• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 553 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.

BQ40Z60: Using same contacts for charging and discharging

Thomas Albrecht46
Prodigy 240 points
Part Number: BQ40Z60


Hi,

I'm designing an application where the cells of the system are either getting charged or discharged. Now I would like to have one connector for charging and discharging instead of two (J1, J5 respective on the EVM). I would use the LM74610 to block current off from VSYS in the case an external power is supplied.

When there is no external power supplied the VAC would be equal VSYS. Because of the body diode the ACFET does not seperate VAC from VSYS but HIDRV Mosfet Q8(EVM) of the Buck-Converter should do the job.

What are the conditions that the HIDRV Mosfet is OFF? I've found some stuff concerning the ACFET which seems to be only ON when VCC > HSRP? Then I've read that the minimum supply voltage must be at least 1V above VBAT/VSYS? Maybe you have some specific conditions for me. All in all I wonder whether it is not possible to simply connect VSYS and VAC without any changes respectiv the EVM. Should be similar to the event VAC < VSYS.

Some small additional questions:

- PIN14 is in my design not connceted. As I dont use the pre-charge feature nor the syspres this should be fine, right?

- During charging I would like to have the Gauge LED constantly on. Does it work to pull PIN15 constantly low during charging or is this an external interrupt which is blocking other functions?

I've added a schematic. The interesting part is on the right hand side.

Thank you very much

Best regards,

Thomasbms_einseitig.pdf

  • 0
    TI__Mastermind 34775 points
    Hi Thomas,

    I will review your schematic and respond shortly.
  • 0
    TI__Mastermind 34775 points

    Hi Thomas,

    Your schematic using LM74610 (Zero IQ Reverse Polarity Protection Smart Diode Controller) looks like it would work. The HIDRV wouldn't switch if ACFET isn't ON, which requires VCC > VHRSN where VHRSN is the VSYS (essentially battery voltage). 

    Here's the info from page 23 of the bq40z60 datasheet:

    8.3.2.3 FET Drive

    The bq40z60 controls two external N-CH MOSFETs in a back-to-back configuration for battery protection. The charge (CHG) and discharge (DSG) FETs are automatically disabled if a safety fault is detected and can also be manually turned off using AFE_CONTROL[CHGEN, DSGEN] = 0, 0. When the gate drive is disabled, an internal circuit discharges CHG to BAT and DSG to HSRN.

    The AC FET (N-CH MOSFET) controls power input from the AC adaptor to the battery charging system by monitoring the voltage at the VCC pin, and turning ON the ACFET if the voltage exceeds the VHSRN voltage. The following register command sets the AC FET gate drive output control, AFE_STATUS register (0x01) ACFET (BIT 2): Setting this pin to 1 allows the AC FET gate drive to be on if other conditions are satisfied.

    PIN14 seems to be used as SYSPRES. Unfortunatel, FETs are not recommended for use on this pin because they can cause false system detection when there's no system present (parasitic capacitance). We recommend a direct connection to VSS (your GND) or setting NR bit in the DA configuration register to 1.

    LED display only detects the low to high transition of pin 15 to turn on the LED and keeps the LEDs on for a max LED config setting of 16sec. You will need to continuously toggle pin 15 for the LED to stay ON during charging.

  • 0 in reply to Damian Lewis
    TI__Mastermind 34775 points
    Hi Thomas,

    For LED to display during charge Settings >> LED Configuration[LEDCHG] = 1

    LEDCHG (Bit 2): LED Display During Charging
    1 = Enabled
    0 = Disabled