BQ24040: PMIC Charging Issue

Hi,

We can continue discussion here, what seems to be the issue you are seeing.

Thanks,

Nick

Hi Nick,

If you review complaint CS0433712, you will see that I am getting customer complaints for battery charging issues. I provided plots and schematics in that complaint. So as a follow on, Anthony P Pham suggested I remove the regulator from the the PCBA.

Here are the plots I captured:

1. Customer Complaint Controller with no alteration to the PCBA ( Regulator in place)

The time between Power_Good and Charge_Indicator going low is approx 2ms.

As you can see from the plot, the battery current goes back to zero,  before charge indicator goes low. The time interval between Power_good and battery current going to 0mA, is approx 1.6mS and it stays 0mA for about 0.4mS. The battery current is approx. 290mA.

2. Controller with no alteration to the PCBA and no customer complaint (Good Controller)

As seen in this image, the current stays at 290mA after Power_Good goes low and it doesn't change.

3. The Customer Complaint Controller used in Point 1 with the regulator removed.

The regulator was removed and the battery current is the same as in Point 1. We could not capture Power good or charge indicator in this plot due to the regulator being removed and disconnecting the power to our controller.

Can you please provide feedback

Thanks and Kind Regards

Hello,

I'm not able to access dropbox at work, can you attach the schematics here.

Thanks,

Nick

HI Nick,

Here is the schematic.

Thanks Aileen

Hello Aileen,

Recommend adding a 1uF input cap on the IN pin, C15 being placed before the FET may be causing some stability issues.

The flickering you are seeing on startup could also be part of the battery detect routine. This is done by charging battery for 25ms followed  by sinking current for another 25ms, you can read more in section 8.4.12 of d/s.

What is the voltage on TS pin during these tests?

Best regards,

Nick

Hi Nick, 

Thank you for replying.

I have reviewed the battery detect routine and I have a few questions:

• Does the PMIC start sinking current at the BATT_DETECT part of the flow chart?
• What is the sink current value? Is it the fast charge current value?
• In the flow chart, what does RETURN TO FLOW mean in all 3 cases that it is mentioned?
• What should the Vout state of PMIC be in the flow chart if
  
  • the battery is present
  • the battery isn't present
• In the flow chart OUT_REG is set to VREG -400mV. If the battery is absent and it starts the flow again, is OUT_REG reset and if so to what?

Thanks and Kind Regards

Aileen

Hi Aileen,

1. BQ24040 will alternative between charging at the fast charge value and sinking current every 25ms until IC has determined whether battery is present
2. Sinking current is IBD-SINK, 6-10mA
3. IC has determined battery present/ not present
4. The battery detect routine can run multiple times depending on the battery voltage, pin capacitance, and resistance between IC and battery
5. OUT_reg can either be VREG or VREG-400mV

Best regards,

Nick

Hi Nick,

Thanks for your feedback. 

If the battery is not present, what is the voltage at the out pin when the PMIC is alternating between IBD-SINK and fast charge current.?

Thanks and Regards

Aileen

Hello Aileen,

When battery is absent you will see battery detect routine waveform, this is a square wave between 3.8-4.2V. Example is given in Figure 9-9.

BR,

Nick