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KL17 Hardware ADC Voltage Range and Injection Current

Question asked by Patrick Clapsaddle on Jun 21, 2018
Latest reply on Jun 25, 2018 by xiangjun.rong

I’m using the KL17 in a design, and am using the single ended ADC. I need clarity on a couple of things.   The datasheet (page 32) states input voltage should be a max of VREFH. My VDDA = 3.3V, my Vref = 3.0V.  Does this mean my voltage must be limited to 3.0V, or does the datasheet mean it can only read to 3.0V, but is ok to VDDA (or VDDA+0.3V)?

 

Also, I see in the datasheet that it is stated that no diode to VDD, and thus no positive injection current number provided.  I have signals running to the single ended ADC pins through an OP amp, with diode protection.  (stripped down image attached) If my input is floating, the diode clamps and holds the voltage to 3.63V.  Measuring across the 1.74k resistor, I calculate 5nA of current. Is this acceptable approach, or do I risk damaging the micro?

 

Thank you.

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