• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 2032 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.

BQ77905: The problem that BQ7790502 can recover automatically when fault accurs

Shaw Wong
Intellectual 590 points
Part Number: BQ77905

Hi,

Our customer uses BQ7790502 to protect Li battery, and it can protect battery when SCD, OCD, OTD, OTC, OV or UV occur. The problem is that when fault occurs and the battery is protected, the fault recovers automatically after about 2 ms. Bucause the fault recovery method of BQ7790502 is load removal, so the fault should recover when the load is removed, rather than it recovers automatically.

They tested TI EVM with BQ7790500, on which the fault recover through load removal + delay, and it can keep protection state, and not recover automatically. Then they used BQ7790502 instead of BQ7790500 on TI EVM, however, the fault can also recover automatically. So why BQ7790500 can keep protection state, but BQ7790502 can not keep protection state and recover automatically when fault occurs? I am waiting your reply, thanks!

Note: the screenshot of datasheet of BQ77905 and the customer's schematic as follows.

  • 0
    Intellectual 620 points
    the same problem，waiting an answer...@TI
  • 0 in reply to Comet Yes
    TI__Guru 54715 points
    Hi Shaw and Comet,
    Load detect is based on the LD pin moving to a voltage above its threshold. It is connected to P- through the R9 shown above. After the device protects, if P- and LD do not go high before the tLD_DEG (LD detection de-glitch) time the part will recover if the UV or OC condition is also removed. The 2ms time described is consistent with this time. To recover the pin must go below the recovery threshold, and the part has the RLD_INT pull down to help cause recovery.
    If there is no load on the system or EVM, or a high capacitive load with little load, the P- and LD pin may not move and recovery may be very quick as you report. The default part on the EVM is -00, if a -02 part does not remain protected in the same test setup with the EVM, check that the pin is properly soldered and that the LD resistor and trace are not damaged. If all connections are proper and PACK- and LD are rising, the part must be damaged.