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LM62460-Q1: circuit issue - LM62460-Q1 Not stable

yuval andorn
Prodigy 10 points
Part Number: LM62460-Q1
Other Parts Discussed in Thread: LM62460

Hi 

im trying the attached circuit on my PCB: On my first PCB the circuit does not work as expected,  i receive 2.8V rather than 5V and the reset pin is low indicating that the IC is fault state. 

in a second PCB i have seen that the voltage rise above 5V and is not being regulated. 

my BOM is very similar to the attached BOM. im not sure if this issue is because my components does not match ? or it might be some kind of other issue. please advise what i should look for to see what can cause the device instability.

thanks

yuval 

5824.WBDesign30.pdf

  • 0
    TI__Guru 50120 points

    Hi,

    Are you using a fixed or adjustable variant of the LM62460? From your WEBENCH design, it looks like you have tied FB directly to VOUT. 

    Can I assume that you are using the LM62460Q5RPHRQ1 on your PCB design?

    Can you doublecheck to make sure your input supply isn't current limited?

    Also can you provide the PCB layout or a top view image of your PCB for review? Confirm that all components are soldered on properly with appropriate solder paste. 

    From a cursory glance at your design, there doesn't appear to be anything striking/odd about this circuit.

    Regards,

    Jimmy 

  • 0 in reply to Jimmy Hua
    Prodigy 10 points

    Hi Jimmy

    im using adjustable variant of the LM62460, i have attached the wrong WBdesign.

    below is the design is according to WBdesgin.

    ill check my components again.

    thanks

    yuval

  • 0 in reply to yuval andorn
    TI__Guru 50120 points

    Hi Yuval,

    Please provide the correct schematic so I know what each value is. 

    Looking at your PCB layout image, can you confirm if you have GND pour on the top layer? It looks like the PGND pin 1 and 15 go to inner layer.

    It is important to have GND on the layer of where the switching IC is placed to help with thermal flow and short ground loop. 

    Refer to Section 11.2 for a layout example.  

    Regards,

    Jimmy