BQ24074: CHG pin promble

Hi Denny,

To narrow down the issue, is it possible to isolate the battery charger from the gauge? CAn you also verify the connection between the battery and the charger? Outside of the abnormal behavior for 60ms, the noise on the BC_BAT and CHRG_OK signal is more than expected. Is it possible to zoom in on the noise as it is more prominent when the behavior is being seen?

Best Regards,

Anthony Pham

Hi Anthony

Thanks for your feedback, the circuitry please refer to the attached file, And I try to cutting the load both charger output(U2_Pin10,11) and BAT output(U2_Ping2,3) Monitor the signal with USB_5V, BC_BAT, CHRG_OK with remove each components.

6011.2021-04-21-A7.pdf

After remove all the related parts, the noise looks smaller but the abnormal width still 60msec and drop low, have any comment here?

BTW, with the TEST3, here only block the loading for charger output(U2_Pin10,11), even get 60msec on BC_BAT but the CHRG_OK keep low here, that means LED will light.

If you have any comment in advanced please let me know, many thanks!!

Yellow line : USB_5V

Green line : BC_BAT

Blue line :  CHRG_OK

Test 1：original testing

Test 2：remove R8

Test 3：remove R8、R24

Test 4：remove R8、R24、R10

Test 5：remove R8、R24、R10、C2、R4、R7

Hi Denny,

Taking a closer look at the schematic, it looks like you don't have the recommended capacitor on the BAT pin. Can you increase the capacitance to the required range (4.7uF to 47uF)?

Best Regards,

Anthony Pham

Hi Anthony

Sorry for missing this result, add to capacitance(47uF) on BAT pin, please refer to the below graph.

The raising/falling time looks a little change but still get abnormal waveform.

Have any comment of this issue, we still gating on this problem.

Or need some waveform and other information?

Many thanks

Denny

HI Denny,

I've reserved some lab time to look at this more closely tomorrow.

Best Regards,

Anthony Pham

Hi Denny,

The 60ms could potentially be a recovery time from a short circuit on the output. Would you be able to provide a waveform of the output as well? Just to be sure, this is with the battery connected directly to the BQ24074 and not to the gauge IC?

Best Regards,

Anthony Pham

Hi Anthony

Here you are, if need to check other point please let me know and share some comment for further analysis, thanks!!                       

Yellow : USB_5V

Green：BC_BAT (Battery)

Blue：BC_BAT# (OUT)

1. V780B BC_BAT Normal sample

2. V780B BC_BAT Abnormal sample

Many thanks

Denny

Hi Denny,

Is the BAT capacitor still within range or is it still according to the schematic?

Is it possible to measure the CURRENT waveform at IN, OUT, and BAT while also showing the BAT voltage waveform? I don't see any issues based on the voltage at the OUT. Is it also possible to check the resistance at ISET and ILIM pins?

As this isn't typical, the /CHG is high impedance temporarily before shorts are checked for. I'd like to see where exactly in the startup this is occurring. It'd also be great to if you could shift the startup to the left so that the 0s is where the -2s marker is.

Is it also possible to test this at different battery voltages? I have a suspicion this may be the battery detection routine occurring as it is low for about 250ms which is about how long the battery detection can occur. 

Thanks for being patient and best regards,

Anthony Pham

Hi Anthony

The customer's reply as below.

Is the BAT capacitor still within range or is it still according to the schematic?

This 2 are new battery pack, so the cap. value is same as schematic , So I will capture the waveform with 10uF today. <= Due to the footprint of 10uF is 0402 and it’s fit on our PCBA, 47uF is only 0603 package…if you have concern please let me know.

Is it possible to measure the CURRENT waveform at IN, OUT, and BAT while also showing the BAT voltage waveform? I don't see any issues based on the voltage at the OUT. Is it also possible to check the resistance at ISET and ILIM pins?

I can measure the CURRENT waveform but only one channel, I will check the current probe status later and not problem of showed both current & voltage.

             Regarding to ISET , ILIM

Resistor of ISET, recommend range is 590ohm to 8.9Kohm ~ our PCBA used 590 +/- 1%... that I will try the big one 650 ~ 1K ohm resistor and observe the waveform.

Resistor of ILIM, recommend range is 1.1Kohm to 8Kohm ~ our PCBA used 1.1K +/- 1%... that I will try the big one 1.2K ~ 2K ohm resistor and observe the waveform.

As this isn't typical, the /CHG is high impedance temporarily before shorts are checked for. I'd like to see where exactly in the startup this is occurring. It'd also be great to if you could shift the startup to the left so that the 0s is where the -2s marker is.

No problem of our oscilloscope, I can set up for monitor the +/- 2.5sec, but the graph I provide before is already use this setting, if no problem of this setting, I will capture the /CHG waveform to you.

Is it also possible to test this at different battery voltages? I have a suspicion this may be the battery detection routine occurring as it is low for about 250ms which is about how long the battery detection can occur.

This one is a little confuse to me, because this problem is happen with shipping mode, this mode means the MOSFET are off state.

After plug-in, the abnormal waveform is appears before MOSFET turn on and also list below 2 items for reference

• According the previous testing, even we cut off the loading both OUT , BAT the abnormal waveform still exist.
• We use only one battery for testing the voltage is around 3.6V, the good PCBA still have normal result but bad PCBA still have this abnormal waveform.

 Thanks for your remind, I will check all the cap. resistors are fit the datasheet range and let you know the value!!

Update for 1^st item, the capacitor change 10uF, thanks!

1. V780B BC_BAT Pass sample (Change C15_10uF/0402)

2.V780B BC_BAT Fail sample (Change C15_10uF/0402)

Hi Denny, 

Denny Huang said:

This one is a little confuse to me, because this problem is happen with shipping mode, this mode means the MOSFET are off state.

Neither the BQ24074 or the BQ28Z610-R1 have ship mode. Are you referring to the system? 

If the FETS are off on the BQ28Z610 and the BQ24074 is not seeing a battery, this sounds like the battery detection routine. If the test is conducted on the board with abnormal behavior with a lower battery voltage, you may see the the voltage drop to the true battery voltage. 

Denny Huang said:

No problem of our oscilloscope, I can set up for monitor the +/- 2.5sec, but the graph I provide before is already use this setting, if no problem of this setting, I will capture the /CHG waveform to you.

I just wanted to see more of the waveform after the device had turned on. This isn't required. 

Denny Huang said:

I can measure the CURRENT waveform but only one channel, I will check the current probe status later and not problem of showed both current & voltage.

If you're able to show the current waveforms of each in individual images this is also fine.

Best Regards,

Anthony Pham

Hi Anthony

The customer's reply as below.

Neither the BQ24074 or the BQ28Z610-R1 have ship mode. Are you referring to the system? 

If the FETS are off on the BQ28Z610 and the BQ24074 is not seeing a battery, this sounds like the battery detection routine. If the test is conducted on the board with abnormal behavior with a lower battery voltage, you may see the the voltage drop to the true battery voltage. 

The customer feedback:

The definition of battery pack is let gas gauge turn off the MOSFET, our product will connect to the system(doorbell) if w/o turn off the MOSFET will cause very high standby current.

You are right, the BQ28Z610&BQ24074 are not seeing a battery … it’s need to plug-in 5V USB to turn on the MOSFET(like you said, detection routine) <= this action called “wakeup from ship mode”

Normal waveform(Charger_BAT) : with “wakeup from ship mode”, the LED indicator are correct, both Green & Red LED are light.

Abnormal waveform(Charger_BAT) : with “wakeup from ship mode”, the LED indicator are not correct, only Green LED light <= it’s looks detection routing have some problem

So, refer to this clue, I want to know why some charger have abnormal waveform, refer to previous DOE, even cut-off all the loading of charger, the waveform still incorrect.

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Due to current PCB layout can’t cut for BC_BAT(Pin2,3) measuring, so only set the current probe on IN / Out individually.

Yellow : IN (USB_5V) voltage

Green : BAT (BC_BAT) voltage

Blue : OUT (BC_BAT#) voltage

Red : current probe

5V input current(Pin13)

Charger output (Pin10,11)

Many thanks

Denny

Hi Denny,

Based on these waveforms, I believe what the customer is calling abnormal behavior is simply the battery detection routine. This is an automatic process done by the device whenever a battery is not present/connected. 

Denny Huang said:

The definition of battery pack is let gas gauge turn off the MOSFET

Denny Huang said:

it’s need to plug-in 5V USB to turn on the MOSFET

The customer has described the FETs (I assume on the BQ28Z610-R1) to be a factor in connecting the battery to the charger. So let's investigate this further. Can we get a waveform showing the voltage at the following pins:

• CHG on the BQ28Z610-R1
• VBAT on the BQ24074
• VIN on the BQ24074
• /CHG pin on the BQ24074

And can we also try with different battery voltages?

Best Regards,

Anthony Pham

Hi Anthony

The customer's reply as below.

No problem of waveform capture, just clarify some setting in details, thanks!!

1. CHG on the BQ2828Z610-R1 <= please refer to the below partial circuitry, is this the correct location(red circle)?
2. Regarding to various battery voltage, I propose to 3.6V(30%) & 4V(80%), I will prepare the 2 kinds of battery.
3. I will take the new one abnormal sample for signal capture, if some parts need to change please let me know.

Many thanks

Denny

The customer's reply as below.

One more clue for your reference, I try to reduce the loading of BC_BAT.

So I remove C7  and I found the LED behavior become normal.

But I can not remove all the capacitor and it’s just only one PCBA result. Just for reference, thanks!!

Many thanks

Denny

Dear team

 The measuring result please refer to the below

 And one more thing want to let you know that I have 5pcs testing with various capacitor of OUT.

Big capacitor will have /CHG incorrect behavior.

Less capacitor will become normal.              

But recommend capacitor range of OUT is 4.7uF ~ 47uF but 47uF will get this problem.

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Yellow : VIN (USB_5V) voltage

Green : BAT (BC_BAT) voltage

Blue : /CHG pin on the BQ24074 voltage

Red : CHG on the BQ28Z610-R1

Battery 3.65V

Battery 4.11V

Many thanks 

Denny

Hi Anthony

The customer's reply as below.

Thanks for your comment, one problem here, what’s the BQStudio and how to use it to gather the log?

Anthony said : “connect the BQ28Z610-R1 to BQStudio and gather a log during the startup process”

Many thanks

Denny