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Old 1st March 2012, 04:31 PM   #1
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Question TDA8947 amplifier microcontroller

Hi, i'm trying to make a simple amp for my tv and i have 2 TDA8947J IC's from an old home-cinema. It's a simple circuit but i dont know what to do with the "microcontroller" that say's on the datasheet in the "Fig. 12" circuit, can anyone help me about this?

Thanks in advance,
John


PS. the datasheet is this
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Old 2nd March 2012, 07:51 PM   #2
fooboo is offline fooboo  United Kingdom
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Hello there

For Microcontroller read 'Any circuit that can be used to control the mute function. This could be a real switch between the point marked 'micro-controller' and VCC. Or even an LM555 Time delay circuit pin 3 of which would be connected to the point 'microcontroller' that would hold the mute on whilst the main circuit settled before turning the mute off and allowing audio to be heard.

Just under Fig 12. Read LOW as being -VE and HIGH as being +VE. This is where the 555 is usefull as it can be in either of these states at Pin3 when configured correctly.

regards

Foo
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Last edited by fooboo; 2nd March 2012 at 07:56 PM.
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Old 2nd March 2012, 09:00 PM   #3
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thank you for the reply.. i've already tried to connect the microcontroller point with the VCC but didn't work...if its not trouble could you send me a schematic with the 555 connected with the circuit in fig.12 or something else that could help me?
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Old 2nd March 2012, 09:18 PM   #4
fooboo is offline fooboo  United Kingdom
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Take it to -VE (GND) This is the LOW setting and turns the mute off therefore the audio on. I don't think you can leave the point 'floating'. IE it must be tied LOW to listen or HIGH to mute. Not left unconnected at any time.

I'll dig out a schem and post tomorrow.

regards

Foo
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Old 3rd March 2012, 04:16 PM   #5
fooboo is offline fooboo  United Kingdom
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This should do the trick [CN1] should go to the point marked [Microcontroller].

It starts with the output HIGH and after a delay, determined by the variable resistor and C1, the output goes LOW.

With the values shown the longest delay is around 5 seconds. Make C1 larger to increase the possible delay time and adjust VR1 to select your required delay within the range.

regards

Foo
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