LM3410: LM3410

Hi Irwin ,

Thanks for your reply.

I output voltage required is 22.4V and the Iout required is 40mA.

With regards,

Jayashree.

Hi Irwin,

The selected parts are fine right.

Let me know for any other updates required.

Is schematics is proper?

With regards,

Jayashree.

Hi,

I have updated D52 part to DFLZ30-TP, check whether it is suitable.

With regards,

Jayashree.

Hello,

If your output is 22.4V and the abs max of the SW node is 26.5V you will not be able to protect for an open LED string this way.  The datasheet of the DFLZ30-TP does not have enough information to know when it will start pulling up on the FB node.  It has a +/-6.7% tolerance at 25 mA, 28V to 32V.  This doesn't include the knee of the zener voltage versus current.  when it starts conducting it will start feeding curretn to FB lowering the LED string current.  At 22.4V output this method will not work.  What is the tolerance of the LED string voltage?  Does it have to operate at cold temperatures, if so what is the string voltage at the coldest operating point?  What is the tolerance of the LED Vf?

22.4V + D51 voltage is approximately 22.8V.  That leaves 2.8V to hit absmax.

Best Regards,

Hi,

Could you please suggest me the diode part that to be used in the design.

With regards,

Jayashree.

Hi,

I am attaching the LCD  datasheet that I am using in my design for your reference I think this may help you in guiding me.

With regards,

Jayashree.FT055FHD-P01,RevA;191120.pdf

Hello,

The maximum voltage of the LED is 23.8V at 25 degrees Celsius.  If you plan on running this at lower temperatures the LED forward voltage is not mentioned and most likely will go up.  This is at 40 mA per the datasheet however there is a graph, on page 12, showing maximum current that only goes to 25 mA and needs to be reduced at higher temperatures.  This LED voltage leaves no room for over voltage protection, which isn't necessary if the output is never opened.  For colder temperatures you would either need to get information from the manufacturer or test this by measuring the LED voltage at 25 Celsius when first turned on and again at your coldest operating point right when turning on.  If the voltage is higher when it is cold take the different between the two numbers and add it to 23.8V.  The recommended operating range maximum for the LM3410 is 24V, Abs max is 25.6V and you have to subtract the boost diode forward voltage.  This leaves little margin.  Note you have to add the current sense voltage to the 23.8V as well making this 24V plus the increase at cold temperatures if it needs to run at colder temperatures.  We have other boost converters that can run higher voltage though they require more components.  TPS92691, TPS92692 as well as others.

Best Regards,

Hi,

Thanks for your input.

The operating temperature of the product is 0°C to 70°C.

Can I use the below mentioned part for this application?

There is only limited space in the PCB so I am trying to minimize the number of components. Please suggest me any other parts meeting my requirement with small package.