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LM66100: LM66100 ideal diode is not working as expected

udhay kumar
Intellectual 275 points
Part Number: LM66100
Other Parts Discussed in Thread: TPS2116

Hi,

I am planning to use LM66100 ideal diode for a battery powered application where I need to use two batteries in ORing configuration.

Before implementing the circuit in the actual product, I tested it with a lab power supply. I kept the one power supply at constant 3.0V and adjusted the other power supply below and above the 3.0V level.

When I going above 3.0V range with 100mV step increment (3.1V) , the ORing circuit output in drop to 2.7V. If the voltage increased one step further (3.2V), the total output following the input as 3.2V.

The same for opposite, if the voltage decreased to 2.9V the output stays at 2.7V and if the supply further decreased to 2.8V, now the output follows the 3.0V supply.

Note that the both cases I kept the one of the supply at 3.0V without changing, so as per the circuit operation there should not be a 2.7V output.

So at this case is it creating a circulating current inside the two power supplies. What will happen in the real time situation with batteries?

Here I uploaded a private YouTube video for your reference

https://youtu.be/6ncPc5nnl7s

  • 0
    TI__Genius 15665 points

    Hi Kumar, 

    Ideal Diode ORing is strictly intended to choose the highest voltage supply. If priority of one supply is required, a power mux is needed to select and prioritize one input. I would recommend the TPS2116. Since an ideal diode ORing configuration will simply choose the highest supply, for your case, this means the LM66100 will be in a constant evaluation of which 3V supply is higher. 

    If both devices are on, due to the voltage supplies being inherently different, along with the Ron variability of each device, the supplies will attempt to balance themselves, likely triggering a reverse current event. By causing the FETs to run between their VIL and VIH, you will experience unpredictable, possibly on, possibly off states in your switches. If both switches are disabled, you would see 3V-VfWD. As you can see the output does not stabilize until there is enough difference between the two supplies.

    This is why power muxing is needed for your application. With a power mux, you can select the priority input, even with two supplies at the same voltage. 

    Best Regards, 

    Elizabeth