• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 64 subscribers
  • Views 1271 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.

BQ76952: PACK and LD pin functionality question

Eohan George22
Intellectual 620 points
Part Number: BQ76952

Hi, 

If a fet is NOT used to disconnect Bat from Pack+ , 

  • Can LD or PACK pin be used to detect a charger and wake the chip from shutdown mode when its connected by looking at the rising edge ? 
  • Can LD pin left floating if its not used? Any issues with leaving it floating ? 
  • Should PACK pin left floating ? Any issues with leaving it floating ? 
  • Section 13.3 of datasheet, says. "If the PACK pin voltage is higher than the top-of-stack voltage by more than a programmable delta and the top-of-stack voltage is less than a programmed threshold, the device will exit SLEEP mode." . What is the intention of the second condition, when its less than a programmed threshold ? 

  • 0
    TI__Guru 54715 points

    Hi Eohan,

    1. LD has a wake up circuit, see VWAKEONLD in the BQ76952 in section 13.5 SHUTDOWN Mode and others.  PACK does not have a wake function.

    2. If LD and the high side DSG driver are not used it can be tied high or low as described in the data sheet section 16.6 Unused Pins.  The part does have pull ups and pull downs on LD in different modes as described in various sections.

    3. PACK is an input pin but is not included in section 16.6.  PACK can be tied high or low.

    4. Section 13.3 Sleep Mode describes the mode and entry and exit conditions which have options, one being sensing a charger present through the PACK pin voltage, most applicable for high side FETs. In figure 13-1 note the "charger detected" for sleep exit, the voltage on PACK pin condition is different than the "Charger detection" voltage on LD to exit shutdown, the wording is similar but the function is different, it can be confusing.  The second condition with the PACK voltage less than the programmed threshold would be excluding charger detection.  If the threshold is set appropriately connecting a charger that is less than the battery voltage would not wake the device from sleep. 

     

  • 0 in reply to WM5295
    Intellectual 620 points

    WM5295 said:

    Hi Eohan,

    1. LD has a wake up circuit, see VWAKEONLD in the BQ76952 in section 13.5 SHUTDOWN Mode and others.  PACK does not have a wake function.

    But the VwakeonLD does not work without a FET. the voltage is 1.1v. So any battery will wake it up.  Is that correct ? 

    WM5295 said:

    2. If LD and the high side DSG driver are not used it can be tied high or low as described in the data sheet section 16.6 Unused Pins.  The part does have pull ups and pull downs on LD in different modes as described in various sections.

    When LD was tied to Pack+ with a 10k resistor, it prevented the BQ from being shutdown. 

  • 0 in reply to Eohan George22
    TI__Guru 54715 points

    Hi Eohan,

    If LD is tied to the battery voltage with a 10k resistor the part will wake up.  You will not be able to shut it down.