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LM66100: Using with 3 power sources

Prodigy 40 points

Replies: 7

Views: 131

Part Number: LM66100

Hello,

I want to use LM66100 with 3 battery. It is working when I connect 2 batteries. But when I connect 3th battery, total current goes up, and current flow from battery to battery. Is there any problem on the following schematic?

  • Hi Burak,

    I see you have an Or-ing circuit built for three voltage inputs. Can you please describe your test case further (what order the inputs are connected). It is important we know the sequence of events to narrow down our support.

    When you say "total" current goes up, do you mean total load current? And also you are noticing current flow to and from what inputs?

    Best Regards,

    Shreyas Dmello

    To find the latest information on Power Switches, visit www.ti.com/powerswitch

  • In reply to Shreyas Dmello:

    Hi Burak,

    Just want to follow up on this thread. Have you worked around you issue?

    Best Regards,

    Shreyas Dmello

    To find the latest information on Power Switches, visit www.ti.com/powerswitch

  • In reply to Shreyas Dmello:

    Hi again.
    I have tested the system. The description is the following.
    I have a power supply with 2 outputs. And I have a 18650 battery. Power supplies output has own ampere meter.
    I have connected Vin1 input of circuit to power supplies first output.
    I have connected Vin2 input of circuit to power supplies second output.
    I have connected the Vin3 input of the circuit to the battery. And I have connected amperemeter and voltmeter on this input. The following measurements are get when voltage change slowly. (about 100mV step/s) They are expected results.

    Step Vin1 Vin2 Vin3 I1 I2 I3
    1 3,603 3,606 3,716 4mA 2mA 29mA
    2 3,803 3,606 3,716 29mA 2mA 0
    3 3,703 3,606 3,72 8mA 2mA 23mA
    4 3,803 3,806 3,716 29mA 2mA 0
    5 3,803 3,906 3,716 4mA 29mA 0
    6 3,803 3,806 3,716 29mA 2mA 0
    7 4,03 3,906 3,716 29mA 2mA 0
    8 4,603 4,706 3,716 4mA 29mA 0
    9 3,603 4,706 3,716 4mA 29mA 0

    But, when I change voltage faster (about 500mV/s) results are changed. The following results are gets when I move the knob of power supply rapidly.

    Vin1 Vin2 Vin3 I1 I2 I3
    3,903 4,106 3,716 "-29mA" 60mA 0

    But, when I change voltage faster (about 500mV/s) results are changed. The following results are gets when I move the knob of power supply rapidly.

    I think U18 and U16 are on state during same time. Maybe response time of LM66100 is slow.
    I have changed the circuit. I have added 3 additional LM66100. I think this circuit can blocking reverse current. But my application is low power application so this is not my first choice.

  • In reply to Burak Selamlar1:

    Hi Burak,

    I do not think U15, U17 and U19 will turn on due to the low voltage difference between the output and input. I would not recommend this.

    Could you please probe the input of U16 and the input of U18? I would like to see the voltage on those nodes during this reverse current event.

    Best Regards,

    Shreyas Dmello

    To find the latest information on Power Switches, visit www.ti.com/powerswitch

  • In reply to Shreyas Dmello:

    Hi,
    I have measured the input voltage of U16 and U17 during the reverse current events.

    I have connected Vin3 input of circuit to power supplies first output.
    I have connected Vin2 input of circuit to power supplies second output.
    I have connected the Vin1 input of the circuit to the battery.

    Measurement results are the following.

    Vin1 Vin2 Vin3 I1(mA) I2(mA) I3(mA)
    4,2 3,2 4,4 -110 0 139

    Input of U18 : 4,335V
    Input of U16 : 4,357V

    After this measurement, I have disconnect battery(Vin1) and measure again,

    Input of U18 : 4,388V
    Input of U16 : 4,397V

    I think, U18 is on state still.

    I have changed R44 and R42 to 100kR. After this modification, circuit characteristic has changed. Now, every time occurs reverse current.

  • In reply to Burak Selamlar1:

    Reverse current flow stops when I touch R44-U18.5. What is the ideal value of R44 and R42? I experience this problem more often when I increase R44 and R42.

  • In reply to Burak Selamlar1:

    Hi Burak,

    From your measurements, I think we can confirm that both LM66100s are on at the same time. 

    What is strange is that this works when you are changing voltages slowly but does not when the voltage rises quickly.

    When you are increasing the voltage "quickly" are you sure that there is no overshoot from the supply?

    Before you raise the voltage on the supply, the battery(VIN1) was powering the output, correct?

    Can you share any voltage waveforms that describe this event?

    Edit 10/25: Have you managed to work around your issue?

    Best Regards,

    Shreyas Dmello

    To find the latest information on Power Switches, visit www.ti.com/powerswitch