BQ24092: Follow up question

Robert Whalley

Prodigy 200 points

Part Number: BQ24092
Other Parts Discussed in Thread: BQ24090,

Could you explain in more detail the following sentence from the related post's response?

"This could trigger near the CC / CV point with right resistance between battery and OUT pin"

In particular the significance of the resistance between the battery and the OUT pin.

Many thanks.

over 5 years ago

0 Bill Johns over 5 years ago

TI__Guru 68686 points

Hello
I reviewed the original post and your below comment is significant.
"Disconnecting the TS pin completely stops this behavior."

My guess is when you disconnect the TS pin / NTC you add a 10k resistor to ground to keep the unit operating.
The BQ24092 will change charge voltage and current near hot and cold termination points see figure 17 in data sheet. This is JEITA profile, note the BQ24090 does not have this.
Check the voltage on TS pin when the problem is occurring.
Normal charge is 790mV to 278mV.
Between 278mV and 178mV the charge voltage is reduced.
Between 790mV and 1230mV the charge current is reduced.
See page 9 of data sheet V-TS 0C, V-TS 10C, V-TS 45C and V-TS 60C.

0 Robert Whalley over 5 years ago in reply to Bill Johns

Prodigy 200 points

Hi,

To clarify - when I disconnect TS it is left floating, therefore, as I understand it, forcing TTDM mode and disabling TS monitoring. Does that change your answer?

I will definitely check the voltage on the TS pin when the problem happens as you suggest.

Many thanks,

Rob Whalley

0 Bill Johns over 5 years ago in reply to Robert Whalley

TI__Guru 68686 points

Hi
No does not change answer or area that we should look at.

0 Robert Whalley over 5 years ago in reply to Bill Johns

Prodigy 200 points

I have measured the voltage on the TS whilst the charge current is fluctuating by about 50mA, in pulses that are 30ms wide, and it is 0.435V. That seems to be in the middle of the normal range. What is that telling us?

0 Bill Johns over 5 years ago in reply to Robert Whalley

TI__Guru 68686 points

Voltage look about right for the NTC. In TTDM mode works OK and in this mode the device does not terminate charge.
Try connecting the TS pin to ground with a 10k resistor.
This will rule on misbehavior of the battery pack NTC.

Do you have a scope capture of the voltage at OUT vs Current at OUT pin?
Can you send schematic of circuit?

0 Robert Whalley over 5 years ago in reply to Bill Johns

Prodigy 200 points

I'll pull the TS pin down with 10K as you suggest, and I'm happy to send a schematic of the circuit, but not on this forum because it is confidential. If you could advise how to send it to you directly, that would be great.

0 Bill Johns over 5 years ago in reply to Robert Whalley

TI__Guru 68686 points

We are working this problem using conversation feature of Forum off-line and will close post.

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BQ24092: Follow up question