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BQ24295 charger : AC adapter detection

Hank Chu
Expert 1340 points
Other Parts Discussed in Thread: BQ24295

We used TI BQ24295 charger in the product.

 

1) And the product used an AC adapter for battery charging.

1-1) The USB D+/D- pins of AC adapter are shorted and connected to GROUND.

2) In the datasheet of BQ24295, Chapter 8.3.1.4.4, it said:

2-1) when the charging source passes data contact detect, the device would proceed

        to run primary detection.

      Otherwise the charger would proceed to run non-standard adapter detection.

 

Q-1) Will BQ24295 do the primary detection for the AC adapter (D+/D- shorted and connected to GROUND) of IG1?

Q-2) Is the AC adapter (D+/D- shorted and connected to GROUND) of IG1 supported by

the non-standard adapter detection of BQ24295?


 

3) About the BQ24295 Non-Standard Adapter Detection, please refer to the picture below.


4) About the power circuit of BQ24295, please refer to the picture below.

Thank you.

 

  • 0
    TI__Mastermind 25800 points

    Hey Hank, 

    Q-1) If I understood your setup correctly, because you have the D+ and D- pins tied together AND tied to ground, the bq24295 will do Primery Detection.

    Q-2) Because the charger will run Primary Detection on your adapter is stated above, it will not look like a Non-Standard adapter to the charger. In fact, it will most likely look like a SDP to the 24295 based on the configuration you described.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Expert 1340 points

    Thank you for your kind support.

    1) In the Battery Charging Specification 1.2 (December 7, 2010), 

    1-1) In the Chapter 3.2.3.1, it describes the DCD (Data Contact Detect) as follows:

    >>  A PD is not required to implement DCD.

    1-2) In the Chapter 3.2.4, it describes the Primary Detection as follows:

    >> A PD is required to implement Primary Detection.

    1-3)  a DCP (Dedicated Charging Port) is required to short D+ to D- through a resistance of RDCP_DAT,
    and the PD will detect a voltage on D- the is close to VDP_SRC.

        About the details, please refer to the picture below.

    1-3-1) The RDCP_DAT is maximum 200 ohm in BC1.2 specification.

    2) The USB D+/D- pins of AC adapter (for our product) are shorted and connected to GROUND.

    2-1) And this AC adapter does not have the RDCP_DAT resistor.

    Q-3) Are the following detection procedures of this AC adapter with BQ24295 correct?

    3-1) The detection of DCD with BQ24295 failed because the USB D+/D- pins of this AC adapter are shorted.

    3-2) And then, BQ24295 did the Primary Detection (Not detection of Non-Standard Adapter)

    3-2-1) The Primary Detection of DCP failed because this AC adapter does not have the RDCP_DAT resistor.

    3-2-2) So, the BQ24295 detected this AC adapter as USB host (SDP).

    Thank you.

  • 0 in reply to Hank Chu
    TI__Mastermind 25800 points

    Hey Hank,

    So this is the procedure that will happen on our charger because the D+ and D- are Shorted AND Grounded.

    1) The adapter will PASS detection of DCD because the voltage @ D+ will be below a certain threshold.

    2) From DCD detection, it will perform Primary Detection (PD). Because the D- voltage is also below a certain threshold, our charger will identify your adapter as a SDP.

    So it failed DCP detection because you have D- connected to ground, not because they are shorted. 

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Expert 1340 points
    Thank you for your kind support.
    We understand the procedures of detection by the charger now.

    Please do us a favor to close this case.