BQ25883: Is this right Chip for this project.

Dear Amir,

This part regulates the SYS pin to the minimum system voltage when the battery is depleted. Once the battery reaches this voltage, the voltage of the SYS pin is just the voltage of the battery plus the VDS of the BATFET. So if your battery was charging around 7.2 V, the SYS pin would not be able to be 6 V. This architecture is the NVDC architecture and allows the user to have a powered system with a depleted battery.

To help me better recommend a part, what is the application that requires a 6 V output with a 7.2 V battery?

Thanks,

Mike Emanuel

Please click "This resolved my issue" button if this post answers your question.

Hi Mike,

Thanks for the reply. The way my system works is :

1. I need to run a 6V pump (50mA).

2. I regulate 6v to 4.2v for the rest of my devices. (50mA)

Thank you

Amir,

The NVDC architecture is helpful for dealing with a depleted battery. I would highly recommend using this if you want an instant on feature. However, as such your output on the SYS pin will not be the 6V or 4.2V you are looking for. To achieve these voltages, I would recommend looking at TI's LDO regulators for the current levels you are talking about.

Just make sure that the drop across the LDO is small enough from the MIN_SYS setting (the lowest is 6.0 V but I would not recommend using this for your application) to achieve the 6V you are looking for. For example, if you set MIN_SYS to 6V and the LDO drops 0.5 V, your LDO for the 6V rail might only put out 5.5 V. Make enough margin from MIN_SYS to the output of the LDO to allow for your desired voltages.

Thanks,

Mike Emanuel

Hi Mike,

Once again thanks for the quick answer.  Since you do not recommend this ic for my project, do you have any recomandation.  My plan is to use an LDO regulator to convert 6V from switching regulator to 4.2V.

I even check with pump manufacture and they said the pump will work between 5-8v so I can use the battery voltage for the pump and use any regulator for my 4.2V.

Thank you

Amir,

I am confused as to your question. Could you please clarify?

Thanks,

Mike Emanuel

Sorry for the confusion, 

If you do not suggest this chip, do you have any other chip that you can introduce to me?

Thank you

I suggest this chip for the power path feature. You can couple the SYS output with LDOs to achieve the output voltages you want while still achieving instant system on with a depleted battery.

I also still do not understand what your required system voltages are and if you could further clarify that would be helpful.

Thanks,

Mike Emanuel

Please click "This resolved my issue" button if this post answers your question.

Sorry for the confusion:

Below is my voltage requirements:

1. Main circuit board need 4.2V  (I am planning to use LDO regulator for this)

2. the pump need 6V 50mA 

3. The battery is pre-pack:  2 series and 2 parallel Lithium-ion. Total voltage 7.2V 4.8AH 

Need to able to charge and manage the battery. 

Thank you