BQ24092: TS specification

Hi Fred,

I'd like to try and do the same thing we do with the BQ2407X family where we use a series and parallel resistor to shift the resistance seen without needing to use active components. Before I proceed, I'd like to confirm that the customer the temperature thresholds that the customer would like. Is it 15C for cold and 45C for hot?

Best Regards,

Anthony Pham

Hi

yes, i think so, 

please see below their spec

thanks

Hi Fred,

Awesome, I'll go ahead and look at some possible solutions for this.

Best Regards,

Anthony Pham

thanks 

please set this as priority, thanks

Hi Fred,

It looks like a passive idea may not work and so if the customer is ok using the active solution they have, it will be better. But from my calculations, it doesn't look to be correct. 

If they leave the voltage divider the same for the comparator and it is a 0.5V at the inverting input, they will trip at 6.3 C instead of the desired 15C. From my calculations, it looks like the 3.24k needs to be about 9.5k to work at 15C. 

At the moment, they are also tripping at about 41C. Is this ok?

Best Regards,

Anthony Pham

Hi Anthony,

so this active solution is feasible, I'll tell them to proceed.

and why we need to change to 9.5k , would you elaborate with equation?

734mV+50uAx9.5kohm=1.21V, but the 10C threshold is 790mV. (not match)

I'm not sure if I calculate wrong, please provide your equation and let me know where I'm wrong

2. about tripping at 41C, do you suggest change another NTC with closer one?

Hi Fred,

Ah I see, I misread and thought 15C was desired as cold cutoff. Let me re-examine this. 

Best Regards,

Anthony Pham

Hi Anthony,

thanks,

please help on this

Hi Anthony,

what should we adjust to set it exactly at 15C,

would you show the equation?

Hi Fred,

Let me work on a few slides and then send them to you.

Best Regards,

Anthony Pham

Hi Anthony,

I appreciate your support,

 you did mention right now value can't meet their spec,

but would you also guide us where where can change since I didn't see it in the slide.

 change another NTC? change resistor? 

Hi Fred,

Is it possible to change the NTC? Is it possible to change the charger (power path vs non power path)? 

Best Regards,

Anthony Pham

Hi Anthony,

I think they can change NTC to meet the spec,

but i'm curious how does this has anything to do with the charger (power path)?

Hi Fred,

0 to 45C for hot / cold threshold can be difficult with how the TS monitoring works. From what I remember, we don't have any non power path chargers (I'll double check) that can be adjusted to 0 - 45C but we have some power path chargers that can.

Fred Cheng said:

I think they can change NTC to meet the spec,

I'll see if this possible

Best Regards,

Anth ony Pham

Hi Anthony,

I'm confused, 

as the report shown , the beta=3370 can't meet all the threshold perfectly whether 15C or 45C.

my question is why did these threshold in datasheet marked with a specific temperature while we still need a specific NTC to meet it perfectly. (obviously beta 3370 can't)

Hi Anthony,

my question is they did use 10k and beta=3370 NTC now,

but why 45C threshold now is not matched but 41.23C ?

when above 25C, the MOS hasn't turn on , should have matched ideally?

Hey Fred,

I went and check on an EVM and I can confirm that the datasheet voltage threshold is correct. I'll check and see what the reason is for saying it's 45C. 

Best Regards,

Anthony Pham

then the only reason is 

customer calculate wrong on this, please help check if it is what I say.

Hi Fred,

The 45C value for a Beta = 3370 10k NTC is about 4.92k. That is not miscalculated. 

Best Regards,

Anthony Pham

Hi Anthony,

my question is if NTC is what datasheet specified ,

then why the 45C threshold is not matched?

50uAx4.92k=246mV not equal to 278mV

Hi Fred,

I understand. I'm looking into this and so I appreciate your patience.

Best Regards,

Anthony Pham