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UC3842AN vs UC3842BN

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  • UC3842AN vs UC3842BN

    Working on a Mackie SRM 450 V2.
    It uses a UC3842AN.
    I only have the BN TYPE. What are the differences between the two?

  • #2
    Totally interchangeable between the A and B versions...
    The difference was in the metal layers and bond wires..
    No performance differences... so go ahead and use the B version...
    Unitrode was the father for that part....
    TI had taken over Unitrode back around 1998-2000 ....
    TI did make a B version called a TL3842B...
    Personally this part should be dropped in the bottom of the ocean.. This part has caused lots of problems over the years ..
    Main problem is poor regulation with respect to temperature... The error amplifier rarely ever meets the data sheet min spec...for bandwidth and offset..
    Many times I did re-design with external op-amp ....
    Let me know If you need any further assistance...since I had direct involvement in the design of some of these controller ICs .....

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    • #3
      Originally posted by cerrem View Post
      Totally interchangeable between the A and B versions...
      The difference was in the metal layers and bond wires..
      No performance differences... so go ahead and use the B version...
      Unitrode was the father for that part....
      TI had taken over Unitrode back around 1998-2000 ....
      TI did make a B version called a TL3842B...
      Personally this part should be dropped in the bottom of the ocean.. This part has caused lots of problems over the years ..
      Main problem is poor regulation with respect to temperature... The error amplifier rarely ever meets the data sheet min spec...for bandwidth and offset..
      Many times I did re-design with external op-amp ....
      Let me know If you need any further assistance...since I had direct involvement in the design of some of these controller ICs .....
      Thank you for replying.
      I tested both in circuit. It seems like the free running frequency is a bit lower on the AN version. Go figure...

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      • #4
        Originally posted by diydidi View Post
        Thank you for replying.
        I tested both in circuit. It seems like the free running frequency is a bit lower on the AN version. Go figure...
        That's the crappy initial tolerance of that series of parts....
        The clocks are jittery, the error amp bandwidth are typicall 700kHz.. The EA input offsets are like 50mV..
        There is horrific ground bounce inside that IC .... The digital and analog grounds are on the same substrate with little to no protection guard bands....
        The 1 Amp drivers are too weak to properly drive any good low Rds-ON FETS....
        Keep in mind those chips were designed in the 80's and were made on a cheap substrate process...to maximize profit...
        Military did use those chips in the 90's and still today in some applications...but those versions are on a different process for space grade and screened..
        At one time Intersil made a Rad-Hard version of that chip...
        They did have the capability to make high quality ICs in the 80's...it would just cost too much...
        If Burr Brown made that chip...I bet it would would be like 50 ppm or better with a laser trimmed band-gap reference...

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