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Inquiries regarding charge current detection on BQ27520-G4

Atsushi Okui
Genius 4015 points
Other Parts Discussed in Thread: BQ27520-G4, BQ26500, BQ27510-G1, BQ27500, BQ27742-G1, BQ27545-G1, BQ27510

Hello, all

Now we have one inquiries regarding charge current detection on BQ27520-G4 from our customer.

Please refer to the item below, and feedback us with your comment.

1) On previous model which used bq26500, we used the fuctionality of CHGS on Flags to identify charge current.

However, we could not find out similar register on BQ27520-G4.

We would like to implement charge stop function into the MCU, in case that the charge current is increased despite that the supervisor detects that the charge has been already done.

Please let us clarify how we could identify charge current on this. 

2) When referring "FUNCTIONAL DESCRIPTION" on page 20 of bq27510-G1 (SLUS927), the following description was found.

When RemainingCapacity( ) falls below the second capacity threshold, SOCF Set Threshold, the [SOCF] (State of Charge Final) flag is set, serving as a final discharge warning.

Meanwhile, when referring "FUNCTIONAL DESCRIPTION" on page 11 of bq27520-G4 (SLUSB20A), the following description was found. 

As Voltage( ) falls below the SysDown Set Volt Threshold, the Flags( ) [SYSDOWN] bit is set and SOC_INT will toggle once to provide a final warning to shut down the system.

Please let us clarify why the algorithm itself was changed between these devices.

We thank you in advance for your information.

Best regards,

  • 0
    TI__Guru* 76230 points

    Hi Atsushi,

    1. The chg bit still exists in thebq27520 in the flag register.

    2. These are two different devices and our algorithms are usually modified in newer generation of devices based on gathered feedback from customers and tests which has been carried out

     

    thanks

    Onyx.

  • 0 in reply to Onyx Ahiakwo
    Genius 4015 points

    Onyx-san,

    Thank you for your prompt reply on the inquiries regarding bq27520-G4 from our customer.

    With regard to your answer (1), when referring "Table 2-5. Flags Bit Definitions" on page 12 of Technical Reference Manual (SLUUA35), we understand that CHG (bit 0) is just indicating OK to charge.

    For our customer's case, they are willing to identify charge current. Therefore, it is difficult for them to use this register for this purpose.

    If CHG (bit 0) is corresponded with CHGS on bq26500, please let us clarify how we could use this register.

    We thank you once again for your information.

    Best regards, 

  • 0 in reply to Atsushi Okui
    TI__Guru* 76230 points

    Hi Atsushi,

    I didn't realise you were refering to the bq26500. I misread and thought you were talking about the bq27500 of the which the chg bit in the bq275x family are similar.

    The bq26500 was the original bqJunior gauge which uses an EDV algorithm and primarily relies on coulomb counting.  The CHG bit was used to indicate charging current was present.  Also, bqJunior gauges are generally used inside of battery packs and not on the main system board unless the battery is non-removable.  

     The bq27520-G4 is is much newer and uses the Impedance Track algorithm. It is generally used on the system-side and not placed in the battery pack.   Our gauges like bq27545-G1 or bq27742-G1 are the IT gauges which would be used inside a battery pack.   The CHG bit in these IT gauges has a different function than the bqJunior family.   The CHG bit means "ok to charge".  To determine if charging is occurring you need to look for positive current in the AverageCurrent( ) register.   

    My apologies for the initial confusion.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 230 points
    Dear Onyx-san,

    I am Nobuhiro Haruta of KTL Japan.
    Okui-san left the office, and I succeeded his work.

    I received a new question from customer.

    I show customer question and Okui-san answer as follows first.

    *Customer question
    Q1：What is the meaning of CHG?
    　　And would you please inform a meaning of CHG and a set condition of CHG?
    (A1): The CHG bit means "ok to charge".
    CHG = Indicates OK to charge.
    This bit is set if StateOfCharge( ) is below TCA Set % and Temperature( ) is within
    the ranges set by Chg Inhibit Temp Low/High and Suspend Low/High Temp.
    This bit is cleared when StateOfCharge( ) rises above TCA Clear %, unless TCA Clear % is set to –1.
    If TCA Clear % = –1, then this bit is cleared when primary charge termination is detected.
    If FC Set % = –1, then the CHG bit clears at the same moment as the FC bit is set when
    primary charge termination is detected.

    Reference document：
    www.ti.com/.../sluua35.pdf

    Q2：About connected battery, would you please inform the judgment method that battery is charged?
    Q3：Customer judged a charge state in CHGS　by BQ26500.
    　　 About CHGS equal function, do you have BQ27510 and BQ27520?
    (A2)、(A3):
    To determine if charging is occurring you need to look for positive current in the AverageCurrent( ) register.

    Q4：Flags:SOFC of BQ27510 is changed to Flag:SYSDOWN in BQ27520.
    　　 Is there any intention?
    (A4): These are two different devices and our algorithms are usually modified in newer generation
    of devices based on gathered feedback from customers and tests which has been carried out.


    New question from customer.
    Please refer to follows.
    ----------------------------------------------------------------------------------------------------------------------------------
    *New question
    ① Do you have Flags:CHGS equivalency Flag of BQ26500 in BQ27510 and BQ27520?

    ②About first Q1, in TCA clear and TCA set, datasheet does not have a mention.
    　 Which mention of datasheet do TCA clear and TCA set correspond to?

    ③About first Q1,
    Customer understood that explanation contents of datasheet 24page(Detecting Charge Termination)
    of BQ27510 and the contents of the Q1 answer were not correct.
    By contents along datasheet(24page) of BQ27510, would you explain Q1 again?
    ---------------------------------------------------------------------------------------------------------------------------------

    Best regards.

    Haruta
  • 0 in reply to Nobuhiro Haruta
    TI__Guru* 76230 points
    1. No we do not have an equivalent flag.
    2. the TCA set and clear are SOC thresholds which you set in the data flash. The y are properly defined and explained in the technical reference manual (TRM).Pls point your customer to that.
    3. The definition of the chg bit as explained in the TRM is correct for the bq275xx
    thanksOnyx