Glitching lpc1343 : glitches don't go to 0V

Hello,

I am trying to glitch the lpc1343, I followed the tutorials:

Fault_6-LPC1114_Fuse_Bypass.ipynb
and https://toothless.co/blog/bootloader-bypass-part1/

My glitches are not going to 0V, the minus voltage that I get is 1.05V. Here is the form of the glitch:

But if I compare with a glitch that I did with the UFO board and STM32F3, I can go down 0.5V :

https://ibb.co/VtNyrng

Do you know why without the UFO board, my glitch don’t go under 1.05 V ? Maybe I am doing something wrong with the ground ?

I am using directly the pin 3 (+3.3V) as a voltage source, the pin 2 as a Ground ( from the 20-pin chip whisperer connector )

I am also using the jp11 glitch 3-pins using jumper wires (one on the ground and one on the glitch pin). My jp11 pin is connected directly to the VCC line ( from pin 3 of the CW ).

Thank you for your help.

It’s pretty normal for a glitch to not go to 0V due to inductance between the glitch MOSFET and Vcc, capacitance, the Rds on of the MOSFET, etc. You can pull Vcc to 0V if you keep the glitch on for a lot longer, but, in my experience, this has never been necessary. You usually end up crashing the target long before your glitch gets large enough to pull the circuit all the way to 0V.

Alex

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