TPS62086: Wrong output after a battery is drained and charged.

Hello Asael,

Thanks for reaching out, 

As of my understanding, your Vin is between 3.6 to 3.7 V and the desired output voltage is 3.3 V. If the input voltage is further dropped to 3.35 - 3.4 V. In this condition the difference between the Vin and Vout is 50 to 100 mV. Due to this there are certain possibilities that can happen in the device.

Condition 1:

If the total drop due to inductor DCR and H/S MOSFET Rds ON is less than 100 mV, then the device will operate in less than 100 % duty cycle and the desired output can be achieved.

Condition 2:

If the total drop due to inductor DCR and H/S MOSFET Rds ON is greater than 100 mV, then the device will operate in 100 % duty cycle making the H/S MOSFET always ON and the output voltage is not regulated.

Can you please provide me the schematic diagram with the inductor you are using and also, I would like to know the maximum output current for your application.

Please provide me waveforms of the input voltage at the device pin and output voltage for further analysis.

Thank you,

Regards,

Moheddin.

Hi Moheddin.

There is a confusion, sorry for that.

Voltage is from a cell; normal input is between 3.35V and 4.2V and we have 3.3V as output. 

Everything almost works well, because when the cell voltage is low, we sent the system to low power consumption,

but issue in rare cases is when the cell is fully drained. When we charge the battery without disconnect it, even if we charge the battery until 4.2 V, output voltage is between 2.1-2.4 V, not 3.3V. When this happens, we have 3.3V as output until we disconnect and connect the cell.

Not sure why this happens.

Hello Asael,

As the battery gets drain and the Vin reduces below Undervoltage lockout threshold, which is 2.2 V, the device shutdown. and it will start operating automatically once the Vin is above 2.2 V. Since your output voltage is 3.3 V, the device works as a regulator only when the Vin is above 3.3 V as mentioned in condition 1 and condition 2 in the above reply. But it looks strange in your condition. 

Can you please provide me the schematic diagram with the inductor you are using and also, I would like to know the maximum output current for your application.

Please provide me waveforms of the input voltage at the device pin and output voltage for your condition for further analysis.

Thank you,

Regards,

Moheddin.

I don't have the board now, but I will have it in some days. As soon as I and a teammate can check this, we will provide you the waveforms.

Hello Asael,

I will keep the threat open then, please provide me the data mentioned in the above reply once you received the board.

Thank you,

Regards,

Moheddin.

Hello Asael,

Any update regarding the waveforms.

Thank you,

Regards,

Moheddin.

Not yet Moheddin. Next week I hope we can test the board and send the waveforms.

Hello Asael,

Thank you for the update, I will keep the threat open.

Regards,

Moheddin.