BQ25882: EN HIZ is set to 1

Sunny,

From the register data you provided I can see the Power Good status is showing as "Not Power Good." This generally points to a problem on the VBUS line. I would like to get some more information about your set up and some measurements.

• Does charging restart when the Enable HiZ bit is toggled?
• Do you have a transient system load on VSYS?
• What is the voltage of REGN before and after the fault?
• What is the VBUS voltage before and after the fault?

This will help me get a better idea of what the root cause of why HiZ enabled.

Thanks,

Ricardo

Hi Ricardo:

1.Does charging restart when the Enable HiZ bit is toggled?

No reboot

2.Do you have a transient system load on VSYS?

The test state is standby

3.What is the voltage of REGN before and after the fault?

Voltage before failure:  4.554V        After the failure: 5.07V

4.What is the VBUS voltage before and after the fault?

Voltage before failure: 5.056V         After the failure: 0.004V

Hi Ricardo:

Schematic diagram is as follows:

Sunny,

I have some immediate concerns looking at your schematic:

• Your schematic shows a 3 A system load and based on the register data you sent me I can see your minimum system voltage is equal to 6 V. You are exceeding your power balance:

5 V*2 A_max = 10 W < 18W = 6 V*3 A_max

If this is correct, I am wondering if your battery is supplementing your system load until it becomes depleted. Once depleted, it would be up to VBUS to supply the power to keep the system load satisfied. However, VBUS is unable to supply the necessary power and VBUS ultimately crashes. This crash could be the source of your Hi-Z status.

• I also have a concern that the capacitor you have placed between BTST and SW is too large. This capacitance should be 47 nF and you have placed a 470 nF capacitor.
• I would also recommend you place a 30 uF capacitor between PMID and GND to help reduce the voltage drop on a your adapter cable during current inrush.

Thanks,

Ricardo

Hi Ricardo:

We did the test and verification in standby state, and the system current is only 500mA, and the schematic diagram icon current is 3A, which is to meet the instantaneous current consumption during printing.We changed the capacitance between BTST and SW to 47nF according to your suggestion, and increased the capacitance between PMID and GND by 30uF.This does not change when tested in standby after the changes are made.Please give some Suggestions, thank you!

BR

Sunny

Sunny,

Today I recreated your setup on the EVM by loading the register data you gave me, connecting a battery, and applying a 500 mA load. After toggling the Hi-Z bit, charging immediately resumed.

Would be possible for you to bypass the charger on your board and use the EVM with the rest of the board?

Also, I am curious how you are powering the VBUS pin. If possible could you use a bench power supply?

Thanks,

Ricardo