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LMC568 replacement part

Jukka Kähkönen
Prodigy 10 points
Other Parts Discussed in Thread: LMC567

"Part number" I put this LMC568, but page does not regognize it. 

In our product we use LMC568. Look it is obsole, so need replacement part. We will make redesign, so pin-to-pin compatibility not need. 

Rt and Ct are 8530 ohm and 470 pF so oscillator freq is about 180 kHz. 

We use it Carrier detect output: it is connected to processor. 

Also we use it output pin 2. 

So, need similar circuit. So, about 90 kHz frequency (osc = 180, so freq = 180/2). Carrier detect output. Voice output. What is compatible or similar part?

  • 0
    TI__Guru 52090 points

    Hi Jukka

       I'm sorry, I didn't able to search out this device, seems the part number is not correct.

       If you need an audio amplifier, could you please follow below link to search for suitable device?

    https://www.ti.com/audio-ic/amplifiers/products.html

  • 0 in reply to Shadow He
    Prodigy 10 points

    https://www.mouser.com/datasheet/2/405/snas559b-284899.pdf

    Datasheet sitll available but obsole. So this is reason I ask this. "What is similar/replacement for new design"? 

    LMC567 is compatible partially: "Carrier detect" output found. But output pin 2, it is not in LMC567. 

    So: 

    - Need functional compatible part for new design

    OR

    - LMC567 is possible use for carrier detect. But need also any circuit for function pin 2, output signal. So maybe two part. 

  • 0 in reply to Jukka Kähkönen
    TI__Guru 52090 points

    Hi Jukka

       Seems the LMC567 is the best choice, I try to search for other devices, but sadly maybe we don't have other similar part.

       The pin1 in LMC567 could be used for output, could you please check if this part could suit your need. Thank you. 

  • 0
    Prodigy 10 points

    LMC567 maybe not right replacement for LMC568. 

    I read schematic and solution. It is old design and LMC568 must be replace with new one. 

    - Pin 8 use as "carrier detect": Calculate + measure tell carrier frequency. It is 80 kHz. I measure this from real-life-solution. 
    - Pin 2 is output. Look in this real life solution it is speech. So: It is two device, "transmitter" and "receiver". Inside receiver found this LMC568. Transmitter make 80 kHz carrier signal. Inside it is microphone + amplifier and transmitter modulate (FM) this 80 kHz carrier signal. 

    So: receiver use CARRIER_detected and demodulated signal. So. Receiver must be fm-demodulator. So... receiver it is as FM-radio but with wired communication and 80 kHz carrier. 

    I read LMC567 datasheet, and in my opion it does not make it.  It is not FM-demodulator. So I need any simple FM-demodulator. 

  • 0 in reply to Jukka Kähkönen
    TI__Genius 9260 points

    Hi Jukka,

    Let me check in our clocking portfolio that could replace this device.

    Best,

    Asim

  • 0 in reply to Asim Khan
    TI__Guru** 111070 points

    Hi Jukka,

    I am afraid we don't have other replacement option for LMC568. 

    LMC567 is the closet alternative we can provide. 

  • 0
    Prodigy 10 points

    LMC568 VERSUS LMC567 (LM567...). 

    Now I waste much time compare this two circuit. I read your answers and look you does not know LMC568 was TI product. I can say: Yes, it was, and not many years you stopped it. I can show you this secret: it really was TI circuit!

    But, LMC567 is active and LMC568 you can use google. 

    ADDITIONAL QUESTION IS: 

    Our solution is very easy. It is ancient audio communication system using Lo-Fi audio. (Lo-Fi- is opposite of HIFI). In our old system we use 82 kHz carrier frequency. Audio we transfer is speech, so, traditional "300 Hz...3kHz" is enough. 

    So, LMC568 was excelent. Solution is very, very, very simple: VCO frequency as must, 2x, carrier detect and fm-demodulated signal output. Carrier detect as pin 8, and fm-demodulated pin as pin 2. 

    Now I read LMC567 datasheet, and officially it says "tone decoder", and using google it is easy to find LM567 and LMC567 schemas how to use it several tone decoders. BUT. Internally and functionally LMC568 and LMC567 are similar. Pin 8 is just same, carrier detect. And pin 2 is just same, without any difference. 

    If we need somethn special, eg. many megaherz fm-demodulation, we can forget this. But, carrier is 82 kHz. 

    Is it any reason WHY it is not possible use LMC567 just as LMC568- fm-demodulator? Only a little differencies, in my opinion "cosmetic differencies". 

  • 0 in reply to Jukka Kähkönen
    TI__Guru** 111070 points

    Hi Jukka,

    Given this is a very old product, unfortunately, our team does not know this part. I agree that, from the datasheet, these devices look very similar and they look pin compatible. However, we are not able to locate any documents that describe these devices better than the datasheet.

    If you already have a board that is using LMC568, could you order some free LMC567 samples and do a drop-in replacement experiment?