The ultimate nightmare for hardware engineers is nothing more than a circuit board exploding during debugging, causing the computer to "die together"! To avoid this risk, I DIYed this high-speed isolated USB hub—with a 1500V isolation voltage, it can reliably isolate the chain reaction damage caused by circuit failures, building a solid safety barrier for the computer. Its transmission speed is close to 480Mbps (approximately 60MB/s), easily handling even high-throughput devices such as logic analyzers, and peripherals such as USB sound cards are no problem at all.

First, the essence of isolation is "disconnecting the electrical connection and only transmitting signals and energy":

(1) Data isolation: The differential signals (D+, D-) of USB 2.0 are transmitted through a high-speed digital isolator (supporting rates ≥480Mbps). The isolator internally achieves electrical isolation between the primary (upper-level) and secondary (lower-level) sides through magnetic or capacitive coupling, blocking common-mode interference paths.

(2) Power Isolation: The 5V power supply from the upper-level USB port cannot directly power the lower-level isolated circuit (the electrical connection must be disconnected). An isolated DC-DC power module (primary side connected to the upper-level 5V, secondary side outputting isolated 5V) is required to power the lower-level circuit (secondary side of the isolator, lower-level USB connector) to ensure the isolation voltage between the primary and secondary sides meets the standard.

(3) Isolation Level: The isolation voltage is selected according to the scenario requirements. Since this DIY product is intended for daily testing, the designed isolation voltage is 1500VDC/min.

Let's DIY together step by step! Hardware Solution:

1. Input Port: Use USB-C as the input port for direct connection to a computer;

2. Output Port: Use USB-A as the output port for direct connection to peripherals such as USB flash drives;

3. Power Supply:

(1) If the number of output ports is greater than 2, an auxiliary power supply is required; a 5V-0.6A USB-C port is recommended for the auxiliary power supply;

(2) It is recommended to use the CH217K chip for current limiting, limiting to 2A;

(3) Use a 5V power isolation chip to isolate the DC-DC power supply;

4. HUB Main Control Section:

(1) The main control chip needs to use a USB signal isolation chip and a hub; the isolated and non-isolated ends should be connected by a capacitor or a transformer to isolate the signal. The CH318 signal isolation chip and the CH334 hub are recommended.

(2) All power decoupling capacitors should be placed close to the chip pins, passing through the capacitors before reaching the chip pins to improve power stability and anti-interference capability. 5. Draw the schematic and PCB according to the recommended scheme above. Refer to the datasheet of the recommended chip for the recommended application circuit design and modifications.

Recommended Tools: Use free software KiCad or LCSC EDA to draw the schematic and PCB. After completion, you can commission a PCB manufacturer to make a prototype (cost approximately 10 RMB/5 boards, delivery in about 3 days).

Component Soldering: Before soldering, prepare a soldering iron (recommended temperature set to 320-350℃), solder wire (0.8mm lead-free solder), flux (to prevent cold solder joints), and wear an anti-static wrist strap (to avoid electrostatic discharge damaging the chip).

Casing Installation: You can use a 3D printer to print a casing. If you don't have a 3D printer, it's recommended to find a seller on Xianyu (a Chinese online marketplace) to print it for you; the cost is 15-20 RMB.

Power-on Test:

(1) For the first power-on, it is recommended to use a "current-limited power supply" (e.g., an adjustable DC power supply, initially set to 5V/100mA) to avoid short circuits and damage to components;

(2) If the chip does not get hot after power-on (normal temperature ≤40℃), connect the upstream USB female connector to the computer via a data cable; if "USB Root Hub (USB 2.0)" appears in the computer's "Device Manager," it indicates that the HUB chip is correctly recognized; insert a USB flash drive, mouse, or other device into the downstream USB female connector. If the computer can recognize and use it normally, it indicates that the data channel is normal; if it cannot be recognized, check: whether the D+ and D- signal lines are short-circuited/poorly soldered, whether the pull-up and pull-down resistors are correctly soldered, and whether the chip is soldered backwards.

By following the above steps, a stable USB 2.0 HUB can be obtained.