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LM3410-Q1: LM3410YMF/NOPB

Kavita Joshi
Prodigy 10 points
Part Number: LM3410-Q1
Other Parts Discussed in Thread: LM3410

Hi there, 

Till now I discussed my schematic and heat issue with William. 

I am seeking for solution to lessen the heat on board.

TI ic LM3410 and inductor 47uH is a heat producer, may be not sure, making my board hot.

Kindly resolve the problem asap.

Kavita

  • 0
    Prodigy 10 points

    This is the layout for your refence:

    This is my design I am working on:

  • 0 in reply to Kavita Joshi
    TI__Mastermind 28655 points

    Hello Kavita,

    What is the part number you are using for the LM3410?

    Is it the 'X' or 'Y' part? 

    What is the part number for the inductor being used? 

    With R8 at 1 ohm the current should be 190 mA. 

    What is your output voltage or overall LED stack voltage?

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Prodigy 10 points

    Hi Irwin,

    What is the part number you are using for the LM3410?

    LM3410YMF/NOPB

    Is it the 'X' or 'Y' part? 

    Y

    What is the part number for the inductor being used? 

    L0603B470KPWFT

    With R8 at 1 ohm the current should be 190 mA. 

    I can tell you voltage accross R8 and across R5:

    vtg across R8 = 10.35mV (R8 = 1 ohm)

    vtg across R5 = 21.96V (R5 = 0 ohm)

    What is your output voltage or overall LED stack voltage?

    vtg across R5 = 21.96V

    R5 is 0 ohm

  • 0 in reply to Kavita Joshi
    Prodigy 10 points

    Sorry! the part number is different:

    What is the part number for the inductor being used? 

    LPS6235-473MRB

    This inductor I have used now in circuit. 47uH/1.2A

  • 0 in reply to Kavita Joshi
    TI__Mastermind 28655 points

    Hello,

    I assume the voltage at the output is 21.96V not across R5 since it is zero ohms.

    I tried to find the information on the diode part number, D5 on the schematic, what is the exact part number?

    How are you looking at these voltages?  Are you using an oscilloscope?  At 21.96V you are getting close to the absmax of the device.  If the current is low it may exceed abs max when trying to provide full current to the LEDs.  You will need an oscilloscope to see this.

    Are you providing 3.3V to the input?  If so the inductor current will reach over 1.4A when providing 190 mA to the LEDs at 21.96V output, the inductor is a bit small for this.

    What are you driving?  Number of LEDs and if they are accessible?  I would try reducing the output voltage by lowering the LED stack voltage to see if it starts working.

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Prodigy 10 points

    Hi 

    I am measuring voltages with multimeter.

    Are you providing 3.3V to the input? 

    yes.

    What are you driving?  Number of LEDs and if they are accessible?

    I am using LCD display of 10inches. Part number: KWH101KQ14-C01

    Diode Part number : CMHSH5-2L TR

      You will need an oscilloscope to see this.

    Okay. I will observe the voltages with oscilloscope again.

    Let me know if you have any suggestion to do for me.

  • 0 in reply to Kavita Joshi
    Prodigy 10 points
    1.   Datasheet for LCD is attached here.
  • 0 in reply to Kavita Joshi
    TI__Mastermind 28655 points

    Hello Kavita,

    CMHSH5-2L is a 20V diode.  It needs to be a higher voltage rating than this.  30V should would be since the LM3410 isn't rated that high. (see below for additional information, the 20V diode may be fine is the output voltage is supposed to be 9.6V.)

    After looking at the display specifications the backlight should be 9.6V at 180 mA.  If you are seeing 21.96V something else is wrong.  Make sure the load is connected and R5 is really zero ohms.  If the load is open the LM3410 will, most likely be damaged though the CMHSH5-2L may be saving it due to it breaking down before the LM3410.  If the backlight voltage is 9.6V then the 20V diode should be okay.  Look at 8.1.1.7 on page 14 of the datasheet to how OVP is implemented as well as figure 14 on page 15.  Make sure the backlight is connected correct and there are no open paths on the board.

    Best Regards,