BQ24074: BQ24074 charge query

Hi Star,

I don't believe thermal regulation will cause intermittent charging as seen in the log. I will need to be in the office to check if this occurs at 1.5A charging. Is there a load on the OUT pin that's taking current as well? 

I don't see any problems with the schematic or layout.

Best Regards,

Anthony Pham

Hi Anthony Pham

Thanks for your help. USB directly charges Vin (U2)+the battery uses BQ28Z610 for setting protection

Is there any protection will cause this problem？

Waiting for your reply.

Thanks

Star

Hi Star,

I don't believe so. This does not look to be the expected thermal regulation behavior. Is it possible to get a waveform of the battery current? It'll be easier to see compared to a log.

Best Regards,

Anthony Pham

hi Anthony,

The problem is not the max current.

The problem is the current could become 0A for 2+ sec while charging, as below oscilloscope plot.

What BQ24074 function could cause such behavior?

Hi Tzlu,

What is the yellow waveform? Is this battery voltage?

Let me try this in the lab with your settings and see if this could trigger some level of thermal regulation. 

Best Regards,

Anthony Pham

Hi Anthony Pham

Sorry for reply late.

CH1  =  charging voltage ( USB 5V )
CH2  =  charging current

Waiting for your reply.

Thanks

Star

Hi Star,

No worries. Does this occur with a lower charge current? What if the charge current is set for 500 mA?

Best Regards,

Anthony Pham

hi Anthony,

If the charging current is changed to 500mA, the phenomenon disappears, but this situation conflicts with customer needs.

To recap the current test conditions:
1. Change RT2 to 10K resistor, this state will be gone
2. Use the chamber to keep it at 25 degrees (blow the battery pack) and the state will disappear.

Hi Luke,

Understood, this does seem like it would be a battery temperature, thermal regulation, or possibly even a thermal shutdown behavior. The lower charge current will reduce the amount of power dissipated as heat and this could be the reason why changing it to 500mA removes the behavior.

Luke Yeh said:

Change RT2 to 10K resistor, this state will be gone

I see that RT2 goes to a node mentioned as TH1, does this go to the charger? I see on the BQ24074 side it becomes TH instead of TH1. 

Luke Yeh said:

. Use the chamber to keep it at 25 degrees (blow the battery pack) and the state will disappear.

Outside of the chamber, what is the TS voltage with the 1.5A charge current? If changing the RT2 to 10k (and RT2 goes to the BQ24074 TS pin) removes the behavior, I'm worried the battery temperature may be out of a valid range.

Best Regards,

Anthony Pham

hi Anthiny.

1. the Star feedback circuit TH is right, net name is TH ( at the layout rule need different name to changed TH1)

2. cell and charger log Temp is under the 50deg, at this time still trigger charger IC protection, see the attachment file.

3. can you suggest If by-pass BQ24074 thermal (change ot 10K/1% Resistor), and TEMP protection see BQ28Z610-R1 (set OTC in 55deg), have any design affect.

GA_5.15V_2022-12-20L.xlsx

hi Anthony,

In this case flow chart, we set two OTP protection :
BQ24074 follow HW contral OTP about 50deg. only for charging contral
BQ28Z610 is another temp protection contral EX :55deg in OTC.

so i think Temp is can be log it.

BR

Luke

Hi Luke,

I don't quite understand. It looks like with the NTC in place, it is showing signs of thermal protection either due to the battery temperature at the NTC or the IC temperature (although data shows it does not for both). What is the HW OTP you're referring to for the BQ24074 if you bypass the NTC with a 10k resistor? 

Best Regards,

Anthony Pham

hi Anthony,

1. BQ24074 HW OTP = charger suspend charging when the temperature is too high
2. The current situation affects the charging time (battery capacity=9.09Ah/charging time needs to be increased by 3hr~5hr)
3. If the charging temperature control of BQ24074 is changed to BQ28Z610, it should be able to avoid the phenomenon of charging stop

Hi Luke,

Luke Yeh said:

If the charging temperature control of BQ24074 is changed to BQ28Z610, it should be able to avoid the phenomenon of charging stop

Luke Yeh said:

BQ24074 HW OTP = charger suspend charging when the temperature is too high

Yes, this could be true.

My concern is that it cannot be distinguished at the moment whether it is an IC protection of a TS protection based on what I've seen over the forum so even if you remove the NTC, replace it with a 10k. If 50C or 55C is the cutoff based on the charger or the gauge, your log shows that this is occurring around 41C.

If you are changing to the 10k resistor instead of the NTC. The IC thermal protection may still occur if it is the IC that is entering thermal regulation or thermal shutdown. This control loop is separate from the battery temperature monitoring and is meant to protect the IC. It cannot be disabled.

Luke Yeh said:

The current situation affects the charging time (battery capacity=9.09Ah/charging time needs to be increased by 3hr~5hr)

This is quite the battery to be using a linear charger for. I'd greatly recommend that if charge time is a concern, using a switching charger such as the BQ25620 be used instead if time is a concern. 

Best Regards,

Anthony Pham