3.6 volt trigger signal too high?

Embedded Security ChipWhisperer Hardware
1

I have a 5V target circuit and I use a 74LVC1G07 (Single driver with open collector output) to regulate down the signal I intend to use as a trigger. I use a pull-up resistor to the 3.3V coming from the target’s USB chip. When measured, it isn’t 3.3V but 3.6V. It would be smarter to connect the pull up resistor to the 3.3V coming from the ChipWhisperer Lite, but…

I believe ChipWhisperer Lite will tolerate 3.6V and even very close to 4.0V. What do your say?

e

BTW: Are the 5V pins connected to anything at all?

2

Hi,

The spartan 6 max IO pin voltage varies a bit by chip grade (not sure what’s on the Lite off the top of my head), but they’re all >3.95V, so you should be fine with 3.6V.

If you’re referring to the 5V pin on the 20-pin connector, this pin is disconnected on the Lite. It’s only connected on the CWPro.

Alex

3

Let me ask you before I send my Gerber files to China:
How would you do a level translation of a 5V trigger signal to 3.3V?
Would you use a voltage divider (e.g. 2K2 + 3K3 resistors)?
Would you use an active circuit? Like what?

e

4

Yeah a voltage divider should be fine