Did the USB ESD issue damage my ESP32C3 module? - Page 1
Forum section: electronics / beginners

author: zzdwcm
author_rank: Newbie
timestamp: July 05, 2025, 07:57:18 am
content: Hello everyone,I'm experiencing a recurring issue with ESP32-C3 modules on my newly designed PCB, where three modules have already been damaged.Initially, the circuit powered on correctly: the ESP32 functioned as expected, with USB serial logs active and Bluetooth operational. However, over the next few days, various issues began to appear, including boot failures, anomalous GPIO behavior, and non-functional USB serial communication. Ultimately, each affected ESP32-C3 module became completely non-functional.I suspect the problem lies within the power supply circuitry. I'm powering the ESP32-C3 from the USB 5V VBUS line via an LDO, which outputs 3.3V.Almost every time I plug the USB cable into my MacBook Pro's USB port, I observe approximately 30-50V peak-to-peak oscillations on both the 5V (yellow trace) and 3.3V (blue trace) power rails.As there's already a TVS diode on the VBUS line, I attempted to verify its effectiveness. I placed a 1.8Ω resistor in series with the VBUS line and measured the voltage drop across it.The maximum voltage measured across this resistor was 20V, indicating a peak current of Imax = 20V / 1.8Ω = 11A.So there are some my questions:1) Given that static discharge (ESD) can easily exceed 1kV, is the observed 30-50V peak oscillation on the VBUS line an indication that my TVS diode is successfully clamping the voltage? Or is this 30V itself problematic?2) If the TVS diode did function correctly, why did such a high peak current (11A) flow through the resistor? I'm concerned this current also passed through the LDO and ultimately reached the sensitive ESP32-C3 chip.3) Could these 30-50V voltage oscillations be damaging my ESP32-C3 chip? The ESP32-C3 datasheet states that the chip passes 1000V CDM (Charged Device Model) ESD testing. Does that mean a 50V voltage oscillation is OK?4) What are the recommended next steps for mitigating these severe transients? Should I consider adding a 3.3V TVS diode on the LDO output?Any insights or suggestions would be highly appreciated!

author: tooki
author_rank: Super Contributor
timestamp: July 05, 2025, 09:33:46 pm
content: I’m not sure this is ESD; one possibility is that it’s actually inductive kick, caused by the cable inductance and ceramic input caps on the load and ceramic output caps on the supply; these cause an enormous inrush current, and then the sudden stop of current flow when the caps fill causes inductive kick. Can you test what happens if you replace the two 10 μF caps with two 4.7 μF (or one two 10 μF) electrolytic caps? (2 x 4.7 μF because the USB standard says loads should have a maximum 10 μF input capacitance, if I remember correctly.)

author: zzdwcm
author_rank: Newbie
timestamp: July 06, 2025, 12:27:33 pm
content: Thanks for your suggestion. But today I found that without the ESP32 PCB, directly connect scope to VCC/D+/D- pins of USB cable, and plug cable in laptop USB port, there is also such discharge pulse on scope. The waveform is the same as before. It happens about 7~8 times out of 10 tries on my macbook pro, and it is about 2/10 ~ 3/10 on my thinkpad laptop. And on thinkpad laptop, the p-p value is about 10~13V, much less than the value 30~50V on macbook pro.So, is it a ESD or something else? Is it a circuit issue of Macbook Pro, although there is the same thing on thinkpad.

author: tooki
author_rank: Super Contributor
timestamp: July 06, 2025, 02:07:08 pm
content: Quote from: zzdwcm on July 06, 2025, 12:27:33 pmDoes it happen if the laptop is running off battery (no power adapter connected)?Quote from: zzdwcm on July 06, 2025, 12:27:33 pmAsking the question again, without answering the question I asked, still won’t get you an answer. Your board has input capacitance too, even without the ESP32 board. So the test I asked you to do with electrolytic caps is still relevant.The difference between computers could be down to a few things. But please answer the questions. Without the answers, all we can give is speculation.

author: zzdwcm
author_rank: Newbie
timestamp: July 07, 2025, 05:59:49 pm
content: Quote from: tooki on July 06, 2025, 02:07:08 pmYes, it happens on both battery and power adapter.Quote from: tooki on July 06, 2025, 02:07:08 pmtoday i replaced these caps with 10uF electrolytic caps. Since it was a surface-mount resistor, I had to keep the electrolytic capacitor's leads relatively long for easier soldering. The test result is the same, the glitch on V3.3 and Vbus is about 20+V.And I also found another interesting thing: I try to use a USB hub to isolate the ESP32C3 and my macbook. There is a power switch button for each USB port on the hub. Even when the switch is off and ESP32C3 is not power on, the plugging USB hub's cable to my macbook still cause these spikes on V3.3 rail.

author: PlainName
author_rank: Super Contributor
timestamp: July 07, 2025, 08:46:58 pm
content: Can you separate the shield from ground? Connect the two via resistor or resistor/cap in parallel (100K/100nF).

author: JustMeHere
author_rank: Frequent Contributor
timestamp: July 07, 2025, 10:55:42 pm
content: Any chance you have your probe in 1x mode and your scope thinking they are in 10x?Also, what are you driving downstream of your LDO? With the ESP32, you are at your current limit and could easily be going over the 600 mA absolute max. The datasheet for your ESP module says needs a min current of 500 mA.How much capacitor do you have on your voltage input pins of your ESP32?

author: tooki
author_rank: Super Contributor
timestamp: July 08, 2025, 04:01:46 pm
content: Quote from: zzdwcm on July 07, 2025, 05:59:49 pmThanks.One more test: do you have a phone charger you could use as a power supply instead of a computer? If so, how does it behave if you connect the USB cablebeforeplugging the charger into the AC outlet? Does the spike happen when you plug it into mains?

author: zzdwcm
author_rank: Newbie
timestamp: July 09, 2025, 05:35:23 am
content: The shield and GND are directly connected with PCB traces。 But before I used a USB power cable which has no shield, and only VCC and GND lines. With this cable, there was still spikes occured.

author: zzdwcm
author_rank: Newbie
timestamp: July 09, 2025, 05:40:38 am
content: Yes, with 1x and 10x probes, testing result are the same.I also removed the ESP32C3 module and there was only power supply circuit on the board. But spikes were still there.

author: zzdwcm
author_rank: Newbie
timestamp: July 09, 2025, 05:50:00 am
content: I am not sure whether a tested case is the one you just said. I plugged a phone charger on the AC outlet, then plugged the USB cable connected to ESP32C3 to this phone charger. In such case, there was no spikes. I tried about 10+ times, the result always was OK.

author: Chalcogenide
author_rank: Regular Contributor
timestamp: July 09, 2025, 06:45:18 am
content: Have you tried with the Macbook running on battery power? It might be that the oscilloscope is grounding your ESP board, and the Macbook PSU has no ground, so you are suddenly discharging the Y-class EMI capacitors on the PSU into ground through your board and oscilloscope.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: July 09, 2025, 05:44:52 pm
content: Quote from: zzdwcm on July 09, 2025, 05:50:00 amThese are usually isolated. Easy to confirm by doing a continuity test between the ground on the USB wire and the AC plug blades.

author: Manul
author_rank: Super Contributor
timestamp: July 09, 2025, 08:38:19 pm
content: Is that 10ns per div? For such fast transients layout and low parasitic inductance is critical. TVS diode should be well placed, with as small ESL as possible, otherwise it will not clamp well. Capacitors too. A way to reduce inrush and/or ringing is a small series resistor or electrolytic capacitor. Unidirectional TVS diode might be a more logical choice. Note that such a short transient might also be a probing error (coming from long probe ground lead).