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BQ24192: Pin configuration and set up questions for a new build.

Jez
Prodigy 10 points
Part Number: BQ24192
Other Parts Discussed in Thread: TPD4S014

Hello. 

I have been tasked with setting up a new battery charging system using the BQ24192. I have some questions regarding the setup of some of the pins that wasn't clear to me in the data sheet. 

My work has used this chip in the past and I was given an old schematic to work form. The people that made the schematic are no long with the company though. 

My questions are the following.

OTG: For the project we want to be able to charge form a USB port at 500mA or from a 5v DC adapter for 3A charging. I have set up some switching so only one can feed the system at a time. To make this happen my understanding is, when OTG and PSEL are both pulled HIGH this puts the charger into 500mA USB mode, and when PSEL is LOW this will put it in DC adapter mode. My question is, if OTG is always HIGH but PSEL is switched from LOW to HIGH will it still change modes? Or does OTG need to be switched as well? 

Also, I’ve been doing some reading on USB port power negotiation and I’m not sure if putting the BQ24192 into OTG mode is enough to get 500mA from a USB port. Right now, all I have on my USB input is a TPD4S014 USB Charger Port Protection. Will putting the BQ24192 in OTG mode mean it can draw 500mA from any USB port?

TS1 and TS2: We only want to use one battery in the system. So, what is the best thing to do with TS2 if it not going to be used? Should it be joined to TS1? or not connected at all?

CE: In the old schematic I was given this pin was left unconnected and the charger worked. But in the data sheet it says it must be pulled LOW to enable charging? What should be done with this pin? I don't fully understand what this is used for. 

In lay Layout Guidelines is says "Route analog ground separately from power ground". In the schematic I was given this wasn't done but again it worked. I'd like to separate them but i'm new and don't want to brake a design that 'worked'. Are there some special situations where this doesn't have to be done? I'm guessing its done to reduce or control noise on the ground circuits? 

Thank you for your time. 

Jez 

  • 0
    TI__Intellectual 1410 points
    Hi Jez,

    Thanks for using BQ24192 in your new design. I also recommend looking at the BQ2419x evaluation module for additional schematic help as well as an example layout. For your questions:

    OTG and PSEL: To change the adapter current limit you will need some I2C integration. REG07, Bit 7 will force the D+/D- detection that will set the input current limit when switching from one adapter to another. For the pins, I would set them for the more typically used input source.

    OTG mode is using the converter in boost mode from battery. Section 9.3.1.5 of the BQ24192 datasheet (page 16) has a good description of that mode.

    TS1 and TS2L: If you are only using one battery these pins should be shorted together.

    CE: Enabling charging can be done by either hardware or software. By hardware this is done by pulling the CE pin low. In I2C that is controlled with REG01, Bits 5 and 4. [5 4], 00 = Charge Disable, 01 = Charge Enable.

    Layout: Separate analog and power ground returns are used for noise considerations so it will depend on the rest of the system that shares the same ground.

    Thanks,
    John