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BQ24295 OTG Boost mode operation

Kuo Duke
Expert 2040 points
Other Parts Discussed in Thread: BQ24295

Hi all,

project information

Input  : AC 8 ~ 24VAC

Output : 5 V / 1A

even 1 : when system load > 3W, battery with AC provide power

even 2 : when system load < 3W, only AC provide power

So I evaluating Wide Vin DC/DC with BQ24295 now, but have some question need to let me know,

OTG - boost mode can use only Standalone methodology ?

ILIMI -  can use only Standalone methodology ?

  • 0
    TI__Genius 13700 points
    Hello,

    You are supplying AC voltage to the bq24295?

    First,this part requires DC voltage and the max voltage that it will support on VBUS while enabling charging is 6VDC.
    With that in mind your input voltage of 8VAC - 24VAC will destroy this part and even if the AC wave form existed between 0V and 6VDC it would not pass this voltage through to your system.

    Regarding your questions.
    OTG question:

    If you look at the OTG pin description in the datasheet in page 4 and at the OTG section of the datasheet 8.3.1.3 it will be clear. When the OTG pin of the device is pulled high and bit 5 of REG01 (Section 8.6.1.2) is set to 1 which it is by default it will be in OTG. That being said if you have the OTG pin pulled high and there is not voltage on VBUS from another source by default the device will boost back OTG.

    ILIM Question:

    The ILIM can be set by an external resistor connected to the ILIM pin. It can also be set by a register. Between the two methods of setting the ILIM the device will select the lower limit. The integrated ILIM is different depending on the what sort of port the device is connected to which is determines by the D+/D- lines.
    All that being said you can set the ILIM in standalone mode. Use the Klim factor of 435 as discussed in the datasheet electrical table on page 7 with equation 3 of section 8.3.5.1 so solve for the Rlim value needed for the ILIM you want to set.