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LM3489: LM3489

Nirali Shah
Prodigy 10 points

Part Number: LM3489

Tool/software:

LM3489QMM/NOPB: Request to check the circuit

Part Number: LM3489QMM/NOPB

Product Link

I would like you to check the circuit.

Input voltage: 5V , 12V , 24V (Battery , USB , Adapter)

Output voltage: 5V, 9V, 15V, 20V

Output current: 3A , 5A (As per the PD2.0/3.0) charging profile . 

 Vin = 5V , 12V , 24V (Battery , USB , Adapter)

Vout = 5V

I_out = 6A

Kindly check that the value of Radj , Specs of Mosfet and Inductor are suitable to my requirement or not .

Second Circuit using the same part .

Vin = 5V , 12V , 24V (Battery , USB , Adapter)

Vout = 5V

I_out = 6A (Fixed)

Can i use the same part of Mosfet and inductor for my second circuit also ?

Kindly check that the value of Radj , Specs of Mosfet and Inductor are suitable to my requirement or not .

 

Is there any point which i have missed while designing it ? Kindly check the circuit and let me know .

Thanking You

Shah Nirali

  • 0
    TI__Mastermind 23635 points

    Hi Shah,

    For this portion of the circuit, is there anyway to minimize how large you are making the FB node? That's a lot of things connected to it, and it's quite a sensitive pin. Also C23 may cause the part to behave unexpectedly. I haven't ever seen a capacitor on FB before.

    On the EVM's we have a ladder system like below

    Thanks,

    Andrew

  • 0 in reply to Andrew Kutzler
    Prodigy 10 points

    Hi Andrew , 

    Thank you for addressing my query .

    I have taken the reference from the TIDA-050014 (Ti-Evm board)

    I need to control the various outputs as per my Slave device requirements . If my device works on 5V , i will keep all PDO off, if it works on 9V i will on PDO1 and further it will be continued . This on off of PDO is controlled by MCU. 

    So i have connected three Mosfet for switching purpose .

    Thanks

    Nirali Shah 

  • 0 in reply to Nirali Shah
    TI__Mastermind 23635 points

    Hi Nirali,

    I see now that in https://www.ti.com/lit/pdf/slvubj5 we use what you have put on your design.


    I still think something like below would be better. FB is a sensitive pin that can cause errors when external noise is added to the pin. This can easily happen when other signals pass by on neighboring layers when FB is large.

    However, the default inductor in that design is not big enough. I'd recommend something that has at least 8.5A of saturatiuon current (what I calculated your current limit to be)

    Thanks,

    Andrew

  • 0 in reply to Andrew Kutzler
    Prodigy 10 points

    Hello Andrew,

    I cannot use one Mosfet (PDO) to select different outputs . So i have used 3 Mosfet's for individual voltage output . At a time any of one will only be ON and other two will be OFF . 
    My approx output power will be 60 Watt or 100 Watt .

    For 60 Watt , i have selected the inductor AMRM00101040100MA1 Inductor . 
    If i want to take 100 Watt , then i may need to change it to  inductor having 8.5A of saturatiuon current .

    Am i correct ? 

    Also review my both the schematic and give your inputs .

    Thanks
    Nirali Shah

  • 0 in reply to Nirali Shah
    TI__Mastermind 23635 points

    Hi Nirali,

    You schematics are fine aside from the comment I had about the FB node. I understand what you are trying to do, but just note that FB is a sensitive node, so excessively large FB nodes are more susceptible to picking up noise and making your circuit unstable. It's ok if there's high impedance between VOUT and FB, but FB should be kept to a minimum size. If you are ok with FB picking up some unwanted noise, then it's ok to have those FET switches.

    The EVM's FB pin while not ideal is kept to a relatively minimum size. Your FB node is connected to source of 3 different MOSFETS,

    AMRM00101040100MA1 should work for the 60W design and you'd definitely need a different one for the 100W design.

    Thanks,

    Andrew

  • 0 in reply to Andrew Kutzler
    Prodigy 10 points

    Hello Andrew,
    Geetings.!!!!

    Yes sure , i will consider your inputs and work accordingly.

    Meanwhile can you check the Radj value which i have used is suitable as to my requirment or not .

    For both the circuit . Variable DC-DC and buck of 6A .

    Thanks

     Nirali 

  • 0 in reply to Nirali Shah
    TI__Mastermind 23635 points

    Sounds good Thank you!

    I'm going to close the thread now.

    Thanks,

    Andrew