Other Parts Discussed in Thread: TPD2E2U06
Hello,
in a recent design I'm using the TPD2E001 to provide ESD protection to two LVC-devices connected to external BNC connectors, see here:
However, I figured that for the input signal ("IN") the TPD2E001 through path "A" provides current to the +5 V rail when the power supply is switched off.
With the power supply switched off and a 1kHz signal provided to the "IN" connector, the +5 V rail (green trace) looks like this:
This current leakage into power rail (with the ESD bypass capacitor C1 even smoothing the input signal considerably) prevented a different component (also connected to +5V rail) from triggering its power-on-reset when the power was turned on. Consequently this component failed due to improper initialization.
I fixed this by breaking the connection of the Vcc pin to +5 V rail (see arrow at "A" in schematic above). The TPD2E001 explicitly describes this kind of application. Furhter, I could not see any signal degradation so far.
Still I wonder what ramifications there are due to not using a Vcc connection. As TPD2E001's diodes are not biased by Vcc any more,
a) their parasitic capacitance might increase (as detailed here, p. 24). and
b) there might be a new path "B" for AC signals to ground.
Do I have to worry about them?
After the TPD2E001 gave me so much trouble, I am looking for a replacement device that needs no VCC connection. Would TPD2E2U06DRLR be a good choice? At least the datasheets recommends it.
Thanks.
Dan