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Original question:

LM5069: LM5069 as a bidirectional switch?

LM5069: Current limit on reverse current

Sharina
Prodigy 150 points
Part Number: LM5069

Tool/software:

I am planning to use LM5069MM-1 as a bidirectional switch controller driving 2 anti-serial or back-to-back MOSFETs, the sources of both FETs are connected together and to OUT pin, while both gates are connected together to GATE pin.

My intention is the following: 

Current flowing from VIN to VOUT: Have all functions working (UVLO, OVLO, Current limit, Power limit)

Current flowing from VOUT to VIN: Keep only current limit and Power limit

In reverse current, the VIN-SENSE will be negative but will not exceed the absolute max of +/-0.3V. Can the controller turn off the MOSFETs on current limit for either forward or reverse current flow?

  • 0
    TI__Mastermind 39820 points
    Sharina said:
    Current flowing from VOUT to VIN: Keep only current limit and Power limit

    This can't be achieved by LM5069. Even none of our hot-swap controller can support this functionality. 

  • 0 in reply to Avishek Pal
    Prodigy 150 points

    If I connect 2x LM5069 back-to-back in the configuration below, can I achieve the current limit protection for current flowing from VOUT to VIN?

    Both LM5069 are enabled by the same signal from MCU, VIN is on the left side and VOUT on the right side. Once VIN available, Q1 will turn on with its soft-start (D1, Q3) and Q2 body diode will conduct. Once voltage available at VOUT, the right LM5069 will turn on Q2 with its soft-start (D2, Q4).

    On forward overcurrent fault (left to right current flow), left LM5069 will turn off Q1 and eventually right LM5069 will turn off Q2 because there's no voltage detected on its pin 2.

    On reverse overcurrent fault (right to left current flow), right LM5069 will turn off Q2. However, Q1 is still on and Q2 body diode can conduct. How can I make the left LM5069 also turn off Q1, tying the PGD of the right LM5069 to the UVLO of the left LM5069? Will this cause issue on startup, where both LM5069 not able to drive Q1 and Q2?

  • 0 in reply to Sharina
    TI__Mastermind 39820 points

    Schematic looks fine. Please implement in the hardware and test the functionalities.