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BQ24773: Design Changes with BQ24773

Kavitha Ajay
Prodigy 60 points
Part Number: BQ24773
Other Parts Discussed in Thread: BQ24780, , BQ24780S

Hi,

Due to some reasons the charger IC design changing from BQ24780 to BQ24773,

wanted to know what and all the design considerations to be taken care for NVDC ex. does NVDC takes more thermal dissipation needs than Hybrid,. as it is a dense board designed with BQ24780

How the switching and its functionality of SRN/SRP pins differs as the SRP goes to Vsys

is NVDC good pick for Dense board charger design with other communication protocols sections also in it,. requirement is, 2S2P charging and delivering 1A in general, and +1A  peak power for some time.

let me know your inputs.

  • +1
    TI__Mastermind 24075 points

    Hi Kavitha,

       Yes, the NVDC architecture can help supplement SYS load for portions of time when it exceeds adapter supply capabilities. The SRP/SRN pins will still be used similarly as in BQ24780s. This is because even in BQ24773 the SRP/SRN differential voltage is to sense charge current only (not ISYS + IBAT). And the SRN is used to detect battery voltage, so even though SRP is at VSYS there is no issue.

    With regards to thermal dissipation for BQ24773, when BATFET is in linear mode (VBAT < VSYSMIN) there will be some extra thermal dissipation as opposed to when VBAT > VSYSMIN. Apart from that as your system considerations are not changing there should be no issues. Both charger layouts should already be designed for optimal thermal dissipation using a clean ground plane. As they are both 28pin QFN devices, use sufficient vias from the ground pad of the QFN IC to an internal or external ground layer to dissipate the heat. They have the same package so switching to this part really shouldn't affect the layout as it should already have been implemented.