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LM61495: How to identify fixed versions for 5V and 3V3

Sven Seitola
Prodigy 50 points
Part Number: LM61495

Hello,

I'm using the LM61495 for the first time in a design and I'm running into problems. I have a 100k / 24k9 feedback resistor divider to set the output to 5V. However, the output rises much above the 5V (until the current limiting of the lab supply kicks in). The output follows the input voltage with a little drop of some 300mV. I verified that the resistor divider is actually 100k / 24k9.

Now I wonder if I don't have one of those fixed version installed by mistake. Then the FB voltage is to be connected directly to the output rail without resistor divider. That would explain why the output rises above the set voltage.

The datasheet doesn't seem to tell about the part numbers or package markings of the fixed-version devices. How can I identify those?

Thank you!

  • 0
    TI__Guru 50120 points

    Hi,

    Please refer to section 5 "Device Comparison Table" to get a better understanding of which device is fixed or adjustable.

    Example (LM61495QRPHRQ1 = Adjustable , LM61495Q3RPHRQ1 = 3.3V fixed, and so on per table details).

    Can you verify what OPN you have for the LM61495? This can be found on your cutout-reel package information.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    Prodigy 50 points

    Sorry I don't get it. The table in chapter 5 lists only the different version for output current. 

  • 0 in reply to Sven Seitola
    Prodigy 50 points

    I'm back in the lab and can read the device marking. It is:

    1495Q3
    TI   12J
    P715G3

    So I actually have an automotive device installed, which was not intended (I specified LM61495RPHR). So far I checked only the datasheet of the non-automotive device, which might need an update about the fixed versions. Chapter 5 of the -Q1 datasheet does indeed list the fixed versions, and the chapter Packaging Information says that 1495Q3 is a 3V3 fixed voltage device.

    I will mark this as solved.

    best regards,

    Sven

  • 0 in reply to Jimmy Hua
    Prodigy 50 points

    Can I adjust a 3V3 version as well? Say I connect the output voltage via 100k / 51k resistor divider, will it be able to set the output to 5V? Or is there additional circuitry in the device that prevents that?

  • +1 in reply to Sven Seitola
    TI__Guru 50120 points

    Hi Sven,

    There are internal circuits that set the trims to get output fixed to 3.3V.

    I would suggest getting a 5V fixed variant or the adjustable variant if you want to different output voltages.

    Regards,

    Jimmy