BQ25713: Adapter / Main does not come on Vsys in absence of Battery

Hi Dharin,

   There should be no issue with VSYSMIN regulation when there is no battery present, so expected behavior would be for you to observe accurate VSYSMIN. What is the value of the ChargeStatus Register you observe?

Dear Kedar, 

I have attached xls capturing the values of registers that we observed post writing into the certain registers. 

Attaching the same herewith for your reference again.

We also expected adapter supply to be appearing at Vsys but we are not observing the same and hence wondering where we would be wrong. 

Thanks

Dharin

6237.bq25713_i2c_write and read info updated .xlsx

Hi Dharin,

   The excel sheet does not contain the values of the ChargeStatus register (0x20 and 0x21). Can you read that register and show the values? Try flipping the charge inhibit bit as well.

Dear Kedar, 

Please find the attached updated xls capturing the charge status register 0x20 and 0x21. 

We will not be able to get any register status when only adapter is present as the output (Vsys) is below 1V and hence we can not run I2C and hence can not get any data. 

bq25713_i2c_write_and_read_info_updated_09Sep20.xlsx

Thanks

Dharin

Hi Dharin,

   Charge status register is showing in IINDPM which is interesting. When you power up (insert adapter) with just SYS present and battery absent, do you have a continuous load on SYS?

Dear Kedar, 

Could you please elaborate on "Charge Status register showing in IINDPM"?

The battery management is part of our entire hardware which is expected to auto start as soon as power supply is available. 

Thanks and warm regards

Dharin 

Hi Dharin,

   When I input the 0x20 and 0x21 values into charge status register it shows the IINDPM bit has tripped and charger is in IINDPM.

   Try these 2 steps in order:

1. Set CHRG_INHIBIT to 0, and retest powering up adapter with only SYS present
2. Power up With SYS_SHORT_DISABLE = 1
3. Power up with following sequence
   1. Before adapter plugs in, put the charger into HIZ mode. (either pull pin 6 ILIM_HIZ to ground, or set REG0x35[7] to 1)
   2. Set 0x00[2] to 0 to disable LDO mode.
   3. Set 0x30[0] to 0 to disable auto-wakeup mode.
   4. Check if battery voltage is properly programmed (REG0x05/04)
   5. Set pre-charge/charge current (REG0x03/02)
   6. Put the device out of HIZ mode. (Release ILIM_HIZ from ground and set REG0x35[7]=0)

Let me know results of testing.

Dear Kedar, 

Thank you for reply. I have some fundamental questions here.

When we turn off the supply, does BQ25713 store the last configured parameters like it having a Flash?

Because once powered down, I have no supply to be able to configure any register here. 

For example, you have mentioned to set certain registers, set certain signals.

But in absence of the device letting the input of Adapter pass to Vsys, I have no way to run the host to set the registers through I2C. 

Am I missing something here?

Thanks and warm regards

Dharin

Hi Dharin,

   BQ25713 does not have flash, and will reset to default values after POR. I was under the impression your I2C pullup was connected in a weird configuration due to this comment: 

"We will not be able to get any register status when only adapter is present as the output (Vsys) is below 1V and hence we can not run I2C and hence can not get any data."

When you insert the adapter, you will be able to program the registers, once I2C communication lines are pulled up. When only adapter is connected, and only VSYS present, you should be able to read the status of the I2C registers right? 

Did the other workarounds mentioned work? If not please also take a waveform capture of VBUS, VSYS, SW1 and SYS_LOAD on adapter insertion with just VSYS connected.

Dear Kedar, 

Our 3.3v pull up for I2C is generated from Vsys. If Vsys is not available, we will not get I2C. 

We were under the assumption that Vsys should come by default if Adapter input is present even if battery is absent. 

We will look into overall implementation and get back. 

Thanks

Dharin

Dear Kedar, 

Our current implementation has inherent assumption that if we start system with adapter connected and provides >10V supply, output Vsys will be available even if battery is not present. 

Ideally BQ25713 should do this considering that Vbus is available, VBAT is not available, REGN gives 6V. 

But we are not able to get Vsys in the above scenaro. 

We will not be able to load I2C or run our host system to support I2C loading if Vsys is not available. 

How do we support such scenario? Typically we expect device to support Vsys in absence of battery and presence of Adapter. 

Let me know if anything wrong from my end on this. 

Thanks and warm regards

Dharin

Dear Kedar, 

Could you please let us know what the expectation from BQ25713 side to get Vbus power appear to Vsys when battery is not present? 

We will not be able to access I2C as host processor is also dependent on Vsys to start the functioning. 

Thanks and warm regards

Dharin

Hi Dharin,

   VSYS should power up when VBUS is applied and be regulated at VSYSMIN without host intervention, when adapter is inserted with battery absent. Take a waveform capture of VBUS, SW1, VSYS and VBAT when input adapter is plugged. No SYS load should be present when doing the above test.