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BQ2416x Questions

lava
Prodigy 100 points

A few questions about the BQ2416x chip. Here we go:

- Showing my ignorance here; regarding USB detection I don't know whether I should choose a part with D+/D- or PSEL. I want to use a dumb micro USB charger to charge a battery via a BQ2416x IC. Neither of the descriptions for these pins in the datasheet make sense to me.

- Similarly, where do I plug that USB charger in? At the IN pin or the USB pin? I assume the USB pin, but in the application schematic on page 4 of the datasheet, it shows "AC Adapter or Wireless Power" plugged into the IN pin. A wall plug micro USB charger is in fact an AC (to DC) adapter. Which is it?

- Regarding the application schematic; can the Host be part of the System Load? I.e., is the default state of the BQ to allow power through to the System Load so that the host can start up and commence battery charging?

Thanks!

  • 0
    TI__Guru**** 166156 points
    16x D+/D- pins communicate with USB port D+/D- to determine whether the port is SDP and therefore only capable of 100mA or DCP and therefore capable of 1.5A. The USB port connects to USB input and D+/D- lines. The host can be part of the system but if SDP port is connected, input current is limited to 100mA. Can your system start up with 100mA, enumerate USB and then reset input current limit as allowed per enumeration?
  • 0 in reply to Jeff F
    Prodigy 100 points
    Yes, my system can start up with 100mA, no problem.

    So you're saying that choosing the BQ version with D+/D- would allow me to charge from either a USB wall charger OR from a USB socket on a laptop? Would the PSEL version not allow that? In what type of case would I want the PSEL version?

    Thanks!
  • 0 in reply to lava
    TI__Guru**** 166156 points
    Yes. Later chargers (although none with dual input) have more advanced D+/D- detection that can detect SDP, CDP or DCP. PSEL lets you set the input current to either 100mA or 1500mA based on the logic level of the PSEL pin. If you had a USB PHY chip connected to D+/D-, the output of that chip could control PSEL.
  • 0 in reply to Jeff F
    Prodigy 100 points
    Thanks very much for all your help!
  • 0 in reply to lava
    Prodigy 100 points

    Another question:

    With regard to the INT pin, the datasheet states "Connect INT to a logic rail through a 100kΩ resistor to communicate with the host processor". This statement implies that I must have a 100k Ohm resistor in series between the INT pin and a GPIO pin on a host processor. But in all of the application diagrams, the INT pin is shown connected directly to the host processor with no resistor in series. There is a pull up resistor shown, but 100k would seem to be slightly large a value for a pullup.

    So which is it? A series resistor or pullup resistor? And why 100k?

  • 0 in reply to lava
    TI__Guru**** 166156 points

    INT is open drain.  The resistor needs to be a pull up resistor to a voltage not to exceed 6V.  The INT pin is used during manufacturing for testing and has some circuitry cannot withstand higher currents.  The abs maximum current through into INT should be less than 1mA.