Protecting the input pins

Hardware questions and issues with the FV-1

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studionebula
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Joined: Mon Nov 10, 2008 10:04 am

Protecting the input pins

Post by studionebula »

The data sheet for the FV-1 says "Although the FV-1 is fully digital internally, it has been designed with internal power supply bypassing and careful attention to signal pin protection devices so that only a clean power supply and expected analog techniques are required at the PCB level." But the data sheet also says, under Absolute Maximum Ratings, "Analog input voltage range -0.5 AVDD+0.5 V". So, does that mean that I need to protect the input pins from voltages outside this range, or not? Obviously I can use a couple of diodes to protect them, but if there is already a protection circuit in there then it would be redundant to do so.

Thanks--
--Adam
frank
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Post by frank »

Yes, you should protect the inputs from voltages outside the operating range (typically 0 - 3.3V) as the internal protection it really designed for transient protection, not continuously bleeding excess power to the rails as that will damage the chip. This is true for any chip, they all have some protection devices at the pins but they are not designed for running past their operating range continuously.
Frank Thomson
Experimental Noize
studionebula
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Joined: Mon Nov 10, 2008 10:04 am

Post by studionebula »

Thanks, Frank. The project I'm working on is putting an FV-1 into a modular synthesizer, where it can potentially be exposed to voltages as high as +/-15V, so I'll definitely put in protection diodes as well as scaling the voltages.

--Adam
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