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BQ25713: 5v ups

Pritesh Metha
Prodigy 190 points
Part Number: BQ25713

Hi,

I am designing raspberry pi 3B UPS HAT. For that we have 4.5V to 5V input power supply and we want to charge 18650 li ion battery(4.2V) at same time we want 5V system output even for 4.5V adapter input voltage. In case of input adapter power failure we need 5V system voltage(offline mode).Will this BQ25713 suitable for this requirement.   

  • 0
    TI__Mastermind 24075 points

    Hi Pritesh,

       A couple of points to keep in mind:

    • When your adapter is present, you can have the VSYSMIN regulated to 5V (converter will operate in boost to supply SYS), however as battery voltage is < VSYSMIN, the part will be operating in LDO mode
      • In LDO mode, charge current is clamped and regulated to 384mA when EN_LDO
      • When EN_LDO is removed, the charge current is not regulated and set by the battery pack internal resistance
    When adapter is removed and battery is present, VSYS will track VBAT
    • There is only the FET controlled by BATDRV between BAT and SYS (adapter not present) so there is no way to boost the battery voltage to maintain an uninterrupted 5V VSYS rail even when adapter is missing.

    I would recommend also having a boost converter at SYS to

    1. Avoid always having to be in LDO mode
    2. Maintain 5V VSYS when adapter absent and only battery present.

  • 0 in reply to Kedar Manishankar
    Prodigy 190 points

    Hi Kedar ,

    Please suggest what should be the VSYS voltage for better operation if input adapter voltage is between 3.5V to 24V.battery is 1S 4.2V li ion 18650 cell and also suggest boost converter to get 5V and up to 4A continuous current.

  • 0 in reply to Pritesh Metha
    TI__Mastermind 24075 points

    Hi Pritesh,

       Setting VSYSMIN depends on your system, and if you have a boost converter connected or not. For 1S battery, the precharge to fast charge threshold is 3V, and part will operate in LDO mode until VBAT exceeds VSYSMIN setting. Generally 3.5V VSYSMIN is popular.

    You can take a look at our boost converter portfolio here: www.ti.com/.../overview.html