RAK3172 ESD Protection

[smilexs4 (Laszlo Benedek)]

I’m working on a design with the RAK3172 for an industrial device and reviewing the official documentation. I noticed in the RAK3172-SiP Application Note it states:

“If used in a harsh ESD environment, the following example is a reference design for ESD protection. The recommended part is Semtech - Rclamp2451z (1-Line, 24 V).”

This brought up a few questions for my design, and I’d appreciate some clarification:

1. On-Module Protection: Does the standard RAK3172-8-SM-I module include ESD protection on its RF pin?

2. ESD Rating: What is the ESD voltage rating for the RAK3172-8-SM-I module’s antenna input without any external protection?

3. Custom Design: I am also planning a design using the RAK3172-8-SM-NI (the no-connector version) for a custom PCB. Based on the app note, should I plan to include the Rclamp2451z (or a similar TVS diode) on my antenna trace to pass IEC 61000-4-2 Level 4?

Thank you for your help!

[carlrowan]

Hi @smilexs4 ,

1. There is no external ESD protection on the internals of RAK3172 going to the STM32WL chip.

2. Since no external ESD protection, we can based the ESD performance from the STM32WL documentation.

3. Adding Rclamp2451z TVS will generally help but still a matter of testing since it can still be affected by layout, ground, etc. Nevertheless, I’ve look on that TVS datasheet and it is designed for Level 4.

[smilexs4 (Laszlo Benedek)]

Thank you @carlrowan. I’ll add an external TVS diode to my own design.