Plugable TBT4-UDZ Dock Review and Teardown

[2023/03/07 – added brief comparison to Dell, HP, and Lenovo quad-monitor docks]

1. Introduction
   1. Product Specs
2. Unboxing & Physical Characteristics
3. Functional Testing
   1. Monitors
   2. Power
   3. USB device performance
4. Teardown
5. PCB Details
   1. Component Topology
   2. Analysis
6. Conclusion

Introduction

During my time as a program manager in DirectX at Microsoft, I frequently interacted with GPU vendors like AMD, Intel, and NVIDIA, but also accessory partners that made docking stations. A big focus during Windows 7 and Windows 8 development was making multi-monitor support more robust, especially for the emerging market of USB-connected monitor adapters from DisplayLink and the like. Plugable, is a PC accessory company located just a few miles away from Microsoft HQ and partner closely with DisplayLink and Microsoft. I have fond memories of those times and it was always a pleasure to work with the Plugable team. Over the years, many of Plugable’s products have been re-brands of generic ODM models manufactured by large Chinese vendors, but they have designed unique category-defining products as well. One of their USB 3.0 docks is still one of the most popular docks on Amazon almost 10 years after launch with a 4.6 star average over ~11K ratings – because it just works. Unlike so many other laptop accessory brands, Plugable has a well-trained staff that does support *right*. I’m continually impressed by their responsiveness on forums and attention to detail. So it is with great pleasure that I’m able to review Plugable’s latest flagship product, the TBT4-UDZ Thunderbolt 4 Dock.

Full disclosure: While this is not a sponsored post, the product(s) reviewed were provided at no cost for evaluation purposes. Products received in this capacity are destined for teardowns, future device interoperability testing, and/or charitable donations.

Product Specs

With 100 different Thunderbolt4/USB4 options on the market, it is difficult to differentiate a new market entrant. The one thing that stands out with the TBT4-UDZ is that that it foregoes a downstream Thunderbolt port in favor of more monitor and USB ports. I reckon Plugable has done the research and found that the “killer” features (external GPU and storage arrays) of extra Thunderbolt ports are not popular with typical laptop users. Also not popular? USB-C dongles. And with two HDMI and two DisplayPort receptacles, you don’t need no stinkin’ dongles with the TBT4-UDZ.

Feature Summary:

• 2x Displayport 1.2
• 2x HDMI 2.0b
• Quad 4K 60
• 1x USB-C 10Gb/s 7.5W
• 3x USB 10Gb/s 4.5W
• 2x USB 3.0 4.5W
• 1x USB 2.0 / 7.5W
• 2.5Gb/s Ethernet
• SD card reader
• 3.5mm combo audio
• 135W PSU

Unboxing & Physical Characteristics

Like other flagship docking stations, the TBT4-UDZ packaging, build construction, and accessories are all high-quality. The TBT4-UDZ dock itself has a beautiful brushed aluminum finish with rubber end-caps while lower tier Plugable products tend to have glossy black plastic everywhere.

The box was shrink-wrapped thin cardboard. Popping the single tab revealed an inner cardboard tray colored with Plugable’s signature deep green holding the dock securely. Under the dock was a user guide and product support card. Under the tray were the power supply, Thunderbolt cable, and a vertical stand for the dock.

The power supply model is PA-1131-72 (20V@6.75A – 135W) by LiteOn with a 7.4x5mm barrel jack on a 1.5m cable and a detachable 1.0m 3-prong AC/Mains cable. The included Thunderbolt cable is 1m instead of the typical 0.8m included with other dock brands.

[click the photos for hi-resolution versions]

Cardboard box

Contents

Dock, PSU and vertical stand

PSU: 584g

Dock: 637g

Stand: 246g

Cable: 43g

Cable is 1m as advertised

195mm

104mm

36mm

145mm

65mm

31mm

73mm

141mm

7mm

rubber bottom

Functional Testing

Test setup with Surface Laptop Studio

The first thing I noticed about the dock was that unlike other brands, the power button actually worked to switch my laptop on and off! I have tried several docks over the past 2 years and none of them had a power button that actually worked reliably. I’m not sure if this is a fault of Windows, my laptops. or the docks, but this was a pleasant “first kiss” experience.

After running on its side, I tried placing the dock in the included vertical stand – its an interference fit between two aluminum parts and it felt like I was going to scratch one or both parts if I pressed them together tightly, so I didn’t fit them together all the way. But the stand worked and is heavy enough to prevent the dock from toppling over when plugging in cables. The rubber bottom gave decent grip, but for some cables I still had to take the two handed approach – one hand to manipulate the cable and the other to stabilize the dock. I tend to prefer my dock laying flat even though it takes up a little more desk space, but its really not a good idea with this dock because there are no rubber bumpers to protect your desk from the aluminum. I think Plugable should have included a packet of clear rubber bumpers in the box just so folks have the option.

Other than that, the dock just works. When Thunderbolt 4 docks were new, I had all sorts of issues that needed firmware updates. But with the market maturing, Plugable has a product that runs flawlessly out of the box. I had no issues plugging and unplugging many different USB devices, monitors, SD cards, etc. A 2.4GHz wireless keyboard and mouse worked OK even when running Ethernet traffic, SSD transfer, and an SD card transfer simultaneously.

Monitors

When using my built-in Laptop screen, only 3 external monitors can be used, but once the laptop screen was switched off, I could do 4 monitors just fine. This is a limitation on most laptops. I like my Laptop Studio screen so I left it on for testing after I verified that all 4 monitor ports worked. Although Plugable advertises 4x 4K60 monitors, I don’t have 4 to test with so I used 1080p and 1440p instead.

Todo: test high refresh rates – does 120Hz or 144Hz work? Plugable doesn’t list it in the spec sheet and I don’t have any monitors to test with currently…

Power

Unlike Plugable’s last generation TBT3-UDZ which included a 170W PSU, the TBT4-UDZ includes a smaller 135W brick. Both are able to drive 95W+ to the laptop for charging, but the older model is also able to drive all the included USB ports at maximum power simultaneously. The new model is not able to do this. If you plug in too many high power USB devices like hard drives or cell phones, laptop charging will ramp down to ~60W. Plugable probably did this for cost-savings. In reality, situations where all the USB ports are running at full power are rare so its unlikely this would be a problem for anyone. But it is still worth noting.

Running Furmark stress

I was able to confirm that the dock can provide ~95W charging by first depleting my laptop battery 50% and then running Furmark stress while plugged into the dock. I plugged a whole bunch of USB devices in and observed the PSU being overdriven past its 135W rating slightly (I think it hit 139W, but I didn’t get a photo). Power sent to the laptop dropped to 60-80W with no hiccups. All the USB ports were able to do 4.5-5W consistently with the USB-C and USB 2.0 ports outperforming their rated 7.5W by a small margin at 8-10W. The only issue I had was when I plugged in a 3rd-party bus-powered USB-C hub into the sole USB-C port. After loading up the hub with several high power devices, I observer inconsistent behavior on the USB ports – I think the 3rd-party hub was resetting itself over and over when it ran out of power. After unplugging the hub, everything returned to normal operation.

USB device performance

Testing USB device throughput/performance is not terribly interesting to me. I did use an external 10Gb/s SSD enclosure which ran at the expected speeds of 800-900MB/s. Let me know if there is any further interest and I’ll see if I can get additional testing done.

Teardown

The teardown was a little more involved than the last few docks I’ve disassembled, but the assembly was logical with little wasted space. First, I heated the two rubber end caps with a hair dryer to soften the adhesive holding them in place. Then I carefully pried them away from the aluminum chassis with a plastic spudger tool. This revealed two Philips (+) screws adjacent to the power button. After loosening the screws, I was able to slide the outer aluminum shell away revealing a black plastic mid-frame holding the PCB. After loosening 4 more screws, the midframe popped free revealing the PCB covered in shiny shielding. The power button fell off the midframe at the same time

A 49g heatsink was adhered to one side of the PCB which I removed revealing some small thermal pads. I then peeled back the rigid metal cage from one side and foil shield on the other side to reveal the actual PCB. During the process I noticed a thin foam pad surrounding the 3.5mm audio jack and a fabric pad covering the power button which seems to provide some damping effect to get a more solid sounding click. Nice attention to detail!

[click photos for hi-res versions]

2 rubber caps and 2 screws

Inner chassis slides out

plastic mid frame and power button detaches after loosening 4 screws

plastic mid frame closeup

PCB has excellent shielding with insulated foil on one side and a metal cage on the other

Audio, TB4, and power

Closeup of shielding and thermal pads

Heatsink

Audio TB4, and power fully disassembled

PCB Details

[click photos for hi-res versions]

PCB top

PCB bottom

Component Topology

• TB4 upstream port
  • Infineon/Cypress CYPD5235-968BZXI 2-port USB-C & PD controller
  • Parade/Fresco FL5801-2@2 5-port USB2 port expander
    • Silicon Labs CP2112 USB -> SMBus bridge
      • Diodes Inc/Pericom PI4MSD5V 4-channel I2C Mux/Switch
        • links to flash chips for firmware upgrades?
    • RealTek ALC4030 audio
      • 3.5mm TRRS jack
    • USB 2.0 port #1
    • USB 2.0 link to JHL8440 chip
  • Intel JHL8440 Thunderbolt controller
    • RealTek RTD2188 MST display controller #1
      • DP #1
      • HDMI #1
    • RealTek RTD2188 MST display controller #2
      • DP #2
      • HDMI #2
    • Infineon/Cypress CYUSB4357-BZXT USB 3.2 Gen2 5-port hub with PD
      • USB-C 10Gb/s
      • Infineon/Cypress CYUSB3314-88LTXC USB 3.0 4-port hub
        • RealTek RTL8156BG 2.5Gb/s Ethernet
          • RJ45 Ethernet port
        • USB 3.0 5Gb/s #1
        • USB 3.0 5Gb/s #2
        • Genesys Logic GL3231S USB 3.1 Gen1 dual LUN SD card reader
          • SD reader
          • microSD reader
      • USB 3.2 10Gb/s #1
      • USB 3.2 10Gb/s #2
      • USB 3.2 10Gb/s #3

In addition I found the following flash and power ICs

Flash ROM ICs

• PuyaSemi P25Q80h 8Mb flash x2
• PuyaSemi P25Q16SH 16Mb flash x2
• PuyaSemi P25Q21h 2Mb flash
• PuyaSemi P25Q64SH 64Mb
• unbranded P24C2 2Mb flash (U91)
• unoccupied solder pads for additional flash chip

Power ICs:

• Anpec APW8713 8amp PWM converter x3
• unknown chip wQ7HDF
• Sinopower SM3331 p-channel mosfet x2
• Sinopower SM3331 p-channel mosfet
• Sinopower SM3439N N-channel mosfet x2

Analysis

The PCB is labelled “EHDDR9 7D28DR900COH1 Rev.B1”. A key design element is the thick copper ground trace at the perimeter on both sides. It seems a large focus of the design is minimizing EMF interference since this trace, along with conductive foam pads and tape, is used to ground the foil and rigid metal shields. Compared to other dock station PCBs, this example has many more large polymer caps – 11 compared to just 1 on the Sparkle dock I disassembled last year. Clearly, Plugable is not taking any chances with power filtering either.

For each of the seven flash rom chips, 8 bare copper pads are exposed close by. Presumably, these are used for bench-programming to speed up the assembly line rather than wait for an external programmer to run via USB. There appears to be an 8th spot for a flash chip that is vacant but still has the 8 pads. A few additional test points are exposed around the board as well.

Through a contact, I was able to get my hands on the Realtek RTD2188 spec sheet, a brand new DisplayPort MST chip. It shows that the RTD2188 is capable of HDMI 2.1 with variable refresh rate and DP 1.4 w/DSC for up to 8K60 or 4K240 resolution. In addition, there are three output transmitters, one dedicated to DP 1.4, and two that can do DP++ or HDMI 2.1. These Realtek chips seem to have leapfrogged the competing Synpatics VMM MST chips in terms of functionality so its a shame that Plugable isn’t using them to their fullest and only claiming support for 4K60 monitors. But maybe that will change with firmware updates? Given the added cost, I’m not exactly sure why Plugable decided to use two Realtek MST chips. I think the dock could have been done with 3 monitors attached to a one MST chip with the fourth monitor attached directly to the Intel JHL8440 since no downstream TB4 ports are included. With that scheme, I don’t think all 4 monitors would run at 4K60 simultaneously, but it could be 3x 4K60 + 1x 4K30 which is pretty close for a lot less cost and complexity.

Conclusion

I really like the construction of this dock. All the components from the extruded aluminum chassis to the internal heatsink are excellent quality. I especially liked the attention to detail with the foam and fabric covers for the audio jack and power switch as damping material to provide better feel when clicking the button and plugging in headphones. The EMF shielding is the *best* I have ever seen on a docking station product. Really nice job there!

The one drawback of this dock is the lack of a downstream Thunderbolt 4 port. As noted earlier, Plugable made a bold choice to exclude that port as this cuts out a segment of the market that may want to use external GPUs or high speed attached storage. But that market segment already well-covered by other products. What isn’t well covered in the market is a quad monitor capability where all ports can do 4K60 simultaneously without any DisplayLink lag/latency and without the need for USB-C monitor dongles/adapters. So Plugable has made this tradeoff and launched an good product to fit that niche. Is this product useful outside that niche? You bet! Out of the box, it was the smoothest install experience I have had with any Thunderbolt Dock. For any scenario where you don’t need downstream a Thunderbolt port, I would have no problem recommending this dock. As a more premium brand, you pay a bit more for Plugable ($299 list on Amazon), but you also get the best warranty (2 years) and best technical support available. I just wish Plugable had included more USB-C ports instead of the old USB A style.

Currently there are three docks that compete directly with Plugable: Dell, HP and Lenovo. All are able to support quad monitors without DisplayLink’s lag/latency and include downstream Thunderbolt ports, but do not include audio or SDCard readers.