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LM74700-Q1: LM74700 Or-ing configuration

Mike Jung
Intellectual 700 points
Part Number: LM74700-Q1
Other Parts Discussed in Thread: TPS2663, TPS2660, TPS2120

Dear TI engineer.

I have questions about using the Or-ing system.

1) What are the functional differences other than the electrical characteristics of the LM74700-Q1 and LM5050-Q1?

If you choose one of the above devices and use the enable pin with Or-ing to get one power source.

2) Using one control signal, input the enable pin. Is there a problem if you connect the single inverter to one of the enable pins?

    - I'd like to ask if there is a way to implement it in one control pin.

3) One of the two becomes enable off. Isn't this the power supply through the body diode of the FET?

    - If it's powered at the same time, is there a way to deliver only one power source?
    

Thanks.

  • 0
    TI__Genius 16305 points
    Hi,

    Based on the questions posted, your requirement is for power mux design and not ORing.
    ORing involves ORing power rails with same voltage range. Higher voltage will always power the load.

    Please have a look at TI application note on Power mux with priority.

    "www.ti.com/.../slva811a.pdf"

    and

    "www.ti.com/.../slvae51.pdf"

    If your power or load current requirements are higher, let us know we can help you.

    For >30V, 6A power muxing, we recommend TPS2663 device which is released now.
    For >30V, 2A we recommend TPS2660.

    Regards,
    Kari.
  • 0 in reply to Karikalan Selvaraj
    Intellectual 700 points

    Thank you for your reply.

    I have additional questions.
    The voltage level of both sources is approximately 13V, and the load current is max. 1.8A.

    With the TPS2120, it will be simpler to implement than below device.
    Is there any problem with selecting two sources for control of SEL pin?

    Thanks.

  • 0 in reply to Mike Jung
    TI__Genius 16305 points
    Hi

    Yes for 13V 1.8A application TPS2120 is best.
    If i understand your question on SEL pin, you would like to control SEL pin with two select sources?


    Regards,
    Kari.
  • 0 in reply to Karikalan Selvaraj
    Intellectual 700 points

    Thank you for your reply.

    I want to select source with SEL pin only.
    "If the volume on SEL drops too VREF, then the device will switch to IN1 as"
    Long as PR1>VREF," it says. However, Figure 20 & 22 shows PR1 in GND.

    Ask if the source selection is possible with SEL pin level only and how the PR1 pin should be connected.

    Thanks.

  • 0 in reply to Mike Jung
    TI__Genius 10855 points

    Hi Mike,

    Thanks for reaching out to Kari. To introduce myself, I am the Applications Engineer supporting the TPS2120.

    To answer your question, the comparison of SEL to VREF determines which input is the output. If SEL is higher than VREF, then IN2 is the output. 

    In this case, PR1 should be connected higher than VREF. Therefore, if SEL goes below VREF, the device will switch back to IN1.

    You can refer to the Truth table in Table 2 for more information. Looking at row 5 and row 3, the truth table explains the functionality described above.

    Thanks,

    Arthur Huang

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

    Please click "This resolved my issue" button if this post answers your question.