Lenovo Thunderbolt 4 Dock unboxing and teardown

[Don’t forget to check out the other 15 Thunderbolt 4 Docks]

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I bought the Lenovo Thunderbolt Dock 4 on launch day and did a teardown. Here are the results:

Feature summary

• 100W PD charging (limited by 135W PSU)
• 4x USB 3.2 Gen2 10Gb/s (4.5W power)
• 1x USB-C 10Gb/s (up to 15W power)
• 1x Gigabit Ethernet
• 1x 3.5mm Audio
• 1x HDMI 2.1
• 2x DP 1.4
• 1x USB4/TB4 downstream port (up to 15W power and with DP 1.4 alt mode)
• Quad monitor capable

I confirmed that regular USB-C laptops can run 2x 4K30 displays on any combination of display output ports. I’m not sure if 2x 4K60 is possible since I don’t have the monitors to test yet.

Unboxing and component weights

Typical Lenovo simplicity. The box contained the Dock, TB4 cable, and 135W power supply in separate baggies along with user and warranty guides. The power supply with 3-prong AC/mains cable weighed 541g, the dock 443g, and the 70cm cable 34g.

Teardown

The teardown was straightforward. First, I pulled off 4 rubber pads and the serial number label to reveal 5 Philips (+) screws. Once the screws were removed, I pried off the red panel revealing the PCB. Then I loosened two more Philips screws and unclipped the 4-pin cable for the power button. One of the rear-facing USB-C ports held the PCB in place so I bent the chassis slightly to free it. Once freed, the PCB popped out revealing a machined aluminum weight/heatsink (168g) with attached thermal pads.

Full PCB photos

Its a modular assembly with a separate power regulator daughter board connected to the mainboard via two 20-pin headers. I suspect the only difference between this model and a future model supporting 300W workstation class power is the daughter board. A tiny PCB with an illuminated switch was fastened to the main black plastic chassis and connected to the main board with a 4-pin cable.

Closeup PCB photos

Note the 5-pin header likely used for bench programming firmware and dozens of test pad points for automated QC.

Analysis

I love the design of this dock with its modular power regulator! I haven’t had much time to analyze this other than chart the components.

• Control chips:
  • Intel JHL8440 TB4 controller
  • Intel S0383L59 companion chip to handle MAC address forwarding (56-pins)??
  • SiliconLabs UB20F64G MCU
  • Cypress CY7C65219 Dock management controller
  • OnSemi NCP81239 4-switch Buck-Boost power controller (on daughter board)
• Feature chips:
  • Via Labs VL822L-Q8 4-port USB 3.x Gen2 hub controller
  • Via Labs VL822L-Q7 4-port USB 3.x Gen2 hub controller
  • Cypress CYPD5235 Dual USB-C controller
  • Parade/Fresco Logic FL5801 5-port USB 2.0 port expander
  • Synaptics VMM6212 USB-C -> DP+HDMI 2.1
  • Synaptics VMM53328 3-port DP HBR3 MST hub
  • Synaptics/Conexant CX21985 audio
  • Realtek 8153 Gigabit Ethernet
• Flash chips:

Here is my best guess of the topology after following the PCB traces:

• Intel JHL8440 TB4 controller
  • TB4 rear-facing port
  • Via Labs VL822L-Q8 4-port USB 3.1 Gen2 hub controller
    • Cypress CYPD5235 Dual USB-C controller
      • USB-C front facing port
      • Loopback to TB4 upstream port for PD functions?
    • USB 3.x front-facing port
    • USB 3.x rear facing port
    • Via Labs VL822L-Q7 4-port USB 3.1 Gen2 hub controller
      • 2x USB 3.x rear-facing ports
      • Realtek 8153 Gigabit Ethernet
        • Intel S0383L59
          • Ethernet Port
      • Synaptics/Conexant CX21985
        • 3.5mm audio
      • Parade/Fresco Logic FL5801 USB 2.0 port expander
        • SiliconLabs UB20F64G MCU
        • Cypress CY7C65219 Dock management controller
          • Flash chips?
        • Loopback to Intel S0383L59?
  • Synaptics VMM53328 3-port DP/HBR3 MST hub
    • DP 1.4
    • Loopback to downstream TB4 port?
    • Synaptics VMM6212 DP/HBR3 splitter
      • HDMI 2.1
      • DP 1.4

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