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LM1875: LM1875T/LF05

Haiqiang Zhu
Prodigy 90 points
Part Number: LM1875

Hi

What is the difference between different LM1875T part, for example LF02/LF03/LF05/LB05? I didn't find the difference in the datasheet.

BTW, the mark on the chip is "85ACT5UG3" "LM1875T", can you help to confirm if it is LF05? Thanks.

  • 0
    Prodigy 90 points
    Hi
    Would you pls help to check this issue? Thanks.
  • 0
    Prodigy 90 points
    Hi
    Can you help to check this issue? Thanks.
  • 0 in reply to Haiqiang Zhu
    TI__Genius 9995 points

    Hi Haiqiang,

    Sorry for the delay as it is an old device needing time to figure out the difference.

    On my side, table below and older version of datasheet can explain the details. But as to what type of LM1875 in your hand, please see pin description for the confirmation.

    LM1875 datasheet NS version.pdf

    Regards,

    Alix Wan.

  • 0 in reply to Alix Wan
    Prodigy 90 points

    Hi, Alix

    Thanks for your feedback. I didn't find suffix of LF05 in the old datasheet. So you mean that with different suffix that only means different pin format and should be electrically the same?

    The problem we current have is that with different lot on the same PCBA the behavior will be different:

    1. with mark 55AETDUG3: the quiescent current 38mA, no oscillation at output

    2. with mark 85ACT5UG3: when no load connected, the quiescent current about 60mA, about 4.24V@2MHz oscillation at output, when speaker connected, the oscillation is gone, and the quiescent current drops to 11mA.

    If I connect a 375ohm to the output or connect a 3.3ohm resistor series with 0.47uF capacitor, the oscillation can also be removed.

    For both parts, the function is ok when speaker is connected and the gain is correct as set.

    Do you have any comments about this? Thanks.

  • 0 in reply to Haiqiang Zhu
    Prodigy 90 points
    Hi,Alix
    BTW, do you know that LM1875 differs by version that shows on the chip mark at the left bottom circle, we found there will be "V2", "V3" and "V5", V2 and V3 behave the same(no oscillation without load and higher current with load) but V5 behaves different(oscillation without load and lower current with load). Thanks.
  • 0 in reply to Haiqiang Zhu
    TI__Genius 9995 points
    Hi Haiqiang,

    Sorry for the delay.
    Can you upload the pictures of mask of these chips to me? As this is a quite old part form NS, I need something specific to look into this.
    In addition, i do not think function of these devices varies. But anyway, can you scope the pictures to show me the difference?

    By the way, how do you buy these amplifers? I will loop more colleague to help to look into it.

    Regards,
    Alix Wan.
  • 0 in reply to Alix Wan
    Prodigy 90 points

    Hi, Alix

    Pls check the following pictures for the mark. Mark1 has oscillation issue when no load, and mark2 didn't have oscillation issue.