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BQ24195: PMID and VBUS problem for BQ24195

user4463182
Prodigy 20 points
Part Number: BQ24195

Hello,

 We use BQ24195 for our product, but i cannot understand the relationship between VBUS and PMID pins on BQ24195.

Based on the datasheet. 

1, PMID can be used for power bank mode which will generate 5.1V if using battery.

2, There is a diode between PMID and VBUS, which means the current can go through VBUS to PMID.

3. So if the voltage on VBUS is bigger than 5V then, is there a change to damage a device that attached to PMID for charging.

4. Or it's a design rule that the VBUS shouldn't higher than 5V when using PMID for charge a device which can only bear 5V maximum?

Hope anyone can clear my questions,

thanks in advance.

  • 0
    TI__Expert 8230 points

    Hello,

    When using the bq24195 for powerbank applications, there are couple things to note:

    • OTG mode and battery charging cannot be enabled at the same time. When OTG mode is enabled to provide the 5V output on PMID, the converter operates in boost mode. 
    • If VBUS greater than BAT+VSLEEP, OTG is disabled.
    • In addition, there is additional circuitry on VBUS to pull the OTG pin low whenever VBUS is applied. 

    You did bring up a good point which is, if a peripheral is connected at PMID, it must withstand the entire operating range of VBUS expected for that application. If the user connects the wrong adapter, let's say 9V, PMID will see 9V. Preventive measures must be taken to ensure the peripheral connected on PMID only sees the correct voltage, for example, adding extra circuitry at PMID to clamp the voltage.

    Hope this helps.

  • 0 in reply to Fernando Lopez
    Prodigy 20 points

    Hey Fernando,

    thanks for your explanation, that's quite clear to me know. I will design the circuit based on your suggestions