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BQ27220: Schematic Review : Battery Charger + Fuel Gauge

Dev
Prodigy 140 points
Part Number: BQ27220
Other Parts Discussed in Thread: BQ24610, , EV2400, BQ25606, BQSTUDIO, GPCCEDV, BQ27320, BQ24610EVM

Dear TI team,

I am currently working on a project that needs a Battery Charger and a Fuel Gauge for accurate Battery SoC tracking.
For the Charger I have chosen, BQ24610 and for the fuel gauge, I have chosen BQ27220.

Following are the Input and Output specs of the system,

Input: DC charger with 5V, 5A capabilities.

Battery Specs: 1S2P, 3.6V Nominal Voltage(4.2V Max), Li-Ion Pack(10,000mAh). The battery charge current needed is 4.5A.

I have made the following attached schematic based on reading the datasheets of both ICs. Can someone from both the charger and fuel gauge teams confirm if the schematic is OK before I proceed to the PCB layout section?

I also had the following questions while designing.

  1. For BQ27220, what is the nominal voltage for SDA SCL lines for BQ27220? Can I interface(read/write) it with a 3V3 voltage compatible microcontroller without any voltage translations?
  2. Is the position of the sense resistor for BQ27220 correctly placed in the BQ24610 charger path?
  3. Can someone explain, the use of R3 and C3 mentioned in the schematic, placed between the 2 PMOSs in BQ24610?
  4. In the fast charge mode of the battery when set at a charge current of 4.5A and the DC input limit set at 5A, Can I assume that the rest of the 500mA will be available at the output of the BQ27220(Vsys node) while the charge is in progress?

It will be great if someone can help with the above. Thanking you in advance.

6886.Schematic-Review.pdf

  • +1
    TI__Mastermind 20221 points

    Hello Dev, 

    1. The recommended pull-up voltage for the SDA and SCL lines as specified in the datasheet is between 1.62V and 3.6V. Please see the image below. 

    There should not be any issues with having the SDA and SCL lines pulled up to 3.3V. 

    2. I do not see any obvious issues with how the sense resistor is configured with respect to the fuel gauge. To determine if the sense resistor configuration is good with respect to the battery charger, I will have to leave this to the charger team. 

    3. Looping in the charger team to answer this.

    4. I am not sure if I understand what you are asking here, can you please elaborate? 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Prodigy 140 points

    Thank you for Answer 1. It's clear now.
    Is there a walkthrough guide on how to create the golden image for BQ27220? I haven't worked with TI's Fuel gauges before and just got to know about the charge cycle learning to be done. I have ordered the BQ27220EVM and EV2400. Is there any to get the unit functional without the learning cycle(Just plug and play)?

    Regarding question 4,
    What I wanted to ask was if dynamic power management was possible with the charger IC. Meaning if the input DC adapter current is 5A, and 4.5A of it goes to the battery for charging. Is the remaining current of 500mA from the DC adapter available to power the circuits connected downstream of the VSYS node mentioned in the schematic? The last TI battery charger I used was BQ25606 and it used to support this feature.

    Hoping I made my question clear. 

  • 0 in reply to Dev
    TI__Mastermind 20221 points

    Hello Dev, 

    I recommend referring to the BQ27220 EVM User's Guide. Additionally, you should use the GPCCEDV tool instead of a learning cycle since this is a CEDV gauge, the following E2E thread should be helpful here. 

    I will hand this off to the chargers team to help with the remaining questions. 

    Regards, 

    Jonny. 

  • +1 in reply to Jonny
    TI__Mastermind 20490 points

    Hello Dev,

    I don't see any obvious issues with the schematic.

    Dev said:
    Regarding question 4,
    What I wanted to ask was if dynamic power management was possible with the charger IC. Meaning if the input DC adapter current is 5A, and 4.5A of it goes to the battery for charging. Is the remaining current of 500mA from the DC adapter available to power the circuits connected downstream of the VSYS node mentioned in the schematic? The last TI battery charger I used was BQ25606 and it used to support this feature.

    Yes, However the sys load will take priority over battery charging. If the sys load requires more current the charging current will decrease.

    Best Regards,

    Christian.

  • 0 in reply to Jonny
    Prodigy 140 points

    Thanks, Jonny for the help. I will go through them and let you in case I have some issues with it.

    @Christain Moyer. Thank you for verifying the schematic section of the charger and DPM section. Can you please let me know regarding Qn 3? I don't know if the values selected are correct for R3 and C3 in the design are correct and how to choose them. I am not using an input filter as I am using a TVS diode to clamp the input in case of a input spike. 

  • 0 in reply to Dev
    TI__Mastermind 20490 points

    Hello Dev,

    Dev said:
    I don't know if the values selected are correct for R3 and C3 in the design are correct and how to choose them

    Yes these values are correct. They are used for Additional turn-on delay for Q2 to further limit dI/dt and limit inrush current.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 140 points

    Thank you.

  • 0 in reply to Jonny
    Prodigy 140 points

    I was testing yesterday with the BQ27220EVM and EV2400. The wiring was successful and I was able to read registers from BqStudio software(version 1.3.124). I can see the readings change when the battery is charged/discharged.  I cannot seem to figure out how to proceed further. There seems to be a mention of using the e GPCCEDV tool. But when I check the link it it just contains a user guide which I am not able to make sense of. Is this a different tool? Or I am to use BQStudio for learning charge-discharge curves. There seems to be something missing in my understanding of the entire flow. Can you help me answer the following? Apologies upfront if some questions look dumb. I am using TI's fuel gauges for the first time


    1. How do I go about using the GPCCEDV tool? The user guide talks about getting a zip file made. How do I go about doing that? Which tool do I use or is it a manual method to generate the zip file? Is there a step by step instructions for the same?  The document says "An easy recording method utilizes TI's bqStudio software utility called GPC Packager that reads data
    directly from a TI fuel gauge.". I seem to have no idea where to access this utility in bqstudio software.

    2. Is there even a need to do Step No. 1? Or can I proceed with setting Full charge capacity, charging voltage and a few key parameters via I2C from my microcontroller every time it turns ON and call it a day?


    3. GPCCEDV tool link says "Gauging Parameter Calculation report to be emailed to you." and "The generated report includes values for EMF, EDVC0, EDVC1, EDVR1, EDVR0, EDVT0, EDVTC, VOC75, VOC50, VOC25 (some of these values may not apply to specific gauges) and an OCV11.txt file which contains 11 point loaded voltage points which can be used on TI gauges bq27320 and bq27220." How do I use this information post the report generation? Am I to use these values and program bq27220 via i2c with these settings every time it turns ON? Or is it stored permanently in the device once it's saved the first time via I2C? How would I use the BQ27220 in production? There seem to be a lot of settings to be configured.

    Regarding the schematic shared above, I found a couple of errors when I was playing around with the EVMs. I had to change the bq27220 sense resistor position as shown below. Seems to work with the EVMs. (Just sharing if anyone looks into this in future)
    Changes


    Also, I  wrongly assigned the VDD pin of bq27220 to 3.3V which was also wrong. So I removed that too.


    During the testing of the BQ24610EVM I found that whenever the battery is fully charged or near above 4V in open battery voltage, I am not able to get it to charge with an input DC adapter input at 5V. I have to increase the input voltage to 6V or so to get it to charge if input power is lost. Can you tell me why this is so? Is there a way for me to get the 4.2V nominal cell charging with a 5V DC voltage adapter? I would really prefer if this can be made possible with a 5V adapter than a 6V adapter. Can you please let me know what can be done regarding this issue?

  • 0 in reply to Dev
    TI__Mastermind 20490 points

    Hello Dev,

    Please refer to section 11 Power Supply Recommendations in the datasheet:

    TI recommends an input voltage of at least 1.5 V to 2 V higher than the battery voltage, taking into consideration the DC losses in the high-side FET (Rdson), inductor (DCR), and input sense resistor (between ACP and ACN), the body diode drop of RBFET between VCC and input power supply, and battery sense resistor (between SRP and SRN).

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 140 points

    Thanks, Christian for the response. I double-checked this. It indeed is the problem If I can have a difference of 0.5-0.6V between VCC and SRN, I can trigger a charge cycle.
    Dear can you kindly help with the Fuel gauge part of the problem mentioned above?

  • 0 in reply to Dev
    TI__Guru** 104885 points

    Hello Dev,

    Sorry for the late response, if you have questions about multiple TI products it may be easiest to create a thread for each one so we can assign it to the proper support team, otherwise there may be some delays.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 140 points

    Hi Wyatt,
    Currently, the only issue is with the Fuel Guage BQ27220EVM module. That I believe was what initially the question was about. I have detailed that question in the post above.

  • 0 in reply to Dev
    TI__Mastermind 20221 points

    Hello Dev, 

    Sorry for the delay here. The GPCCEDV tool is a math calculation and simulation tool that helps obtain CEDV coefficients for your specific battery profile. The process for using the GPCCEDV tool is fairly simple and is well documented in the GPCCEDV user's guide. The zip file that the user's guide talks about should just consist of a config file which will tell the tool how to process the data, and you will need to provide 6 different log files (obtained over different temps and different rates, explained in the user's guide). For the information that needs to be included in the configuration file, this is included in section 2.1 Configuration File. For the information needed for the 6 log files and how to collect the data for these log files, please refer to section 2.2 Data Log Files. Once you have collected and created all of the necessary files you can then zip them up together and then upload to the tool (see the image below). 

    Note that you need to name these files exactly the same as they are named in the GPCCEDV user's guide. 

    Once you submit this to the tool, you will get a report with the new data. You will then need to upload this data to the gauge. 

    Regards, 

    Jonny. 

  • 0 in reply to Jonny
    Prodigy 140 points

    Hi ,
    The userguide says "An easy recording method utilizes TI's bqStudio software utility called GPC Packager that reads data
    directly from a TI fuel-gauge" in section 2.2 I cant seem to find this option in bqStudio for logging. Is this guide wrong? Is there some other way to log the charge discharge curves or should I do that manually to generate the required 6 files?

  • 0 in reply to Dev
    TI__Mastermind 20221 points

    Hello Dev, 

    You can manually generate the required 6 log files. I recommend referring to this E2E thread regarding GPC Packager. Additionally, the user's guide describes how to obtain the 3 pairs of log files without the use of a TI EVM or TI bqStudio software. 

    Regards, 

    Jonny.