)?

Thanks Wyatt! Just to make sure, matching beta, resistance, and the respective tolerances should be all that we need to check, right? Customer is needing 0402 package. I've filtered out this list based on what matches with 103AT parameters for customer to take a look and test out. Let me know in case there is anything else we need to consider.

Sounds good, thanks!