• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 62 subscribers
  • Views 132 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

Original question:

BQ76952: I2C Communication Failure

BQ76952: i2c failure

MounishPatel Seetha
Intellectual 660 points
Part Number: BQ76952
Other Parts Discussed in Thread: STRIKE

Hi,

Out of every 100 boards we make, 1 results in i2c Failure while assembling the device to the battery pack. Following are complete details

Battery Pack : 60V

Charge Pump Capacitor : 0.47uF 100V

Bat Pin Capacitor : 1uF 100V and 100pF 100V 

RBAT : 100R , Followed by 100V Diode

Post Damage observation:

  • Bq76952 IC heating up ( 0.003 Current consumption with only TI IC on board )
  • Reg18 voltage is 0.2V not 1.8V like other devices. 

I suspect that bq76952 is damaged. I would like to know what is causing this damage. I am attaching my schematic for your reference. Please check

I am not using D4 Bidirectional TVS diode as of now, but i gave foot print for future use. will a unidirectional TVS diode at this point solve issue?

Edit: I found a capacitor ( 2.2uF 25VDC) at Reg18 pin was short. When replaced with a new one. Communication resumed. 

  • 0
    TI__Mastermind 35150 points

    Hello Mounish,

    I am glad to hear that you found what component failed and that the part was working correctly afterwards. 

    Yes, I'd definitely recommend that you add TVS diodes on any location where an ESD strike may occur. Does your assembly follow ESD safety methods?

    Could the capacitor have been damaged before assembly? Or was the capacitor damaged at a later point?

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Intellectual 660 points

    Hello Luis H.S

    We follow minimalistic ESD methods. Do you think this is an ESD failure?

    No, Device worked for couple of cycle, it failed later.

    Do you recommend to add TVS diode at Reg8 pin or Bat Pin?

  • +1 in reply to MounishPatel Seetha
    TI__Mastermind 35150 points

    Hello Mounish,

    I find it strange that only a single capacitor was damaged. Not sure if it was ESD or something else, but it is good practice to add ESD-related components.

    REG18 typically does not need a TVS unless you see a dangerous transient there. It may be better to have these elsewhere, like BAT or the communication lines.

    We have the following document that shows what types of ESD tests we've done and some recommendations for ESD-robustness:

    BQ76942 IEC ESD 61000-4-2 ESD Test Report

    Best Regards,

    Luis Hernandez Salomon