Verdin AM62 – USB_1_VBUS input impedance and detection with USB-PD (5–20 V)

Technical Support
1

Hi,

I am designing a carrier board for the Verdin AM62 and have a question about the USB_1_VBUS pin.

In my design the USB-C port uses a CYPD3177 USB-PD controller. The PD controller does not provide a dedicated attach/VBUS detect signal, so the only available point to detect VBUS is after the PD power path FETs. At this point the voltage can range from 5 V up to 20 V, depending on the negotiated PD profile.

According to the Verdin AM62 datasheet, USB_1_VBUS is used for VBUS detection and is 5 V tolerant, and it also mentions a voltage divider on the module.

To design a reliable external detection circuit I would like to clarify a few things:

  • What is the input impedance or input leakage current of the USB_1_VBUS pin on the Verdin AM62 module?
  • Is it acceptable to feed the pin through an external resistor divider (scaling 5–20 V down to ≤5 V)?

Thank you

2

Hi, I’m the Toradex AI Assistant.

I might make mistakes or occasionally get you wrong. Our support team will step in if needed.

I’d be glad to help with your USB-PD design! To provide accurate guidance for your carrier board design with the CYPD3177 USB-PD controller, could you specify which version of Torizon OS or BSP you’ll be running on the Verdin AM62?

For hardware specifications and design details, you can use the tdx-info command on your device to get detailed system information. You can find more about this tool at: Getting Device Information with Tdx-Info | Toradex Developer Center

The available documentation shows that the USB_1_VBUS pin is indeed used for VBUS detection and mentions a voltage divider on the module (1). However, the specific input impedance values and detailed electrical characteristics for the USB_1_VBUS pin that would be crucial for your external resistor divider calculations aren’t detailed in the current sources.

Common platforms to consider:

  • Hardware: Verdin AM62 (Solo, Dual, or Quad variants)
  • OS: Torizon OS 6, Torizon OS 7.2.0, BSP 6, BSP 7, Yocto 7.2.0
  • Integration: Device tree configuration, USB-PD implementation

Once you confirm your specific setup, I can provide more targeted guidance for your USB-C power delivery implementation with voltage scaling from 5-20V.

Best regards, Toradex AI Assistant.

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3

Hello @samuel.lehner,

I will discuss this topic with one of my colleagues and get back to you with more information.

Best Regards,
Bruno

4

Hello @samuel.lehner,

With such a wide input voltage, a solution with a voltage divider would not be adequate.
Our recommendation would be to implement a Comparator / Level Detector for anything above ~4.5 V.
This way you could detect up to 20V and still provide a value within 5 V to USB_1_VBUS.

Best Regards,
Bruno

5

Hi Bruno,

I would like to reduce the number of components, so I am looking for a simpler solution. I am considering a series resistor with a zener diode. For the design, I need the input impedance of this pin.

Thank you for your help.

6

Hello @samuel.lehner,

With a zener diode the solution should be viable.

The impedance to GND of SODIMM_159 is 30K.
We use:

  • Between SODIMM_159 and USB0_VBUS (SoC):
    • 2x 10K (1%) in series
  • Between USB0_VBUS (SoC) and GND:
    • 1x 10K (1%)

Best Regards,
Bruno

7

Perfect, thank you.

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