[sdiy] Protecting an input from overvoltage

[jhaible at debitel.net]

Schottky Diodes to VCC (+5V ? ) and GND (supply voltage of the ADC).
They will conduct before the chip's internal protection diodes will
be stressed.

JH.


> Hi,
> 
> I'm trying to work out the best (hi-fi) way to protect the input of a 
> CODEC chip from overvoltage.
> 
> The datasheet recommended input configuration is this:
> http://burnit.co.uk/sdiy/balanced_input_stage.gif
> 
> Basically AIN+/AIN- on the CODEC chip need to be kept >=0V and <=5V.  I 
> thought of a couple of solutions, but both seem to have drawbacks:
> 
> (a) Run the input opamps from power rails of 0V and 5V.
> Drawback:
> I want to be able to drive the CODEC near FSR (5.6V ptp AIN+ - AIN-) 
> even when running from an unbalanced source (i.e. the AIN- input 
> grounded).  My preferred opamp OP275 won't go anywhere near the power rails.
> Maybe there's another more suited opamp also with excellent audio 
> performance?
> 
> (b) Use 2 sets of series zener & signal diode to clip any overvoltage.
> Drawback:
> I'm not sure the diodes will be fast enough acting to protect the CODEC 
> input.
> I'm concerned the leakage current of the diodes will distort the normal 
> signal.
> 
> Any comments, other ideas?
> 
> Seb
> 
> 
> 
> 
> 




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