Please refer question 3. in this KBA: CX3 Hardware: Frequently Asked Questions - KBA91295
Question: How much current does CX3 draw from the USB VBUS supply?
Answer: The total current CX3 draws from the 5-V source in normal mode is approximately 112.6 mA. This is the worst-case scenario (1080p at 30fps, 24-bit data bus, 6 V at VBUS, 3.6 V for I/O supply, 1.25 V for Core / USB 3.0 supply).
Note: These values are based on the following criteria summarized in the table below. This assumes using switching regulators with approximately 85% efficiency for 5 V to 1.2 V, 1.8 V, or 3.3 V conversion.
External Power Converter Efficiency
Input Power (W)
Core 1.25 159.2 0.199 VBUS 6 22.6 0.136 U3Tx 1.25 17.1 0.021 U3Rx 1.25 30.2 0.038 I/O supply 3.6 23.5 0.085 Total power 0.478 0.85 0.563 Current from VBUS 5 112.6
If you use only the USB 2.0 port of CX3, then the current drawn is approximately 98.6 mA. When the device is in the standby mode, it draws approximately 68 uA; in the suspend mode, it draws approximately 3.2 mA.