isd1760 problem

Discussion in 'The Projects Forum' started by a21, Apr 6, 2010.

  1. a21

    Thread Starter New Member

    Mar 24, 2010
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    0
    Hi,
    I tried to realize the stand alone circuit in the datasheet of ISD1760 with the buttons and ANAIN. The problem is that when I tried to play what I recorded it "plays" only noise and buzzing. The only difference is that I don't put 0.1uF capacitors, because I haven't got at home.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Without so much as a glance at the datasheet, I can tell you that the capacitors are REQUIRED for proper operation.

    If you leave them out, all you will get is noise and problems.

    If they were not required, they would not show them.

    As a general "rule of thumb", ALL integrated circuits require a minimum of a 0.1uF (100nF) "bypass" capacitor across their power/ground terminals. Some require more; one example is a 555 timer.

    If a single supply IC, you need at least one from ground to +V/Vcc/Vdd.
    If a dual supply IC, you need at least two; one from ground to +V/Vcc/Vdd, and another from ground to -V/Vee/Vss

    [eta]
    I presume this is the datasheet you're looking at: http://elexp.com/a_data/ISD1700.pdf

    Yes, you will only hear noise unless you use ALL of the recommended capacitors.
    I suggest that you use metalized poly film caps.
    Ceramics might work, but will have more noise than the poly.
     
    Last edited: Apr 6, 2010
  3. a21

    Thread Starter New Member

    Mar 24, 2010
    8
    0
    I found 1uF metalized poly film and 100nF ceramic capacitors. I will try it tonight.
     
  4. a21

    Thread Starter New Member

    Mar 24, 2010
    8
    0
    Ok, I tried and it happens. Thanks, SgtWookie. I thought that these capacitors are not important because I have a filter in the power supply, but obviously they are :)
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I am glad that you got it working. :)

    You have also learned a very valuable lesson; in that capacitors are not something that can be omitted.

    In many schematics that you will see over the coming years, you will notice that very often capacitors across the supply/ground lines (bypass caps) are not shown by ICs, just to keep the schematic less "cluttered". It is simply understood that capacitors are required for proper operation.

    If you forget this fact, it will "bite" you - every time. :eek:
     
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