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BQ25155: About what does mean "IC2 disabled exactly" when Low Power Mode.

Koki Tsushima
Prodigy 695 points
Part Number: BQ25155

Dear expert.

I am Koki and I want to ask about what does means "IC2 disabled exactly" when Low Power Mode. 

In other words, what will be operated?

According to the datasheet on page 34 , which is 

"During LP mode the VDD output is powered by BAT, the MR inputs are active and the I 2C and ADC are disabled.",

I2C is invalid on this low power mode.

Does this mean that are there nothing which could be acceptable as an I2C interface?  

Is this like reset signal? What I mean is are there are no possibilities to holding missed data because I2C may not be stable?

I am asking this because my customer wants to use this devices just after power on.

For that time, I2C signal could be flapping.

　 

Best regards,

Koki Tsushima

  • 0
    TI__Expert 4205 points

    Hi Koki, 

    While operating from battery only, the LP pin will control if the device is on low power mode or active battery mode. The pin is internally pull low with a 900k ( in low power mode), while on low power mode the I2C  communication will NACK. If you want to perform I2C communication while operating from battery only, you'll need to drive it high (like with a MCU control pin) to allow the I2C communication. 

    You should be able to communicate via I2C just after power-on without any problems, just need to make sure the LP is driven high while on BAT only, or that VIN is present. 

    Best Regards, 

    Arelis G. Guerrero 

  • 0 in reply to Arelis Guerrero
    TI__Prodigy 695 points

    Hi Arelis-san,

    I understood that the I2C communicate will NACK and be able to communicate via I2C just after power-on.

    How about when it was activated by Vin, VBATT? 

  • 0 in reply to Koki Tsushima
    TI__Expert 4205 points

    Hi Koki-san, 

    If VIN is present, the I2C communication will be active. You are going to be able to communicate via I2C with the device at all times, regardless of VBAT value or the LP state. 

    If VIN is not present, and only VBAT is present and VBAT is above BATUVLO. Then, you are only going to be able to communicate via I2C with the device, if the LP pin (Pin No. D3 on package) is driven high by the MCU (active battery mode). If the LP pin is low, then device will be on low power mode, and you will not be able to talk to the part on I2C. 

    Best regards, 

    Arelis G. Guerrero 

  • 0 in reply to Arelis Guerrero
    TI__Prodigy 695 points

    Hi Arelis-san,

    I understood that LP mode is valid only for when VBAT is activated, not by Vin is activated.

    And when LP is activated, I2C communicate will NACK and be able to communicate via I2C just after power-on.

    Are they correct?

    Best regards,

    Koki Tsushima

  • +1 in reply to Koki Tsushima
    TI__Expert 4205 points

    Hi Koki-san, 

    "I understood that LP mode is valid only for when VBAT is activated, not by Vin is activated." - correct

    "And when LP is activated, I2C communicate will NACK and be able to communicate via I2C just after power-on." -No, during LP mode the I2C communication will not work (NACK). 

    The below true table shows the I2C communication based on VIN, VBAT and LP states. 

    VIN Valid? VBAT Valid? LP Pin I2C Communication
    YES YES HIGH YES
    YES NO HIGH YES
    YES YES LOW YES
    YES NO LOW YES
    NO YES HIGH YES - Active Battery Mode
    NO NO HIGH NO
    NO YES LOW NO - Low Power Mode
    NO NO LOW NO

    Best regards, 

    Arelis G. Guerrero