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BQ25730: Can we Use BQ25730 Charger for Medical device Application using 5S LiFePo4 Battery Pack? or any Alternative suggestion please

Narendra BV
Prodigy 30 points
Part Number: BQ25730
Other Parts Discussed in Thread: PMP22419, BQ25750,

Hello, 

We are working on development of Medical device.

Fundamentally, we would like to use the Ti part BQ25730 for our application which is described below.

Please help me with the suitable answers for the questions below.

Questions are 1)  SInce  is its nowhere mentioned,  will this part works for  LiFePo4 chemistry as well?

                        2) What is the VSYS Min in this case for 19V DC adaptor input ?

                        3) WIll this work for seamless Run time switching between DC adaptor and Battery to keep the System running with 12V Supply rail?

                        4) Can we set the charge current limit to 5A initially and change later on based on the Power budget? or dynamically ?

                        5) Can i use PMP22419 reference EVM design to build the custom schematics since there is no dedicated EVM design files available for BQ25730  ?

                        6) Can you please share the design calculator file which will be normally available in XLS format.?

                        7) Is there any possibility to understand the thermal aspects for this design (I men sulilation)

Thanks in Advance.

Looking for the quick response.

Thanks 

Narendra

  • 0
    TI__Mastermind 33635 points

    Hi, Narendra,

    1. BQ25730 is a multi chemistry charger. It works with LiFePO4.

    2. VSYSMin is adjustable up to 23V.

    3-5. YES to all.

    6. design tool is online.

    7. For thermal, the easy way is to order an EVM. 

    Regards

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 30 points

    Dear Tiger, 

    Thanks a lot for your reply. Much obliged.

    Few more questions..

    1, Please advice among  BQ25730 and  BQ25750 which is most suitable for Medical applications where safety is more fundamental. 

      (BQ25750 come with built in charge profiles and Battery Temperature interface to meet certain safety aspects where as  BQ25730 is missing with these)

    2. Since we do not need the Boost topology for our implementation, Can we omit the Boost MOSFETs? 

    3. Anything special setting to be incorporated like charge Profiles for LiFePO4? or simply setting the VBat max voltage would suffice? 

    3. Please share the link for the design tool where i can  derive the right parameters and parts.

    Thanks with best Regards

    Narendra BV

  • 0 in reply to Narendra BV
    TI__Mastermind 33635 points

    Thanks for your patience. We will get back to you this week. 

  • 0 in reply to Tiger Zhou
    TI__Mastermind 33635 points

    Hi, Narendra,

    1. Both are similar performance, have been used in the medical applications previously. 

    2. Not really, there needs to have a boost FETs in the buck-boost chargers. 

    3. Both parts are multi-chemistry chargers, simply set charge voltage and charge current, they will charge.

    For a new design, it is strongly suggested to follow our BQ257XXEVM design as a starting point. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 30 points

    Dear Tiger, 

    Thanks a lot, Much obliged, This resolves my question, 

    We have ordered an BQ25730EVM for further evaluation.

    Kindly help me with Online calculation sheet if any for our custom board design .

    Will you also do schematics review ? or should i open another thread for Design review ?

    Best Regards

    Narendra BV

  • 0 in reply to Tiger Zhou
    Prodigy 30 points

    Dear Tiger, 

    In the meanwhile we are getting the BQ25730 EVM for validation,  I have one concern to clarify with you.

    with the CELL_BATPRESZ Pin setting we can set the configuration as  5S Li-ION  which sets the charging voltage as 21V  default, 

    Now the questions are 

    1. How this can be configured for LiFEPO4 by default where the maximum charging voltage is 18V ? 

    2. Since the controller is not yet ready to write the values through I2C, and my battery is connected will it not damage my battery pack ?

     As described in  8.4.1.2 Battery Charging
    The BQ25730 charges 1- to 5-cell battery in constant current (CC), and constant voltage (CV) mode. Based on
    CELL_BATPREZ pin setting, the charger sets default battery voltage 4.2 V/cell to Charge Voltage().

    3. After power on Charge Voltage Register (I2C address = 05/04h) will be reset based on CELL_BATPRESZ pin that means every POR do we have to configure the Charge Voltage Register05/04h ?

    4, Is there any possibility to hard set the Charge voltage and Charge current ? 

    5. Can you please help me to review the Power portion schematics for me? If yes please let me know how to send a copy ?

    Thanks with best Regards

    Narendra BV

  • 0 in reply to Narendra BV
    TI__Mastermind 33635 points

    Hi, Narendra,

    You can set to 4S by default then adjust the charge voltage register higher. You can treat the registers as "RAM", every time after POR, you need to set the registers again. 

    We kindly ask the customer to review their schematic by following our schematic checklist here. 

    /cfs-file/__key/communityserver-discussions-components-files/196/6170.BQ2570X_5F00_BQ2571X_5F00_BQ2572X_5F00_BQ2573X_5F00_SchematicChecklist-Rev.-A.pdf

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 30 points

    Hello Tiger, 

    Thanks for the response, we shall review the design with the checklist.

    With best Regards

    Narendra BV