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TPS61240: TPS61240

Part Number: TPS61240

Dear,Sir 

I am using TPS61240 IC in our project.I am facing issues related to the feed back path diode .

And due to that i am not getting the desired output.

If i replace the shottkey diode with 0E resistor i am getting proper output.

I am attaching the developed schematic,Please have a look.

New Schematic : 

New Schematic :

Layout Details : 

Please help me on the above situation..!!

  • Hi,

    I read about your description, and there is one point I want to figure out. What kind of  undesired output you refer to ? Do you have oscilloscope screenshot? Thanks.

  • Undesired Output means the output fluctuates  from 0 to 9 V around and that also not stable.

    Ok,Will provide you the Oscilloscope screenshot soon..!!

    Thanks..!!

  • Dear,

    Please Find the images captured from the oscilloscope.

    Hope this helps.

  • Hi,

    I still need some information to confirm:

    1. Could you remove FB15 and schottky with 0 ohm, and post a oscilloscope image with Vin, SW and Vout on one screenshot?

    2. What's you test load condition and have you tried to test with lower load? In your schematic, the output is 500mA. But for this boost device, we limit input current to 500mA so there might be some overload situation.

    Another suggestion, your layout of input and output ground can be connected with one wide copper. For high frequency layout, if the layout is not carefully done, the regulator could show stability problems as well as EMI problems. Please refer to our layout guideline in datasheet.

  • Dear,

    -->I already replaced the Diode with FB so that solves the problem but as datasheet mentioned i just want to verify where i am wrong.

    -->What's you test load condition and have you tried to test with lower load? In your schematic, the output is 500mA. But for this boost device, we limit input current to 500mA so there might be some overload situation.

    Ans : That is just for indication that This IC can provide 500 mA output,Actual current consumption is around 30 mA.So i dont think that would affect the functionality.

    Please have a look at the graphs...!!

    Vout Graph :

    Vin Graph :

    Vin = 3.8V

    SW Graph :

    Layout Image :

  • Hi,

    It's an abnormal phenomenon and we still need more information to figure out. I'm confused with the image you post, could you clarify your test condition like is FB15 and Schottky is replaced with 0 ohm? And could you capture a screenshot with Vin, SW and Vout on one screenshot, and use shorter time scale to see more details? Thanks. 

  • Dear,

    -->I'm confused with the image you post, could you clarify your test condition like is FB15 and Schottky is replaced with 0 ohm? 

    Yes,Its replaced with 0 ohm..!!

    -->I will provide you the screenshot ASAP...!!

    Thank you ..!!

     

  • Hi Tirthal,

    the possition of the output capacitor is not correct. there must be a output capacitor  between VOUT pin and GND pin.  please refer to page17 of the datasheet. 

    please change the possition of the output in current PCB and check again. thanks

  • Ok will look after that ,we are having no problem without schottkey. So in future will lookout for that.