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STM32F439 - Undershoot on FMC pins

Question asked by az.E on Apr 19, 2016
Latest reply on May 2, 2016 by AvaTar
Hello, 
We are using the STM32F439 in our application.
While using the simulation with IBIS model (Hyperlynx), we have discovered undershoots on FMC pins.
The voltage in undershoot is about -866mV and the current limit is about -11mA.
The duration of the undershoot is 2nSec and repeatable every 50nSec.
From the Data Sheet of the STM32F439, we understand that the voltage on FMC pins not allowed to fall below -0.3V, and if the voltage is lower than the -0.3V, the current has to be limit to -5mA.
Our questions -
1. Is the requirement in the Data Sheet of maximum current of -5mA dependent on the duration of the undershoot? (for example, for short duration the maximum current allowed is higher)
2. Is an undershoot of -866mV with maximum current of -11mA for 2nSec every 50nSec on FMS pins can cause a damage to the ST32?
Thank you, 
Waiting for your answer,
Itai.

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