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impedance configuration for ADG3304 Level translator

Question asked by marco55 on Jun 15, 2012
Latest reply on Jul 16, 2012 by mauri1106

I'm using the ADG3304 to translate the level of four input signals from 5V to 3.3V, but I have some problems.

The configuration is as follows:

I interface the input signals with HCPL-063A optocouplers. The output signals from this optocouplers have 1K pull-up resistors to 5V.

Then the signals are connectet to the Y pins of ADG3304 (the Vccy and EN are connected to 5V, while the Vcca is at 3.3V; also I have 100nF capacitor between Vccy and ground). Then the outputs of ADG3304 are connected to GPIOs of a BF518 dsp. (see attached image)

Between the HCPL-063A and the ADG3304 I had 1K resistors, but the signals that arrived at the DSP was always neither high nor low (a broad signal about 1.5V).

Now I removed those resistors but the signals at the DSP are always like this.

 

I'm not skilled in electronics, I hope someone can help me to better understand how to correctly configure this connection.

 

Thank you

 

Marco

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