• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 63 subscribers
  • Views 125 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.

BQ25750: VAC input line protection

Ben
Intellectual 400 points
Part Number: BQ25750
Other Parts Discussed in Thread: EV2400

Tool/software:

Hello TI team,

When I tested the charger board under the following conditions, the IC burned.

- VBAT port : Open (not connected Battery)

- I2C : Connected EV2400 with Laptop

- Charger board : no power condition

- VAC port : is connected to a 48V DC voltage source(active) via a power supply.

The IC burned at the moment when an active 48V DC jack was connected to the charger board.

As you already know my charger board schematic, VAC line doesn't have a lot of capacitance(less than ~2uF)

This scenario (connecting an active VAC line) is a common use case, and needs to be tested repeatedly for reliability.

1. Have you seen a similar case before?

2. Do you have any suggestions for protecting input line and the IC VAC port?

Thank you.

  • +1
    TI__Mastermind 31275 points

    Hello Ben,

    1. I've seen similar cases where this happens with the battery.

    2. I'm looking through your schematic and I have a few recommendations for the ACFETs:

    • You'll need a zener diode to clamp the voltage between ACDRV and ACSRC. (ACSRC is the node attached to the source pin of the ACFETs)
    • I recommend adjusting the RC filter on ACDRV. I recommend the following:
      • Replace R104 with a 10Ω resistor.
      • Install a 10nF cap between ACSRC and ACDRV.
      • You can remove the current RC filter formed by R103 and C123.

    I also have a few recommendations to protect IC from a battery plug-in:

    • Replace R105 with a 10Ω resistor.
    • Install a 10nF cap between BATSRC and BATDRV
    • You can remove the current RC filter formed by R114 and C128.

    Let me know if this is a workable solution for your project and let me know if you have any other questions.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Intellectual 400 points

    Thanks your advice Ethan,

    I will apply solution as below solution

    - Input connector TVS diode (ex. SMAJ78CA)

    - Input Inductor for L-C filter (ex. XAL1060-401)

    - VACFET & VBATFET Gate resistor (10Ω) with 10nF cap between source to gate

    - Remove current R-C filter at the gate line both of VACFET & VBATFET

    If you have any other workaround, let me know.

    Thank you.