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BQ25895: Quick charge IC select

user5323366
Prodigy 50 points
Part Number: BQ25895

Hello ,

Now I want to make a portable  wifi range extender，which carrying a 2000mAh single-cell lithium battery. In the extender the WiFi circuit work with 5V voltage（2A max）which is supplied by the battery.

The extender has only one type-c interface and needs to handshake the standard PD 3.0 protocol with the power adapter to realize quick charge for the battery. When the battery is charging the WiFi circuit shall be working at the same time. which means when the adapter is push in or pull out， the extender can not be powered off.

would you recommend an quick charge IC for my design, two-way fast charge is not necessary， just need to make the battery boost to  5V for the WiFi circuit?

ICs that do not require microcontroller control，the type-c interface just for power charge，no data transfer.

thanks very much！

  • 0
    TI__Guru**** 166176 points
    Unfortunately, we do not have a single chip solution for this application. I recommend a type-c interface chip, a battery charger like bq25895 and a boost converter to provide 5V, both while charging and not charging. The bq25895 charges the battery up to 4.2V and provides SYS output only up to 4.2V +50mV typical. It can boost back to its PMID pin up to 5V only when input power is not applied.
  • 0 in reply to Jeff F
    Prodigy 50 points

    Thanks, Jeff。

    2 questions:

    1、since the battery is only 2000mAh，I use an type-c interface to connect with the quick charge adapter，is an quick charge IC necessary？it will cost much more，right？

    If I use an 5V/2A normal charge IC，how long will it cost to charge up to 60%? about 30 minutes ? 90 mintutes for full?

    If I use the bq25895, the time will be ? do you have a Calculation formula，could you teach me，thanks！！

    2、inorder to charge and WiFi work at the same time，just connect the battery's +/- electrode to the boost IC to get 5 voltage，can it be OK？Do not consider the battery life.

  • 0 in reply to user5323366
    TI__Guru**** 166176 points

    Regarding 1, a 2AHr battery charging at 2A will take at least 2AHr/2A = 1Hr to charge.  Charge time is actually longer due to CV mode taper created from resistance from BAT pin to battery and the battery's own impedance as well as the termination current setting.  I use 2AHr/2A*1.5 = 1.5A as a rule of thumb.  Quick charge adapter providing >5A is not really helpful when you only need 2A charge current.

    Regarding 2, I recommend connecting SYS to the boost converter input instead of battery.  When power is applied at VBUS, the charger provides the SYS_MIN voltage at SYS, which will be less taxing on the boost IC to provide 5V.