I am working on incorporating ESD protection for flash circuitry on ESP32 custom PCB board, and after initial research, ordered an ESD Array (CM1293A-04SO) from digikey with datasheet here

Attached in the circuit diagram below, showing

  • USB Rx, Tx, and Pin 0 connecting to 3 channels of the array, and
  • Handmarked "Flash_3.3V" netlabel connecting to Channel 3,4 via Blue Line and connecting to IC Power Source at pin 5 via Red Line.

My questions is regarding the power line (2 options drawn in red and blue), and I am wondering if the array can simulataneously power and protect the incoming power from USB line.

Circuit Diagram

I got this idea from another protection array RClamp7522T with datasheet link here. with similar electrical circuit ( but higher pricing, with lower capacitance, higher protection range for ESD, a shared zener diode, and no power source), where it shows on page 7, that IC can protect power circuit as well. Please see screenshot

for page 5 here.

  • \$\begingroup\$ I came across the post mentioned below where someone said ESD pulse can be handled by the bypass capacitors which I have in place. I guess, I need to build the circuit and test it out myself. electronics.stackexchange.com/questions/401699/… \$\endgroup\$
    – Amogh Jain
    Commented Jan 2, 2021 at 0:20
  • 1
    \$\begingroup\$ Yes, either will protect. \$\endgroup\$
    – DKNguyen
    Commented Jan 2, 2021 at 2:46

1 Answer 1


So I learned and answered my original Questions after some R&D :

ESD protection is different for

  • Digital I/O Lines
  • Power Lines

Digital IO Lines :

  • as they are usually one way Industry preference if for high preference for unidirectional TVS
  • Additionally CMOS inputs are VERY sensitive to negative spikes, and unidirectional TVS have IV characteristic curves where cutoff/forward bias for negative spike is MUCH less than Positive spike
  • Power Dissipation Requirement is low, order of milliWatts

Power Lines :

  • Require Large Power Dissipiation (watts)
  • Industry practise is to use bidirectional TVS's

The above IC being used and tested, and even thoough working, WILL not provide rectification for power, as it is rated ONLY for ~250milliWatts.

Going to replace :-

  1. Digitial IO Protection with : Applied-Power-AU3321D5_C393856 @ LCSC $0.03
  2. Power Line Protection with : MMBZ5V6ALT1 @ Digikey (0.10), and LCSC @ $0.03 with 40Watts sinking capability.

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