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BQ24297: Use of shipping mode without chargers & use of OTG pin

Stefano Infante
Expert 2320 points
Part Number: BQ24297

Hello,

I have a couple of questions about BQ24297:

1) Table 2 on the data sheet states that OTG is used for selecting between 100 mA and 500 mA when a USB host is connected, but is the OTG pin only used for USB on-the-go mode? As I don't need this mode, can I ignore that pin and tie it to VDD or GND?

2) I find shipping mode to be a very interesting feature, but it is not clear to me whether it can be used when battery is the only power source in the system. I would like to use the available ON/OFF button to go into and exit shipping mode, but the data sheet in section 9.3.1.2.2 states that "system voltage is zero". Does this mean there would be no way to "awake" the system without an external power source?

Thanks in advance.


Regards,

Stefano

  • 0
    TI__Expert 8230 points
    Hello Stefano,

    Regarding question#1, the bq24297 includes D+/D- detection for USB hosts. The OTG pin plays a part in USB detection when the adapter plugs in. If the 297 detects an SDP host, in order to differentiate between SPD100 or SDP500, the state of the OTG pin is used where OTG=LOW corresponds to an input current limit of 100mA and OTG=HIGH to an input current limit of 500mA. Please note this is to set the input current limit as a result of an adapter plug in. The input current limit can be modified by the host via I2C after the adapter is plugged in.

    If you don't intend on using OTG in your application, you can fix the state of the pin to either high or low depending on the input current limit you want to when and if a USB host is connected.

    Regarding question#2, SHIP mode is used to place the device in a low power state before leaving the assembly line. Typically, it is not used an as on/off button for the system during regular operation. Once ship mode is enabled, the internal BATFET between BAT and SYS is turned off preventing charge and discharge of the battery; this is why the SYS will be 0V and the only way to exit this is by plugging in the adapter.

    If you need to place the device in a low power state during operation, your host can place the device in HIZ.