• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 322 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.

BQ76952: OVP protection not operating

Swapnil Said
Prodigy 30 points
Part Number: BQ76952
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

Hi,

I am facing an issue with BQ76952 device regarding OVP protection. When we try to test the OVP protection, We raise the voltage for a cell above 4.0V, which is the threshold for OVP. We are also ensuring that the current is positive, which means the device is in charging mode. When the cell 6 voltage crosses the threshold, we get OVP status flag, OVP protection flag and OVP protection latch flag set. But the Charge MOSFET remains ON. It does not switch of although the protection is enabled. after about 5 seconds, we get PF depending on the situation, sometimes OVP Permanant failure flag or sometime Charge FET protection Permanant failure. But we are not getting the charge MOSFET turn off when OVP error has happened. 

following is a screen grab for failure. In this screenshot, we can see that the MOSFETS are turned Off but they are turned off due to PF, after 5 seconds. Not when the OVP protection fault was raised, or latch was raised.

In First Screen I have highlighted the Cell 6V. (The issue is not with cell 6, but with all the cells. we just happen to check with cell 6 while getting the screen shot)

We have highlighted CC3 current, And the FET status.

In the below screenshot we can see the Cell overvoltage protection and cell overvoltage latch flag set.

In below screenshot, we can see the Charge FET protection permanent failure has been set.

Below are my settings regarding the OVP protection and Charge FET.

Class Subclass Address Name Type Actual Value Units Configuration Value (Hex)
Settings Protection  0x925F Protection Configuration  H2 0x0112 Hex 0x0112
Settings Protection  0x9261 Enabled Protections A U1 FC Hex 0xFC
Settings Protection  0x9262 Enabled Protections B U1 F0 Hex 0xF0
Settings Protection  0x9263 Enabled Protections C U1 F6 Hex 0xF6
Settings Protection  0x9265 CHG FET Protections A   U1 98 Hex 0x98
Settings Protection  0x9266 CHG FET Protections B   U1 91 Hex 0x91
Settings Protection  0x9267 CHG FET Protections C   U1 56 Hex 0x56
Settings Protection  0x9269 DSG FET Protections A   U1 A4 Hex 0xE4
Settings Protection  0x926A DSG FET Protections B   U1 E6 Hex 0xE6
Settings Protection  0x926B DSG FET Protections C   U1 E2 Hex 0xE2
Settings Protection  0x9273 Body Diode Threshold    I2 50 mA 0x32
Settings Alarm  0x926D Default Alarm Mask    H2 F800 Hex 0xF800
Settings Alarm  0x926F SF Alert Mask A   U1 0xFC Hex 0xFC
Settings Alarm  0x9270 SF Alert Mask B   U1 0xF7 Hex 0xF7
Settings Alarm  0x9271 SF Alert Mask C   U1 0xF4 Hex 0xF4
Settings Alarm  0x92C4 PF Alert Mask A   U1 0x5F Hex 0x5F
Settings Alarm  0x92C5 PF Alert Mask B   U1 0x9F Hex 0x9F
Settings Alarm  0x92C6 PF Alert Mask C   U1 0 Hex 0x00
Settings Alarm  0x92C7 PF Alert Mask D   U1 0 Hex 0x00
Settings Permanent Failure 0x92C0  Enabled PF A   U1 0xDF Hex 0xDF
Settings Permanent Failure 0x92C1  Enabled PF B   U1 0x02 Hex 0x03
Settings Permanent Failure 0x92C2  Enabled PF C   U1 0x03 Hex 0x03
Settings Permanent Failure 0x92C3  Enabled PF D   U1 0x02 Hex 0x01
Settings FET  0x9308 FET Options  H1 0x19 Hex 0x19
Settings FET  0x9309 Chg Pump Control U1 0x05 Hex 0x05
Settings Current Thresholds 0x9310 Dsg Current Threshold I2 65 A 0x0064
Settings Current Thresholds 0x9312 Chg Current Threshold I2 65 A 0x0064
Protections COV  0x9278 Threshold   U1 3 V 0x50
Protections COV  0x9279 Delay   U2 150 ms 0x2B
Protections COV  0x927C Recovery Hysteresis  U1 2.9 V 0x02
Protections COVL  0x927D Latch Limit  U1 10 NA 0x0A
Protections COVL  0x927E Counter Dec Delay U1 8 Sec 0x08
Protections COVL  0x927F Recovery Time  U1 10 Sec 0x0A
Permanent Fail  SOV 0x92CE  Threshold  I2 4500 mV 0x1194
Permanent Fail  SOV 0x92D0  Delay  U1 5 Sec 0x02

Please let me know if I am failing in some settings, or not testing it correctly.

  • 0
    Prodigy 30 points

    Additional Data

    Permanent Fail  CFETF 0x92EE  OFF Threshold I2 20 mA 0x14
    Permanent Fail  CFETF 0x92F0  OFF Delay U1 5 Sec 0x05
    Permanent Fail  DFETF 0x92F1  OFF Threshold I2 -20 mA 0xFFEC
    Permanent Fail  DFETF 0x92F3  OFF Delay U1 5 Sec 0x05
  • 0 in reply to Swapnil Said
    TI__Genius 17945 points

    Hello Swapnil,

    Can you share a .gg file from bqStudio as well as a screenshot of what you see from that? Also, do you know if the CHG FET is turning OFF and then back ON after OVP is triggered but before Permanent Fail is triggered? A waveform from an oscilloscope can help verify that.

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Prodigy 30 points

    Hi Alexis,

    unfortunately, I am not working with BqStudio. I am testing the PCB using CAN messages only. 

    do you know if the CHG FET is turning OFF and then back ON after OVP is triggered but before Permanent Fail is triggered?

    - We have checked if the Charge MOSFET turns off, we have found that the Charge MOSFET only turns off after permanent fail. I hope you meant the Charge FET gate waveform. I will arrange it.

  • 0 in reply to Swapnil Said
    TI__Genius 17945 points

    Hello Swapnil,

    Thank you for clarifying how you are communicating with the device. bqStudio would make it a lot easier for us to ensure your settings are set correctly.

    Swapnil Said said:
    - We have checked if the Charge MOSFET turns off, we have found that the Charge MOSFET only turns off after permanent fail. I hope you meant the Charge FET gate waveform. I will arrange it.

    I did mean the Charge FET gate waveform. I look forward to what you share.

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Prodigy 30 points

    Hello Alexis,

    We had some issues with the test setup. We were trying to test the fault in Charge mode, which was not set up correctly. The current direction was in discharge more only, which allowed current through the body diode and would switch off only when the Discharge MOSFET is turned off because of the PF protection.

    Sorry for the delay in replying. I will let you know when we are ready with the setup, and we are able to test.

  • 0 in reply to Swapnil Said
    TI__Genius 17945 points

    Hello Swapnil,

    Thank you for letting me know. I hope your testing goes well with your new setup.

    Best Regards,
    Alexis