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BQ24195: Understanding of Overview

Adam Wheeler
Intellectual 270 points
Other Parts Discussed in Thread: BQ24195, BQ24030, BQ24190, BQ24192

Hi everyone,

I am looking at the BQ24195 as my PMIC for a little project I have going on. The basic requirements are that I will have a 5V/3A input that needs to supply a load and charge a LiPo battery simultaneously, as well as support the load in the case of a loss of input power (i.e be able to provide 5V/3A if the input supply is unplugged). TI's PowerPath seems to be exactly what I need, but I have a few questions regarding this part:

When the input power is supplied, will the output on the SYS pins just be Vin/Iin?

If PMID is the boosted voltage from the battery (3.7V from the LiPo to ~5.2V output), would this not just be connected to the same output lines at SYS to support the system load? In the example diagram in the datasheet, PMID is connected to a phone/tablet, and SYS is supporting some other load.

This part seems more complicated in conceptual understand to me than the BQ24030, for example. Any help in the higher level breakdown of the chip's functionality would be appreciated, as I've been looking through this datasheet reading the same things over and over for a little while now.

Thanks,

-Adam

  • 0
    TI__Expert 8230 points

    Hello Adam,

    The bq24195 is tailored for powerbank applications; the output of the boost converter is through the PMID pin instead of the VBUS pin on the other devices part of the 19x family. Please note that this device cannot boost and charge at the same time.

    When the adapter is connected, its power will be split between the system load and charging the battery. In a typical application, you would have your system load connected to the SYS pin, your battery to the BAT pin and your adapter would provide power to the system while charging the battery, assuming the adapter can provide the required power. If your adapter provides 15W (5V/3A), that means your charging needs+your system power consumption must be less than 15W minus the efficiency drop of the buck converter.

    If your system consumes more than 15W, and the adapter current limit is being reached, the device will start decreasing the charge current to ensure the system doesn't crash. If the system's power consumption keeps increasing, the device will enter supplement mode and start discharging the battery to provide power to the system. When the adapter is connected, the SYS pin is regulated between MINSYS (typically 3.5V but can be changed via I2C) and the battery voltage + ~150mV.

    For example, with an adapter connected, if your battery voltage is 3V, SYS will be regulated to MINSYS or 3.5V. Once the battery voltage increases past MINSYS, the SYS pin will follow the battery voltage +150mV.

    I recommend you also review the bq24192 or bq24190 and see how the system is connected in this application.

    Hope this helps.

  • 0 in reply to Fernando Lopez
    Intellectual 270 points

    Hi Fernando,

    Thank you for your reply; this does help in my application understanding. Given what you said, it seems that the BQ2403X series is more along the lines of what I am looking for with its Dynamic Power-Path Management feature enabling it to supply the load and charge my LiPo battery simultaneously. The power flow diagram is much more in line with what I need as well, as I can always take the output of the BQ2403X and use it an the input to a Boost chip to supply my system load.

    Thanks again for your help!

    -Adam

  • 0 in reply to Adam Wheeler
    TI__Expert 8230 points
    Hello Adam,

    Just wanted to clarify, the bq2419x family of chargers also provide dynamic power-path management, so you can achieve the same using the 19x family. You connect a boost converter to the SYS pin that operates within the MINSYS-Max charging voltage of your Li-po battery and power your system. Please also note that the bq2403X are linear chargers while the 19x are switching chargers, so please consider your current needs (charging and system currents) as well to ensure your efficiency is adequate for your application. Just wanted to add a bit more information. :)