STM32 ADC protection diode

[jean_prieur]

Posted on September 18, 2013 at 11:58

Hello,

I want to protect my ADCs from overvoltage and ESD, and limiting the input to 3.3V.

This is my schematic:

There is a voltage divisor to convert 5V >  3.3V.  The top resistor is also used as the diode resistor.

There is a lot of special diodes in the market: TVS, zener... Do you know a part number which can fit for my application ?

Thanks !

[jpeacock2399]

Posted on September 18, 2013 at 15:54

I use the ST USBLC6-4 series TVS diode arrays.  They are intended for USB but work well as a low capacitance TVS diode.  The array clamps the input line to the power rails.   I like the USBLC6 since it has either 2 or 4 diodes for multiple channels plus a fast breakdown diode between ground and VDD. 

For single diodes and no line clamping I use the NXP PESD series TVS diodes for 5V and 3.3V lines.  For 24V outputs (common in industrial process control) I use the Vishay QSBT40 TVS diode array.

I also use zeners to clip the input voltage to an ADC channel in cases where the ADC VREF is below the VDD power rail.

  Jack Peacock

[emalund]

Posted on September 18, 2013 at 17:38

a Zener is too slow for transient suppression

Erik

[jean_prieur]

Posted on September 19, 2013 at 16:58

Thanks ! I also use the PESD5V0S1 for my resistive touchpad input. I think I will use it for my ADC inputs.