• State Resolved
  • Locked Locked
  • Replies 54 replies
  • Subscribers 63 subscribers
  • Views 9971 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ40Z60EVM - the charger voltage rises too high in the constant voltage region

Sergey Antsupov
Intellectual 545 points
Other Parts Discussed in Thread: BQ40Z60EVM-578, BQ40Z60, BQSTUDIO, EV2400

Hello, Thomas,

I have started lately with a brand new BQ40Z60EVM-578. The PCB has a label Rev A on it, the firmware is v0_13_build19. The pack is 2s LiPol 9.7Ah, learning cycle fulfilled successfuly.

My problem is: for some reason the charger characteristic isn't flat enough in the constant voltage region and the pack voltage tends to rise in excess of 300mV over the programmed level. Actually I never allowed the charger to fully complete the cycle with initial settings even as low as 4075mV for fear to drive the pack overcharged. I can accomplish charging with FC and no heartache only by issuing several tiny manual voltage corrections in the course of it. Luckily these data flash writes have an immediate effect. Please help me make charging controllable. I attach zip with registers and data flash contents (hope I did it right;-)

bq40z60.ZIP

Please let me also ask for some clarifications, regarding Technical Reference Manual sluua04:

  • CHG_FET bit mentioned at p.63,68 is missing from FET Options table p.153, but shows in bqStudio
  • CHGIN bit mentioned at p.68-69 is missing from both FET Options table p.153 and bqStudio
  • No formulae for calculation nor definition of LCHG Current Resolution
  • PCHG_COMM bit mentioned at p.67 is not found elsewhere
  • ChargingConfiguration[LCHGM] function needs clarification
  • PF Shutdown Voltage/Time at p.75 - no definition found
  • IT Gauging 2 Configuration at p.153 - no definition found
  • initially BTP_INT bit was stuck set despite of BTPCharge/DischargeSet() commads, but it changed at some point and now the commands have effect - what can keep the bit from clearing?
  • does BTP pin reflect only configured BTPCharge/DischargeSet() events and no others? (I'm a bit confused with a pin name ALERT in datasheet.) Can a slight pull-up be switched off from the pin?

And at last I report a slight (at room temperature) influence of LED display on temperature measurement in EVM: 1uF capacitors and  330kOhm resistors give about 2K swing as the LEDs blink. I removed the capacitors from EVM and try to ignore the resulting visual effect.

Thank you very much.

Sergey

 

  • 0 in reply to Sergey Antsupov
    Intellectual 545 points

    Thomas,

    let me inform you of the results I managed to obtain so far.

    1. Now I can control the charging voltage within millivolts. I discovered small regions of saturation near the minimum and maximum possible values of the Charger Voltage Register, which poorly affected my calculations. With two measurements somewhat shifted away from those regions REAL Minimum Voltage Output and Voltage Resolution can be resolved. Those values show enough dispersion among available samples of bq40z0, but being individually accounted for become harmless. Their temperature stability is still to be investigated however. I suspect that the charger uses internal reference voltage divider which is supposed to have equal lower and upper halves. But in fact the halves are not equal, which leads to a) the constant in the formulae being different from 610mV and b) the Voltage Resolution being different from MVO/256.

    2. Temperature measurement with external sensor shows decent behavior down to -30C, which is enough for me now. I have noted a new tool for temperature compensation optimization in the product folder. Going to explore it soon since low temperature is vital for my project.

    And lastly, I ask you to reveal the detaied procedure of srec file programming since I feel the chances are great that we will have to update our devices in the field.

    Regards,

    Sergey

  • 0 in reply to Sergey Antsupov
    TI__Guru 73830 points

    Sergey,

    Thanks for the update. The srec files use the Motorola SREC format and the addresses in the file. You can also use this document for reference in programming the data flash.


    Tom

    Bq40z50 Data Memory Programming for Mass Production.pdf

  • 0 in reply to ThomasCosby
    Intellectual 545 points

    Thank you,

    but I think there must also be some commands to be sent BEFORE and AFTER srec programming (may be set ROM mode, execute new firmware and/or something else).

    Please let me know if there are any and their format.

    Regards,

    Sergey

  • 0 in reply to Sergey Antsupov
    TI__Guru 73830 points

    The device can be placed in ROM mode by writing 0F00 to The MAC register 00. The device can be returned to normal mode by sending SMB command 08.