ESP32S3 inbuilt jtag pin protection

MattWork
Posts: 2
Joined: Tue Oct 01, 2024 6:05 am

ESP32S3 inbuilt jtag pin protection

Postby MattWork » Tue Oct 01, 2024 6:17 am

Hello,

TLDR: As the USB D+ and D- will back drive into the ESP32S3 will it damage it when ESP32S3 is not powered on?

I'm in the process of designing a PCB using the ESP32-S3-WROOM-1 module. Now i want to power the board via a 12V SLA battery. The board has the necessary circuitry to step down the voltage to 3.3 volts that the ESP32S3 wants.
My issue is if I use the onboard USB to JTAG debugger (GPIO19 and GPIO20) while the battery is disconnected will it damage the ESP32S3? I say this because the ESP32S3 wont be powered by its 3V3 pin when the battery is disconnected
As my USB will not power the board only D+ D- and Ground will be connected via USB to the board.

I've been going over all the data sheets including the WROOM datasheet, ESP32S3 datasheet and ESP32S3 technical datasheet and haven't found any information on pin protection, such as back drive protection.



Thanks,
Matt

ESP_Sprite
Posts: 9749
Joined: Thu Nov 26, 2015 4:08 am

Re: ESP32S3 inbuilt jtag pin protection

Postby ESP_Sprite » Tue Oct 01, 2024 2:52 pm

Hm, these things aren't really specced (but USB specs give an impedance of 28 ohm min, meaning worst case you'd have 100mA flowing into the pin, which feels like it should not be a problem) but why not simply allow your device to be fed from the 5V USB power supply as well?

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