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KA , 03-07-2025, 03:43 PM

Hi everyone!

I have a question about the ESD7104 component (datasheet: [onsemi](https://www.onsemi.com/pdf/datasheet/esd7104-d.pdf).

Websites like Mouser list it as:
Description: ESD Protection Diodes / TVS Diodes **BI-DIRECTIONAL**
Polarity: **Unidirectional**

I’m a bit confused—what does unidirectional polarity mean in this context? Does this imply that signals flow specifically from pin 1 to pin 10 and not vice versa? Also, I'm having trouble interpreting the diagram in the datasheet.

Would appreciate any insights! Thanks.

QDrives , 03-07-2025, 05:15 PM

First of all, Digikey is not the manufacturer. If you look at the screenshot from them, you can see they have a mistake. Either all 3 should be bi-drectional or uni-directional.
Now for the other problem -- OnSemi does not mention either uni-directional nor bi-directional. So Digikey needs to 'create' this on their own.

If you ask me, I would say this is a bi-directional TVS diode array.

As for some of your other remarks:
- Pins 10, 9, 7 and 6 are NC, as in Not Connected. This allows you to route traces through -- so a trace coming in at pin 1 route to pin 10 and continue to your IC.
- Uni-directional means voltage is limited from -0.6V ... +5V. Bi-directional would be -5V ... +5V.
However, the 2 diodes in series, that is in parallel to the zener diode, makes this non standard.

KA , 03-07-2025, 05:36 PM

@QDrives Thanks for the detailed response.

Just to clarify - Are pin 1 and 10 internally connected or do I need to externally connect them using traces?

Also are there alternatives that you would recommend that use standard design?

QDrives , 03-07-2025, 08:47 PM

No pin 1 and 10 are not internally connected. Pin 10 is **NC** Not Connected.
It is up to you to decide **if** you want to route through pin 10 or not. If so, then you have to place a trace.
What do you mean with "standard design"?

For 'alternatives' https://www.digikey.nl/en/products/filter/transient-voltage-suppressors-tvs/tvs-diodes/144?s=N4IgjCBcoKwGxyqAxlAZgQwDYGcCmANCAPZQDaIA7JWJQBwAsIRAnDAAyJFgPvsBMzcGHYw6QhnRgwGEbvwDM-FkLCKF7VRoYKtHFdwUt%2BlVZRaSzbXd0knVMMPAcxFDqXJBxK-OudVwDJQwQnQKCmKC3N4s4tw0YWbSceD0wUL8YHTKEnCOCimZYUzcsWBcIPwCcAaVAjQZouyFHHkZBXS1HOwWFb6ufVL2RCbhpkQKalJCk74ps3SIALpEAA4ALlAgAMrrAE4AlgB2AOYgAL5ElHAQ0CCokJi4hCTklQwstJ78H1m6KyANltdodThciABaQR3B77ACuL1IkAoXRAS0uIAhuhhUHhiLeIjRGIhKhxkDxRCRFAg6PO5yAA

KA , 03-08-2025, 03:11 AM

@QDrives Thanks.

You had mentioned - "the 2 diodes in series and in parallel to the zener diode makes it a non-standard". Hence, I was wondering if there is any standard design for TVS diode arrays.

I had worked with 0402 TVS diodes earlier. The ESD7104 was something that I used for the first time and overlooked the NC pins, assuming that they would be internally connected. This goof-up resulted in my prototype boards not working.

QDrives , 03-08-2025, 07:54 PM

"*Hence, I was wondering if there is any standard design for TVS diode arrays.*" -- Not really. Besides, it is what the manufacturer presents. This can be simplified or more accurate.