dell precision 5540 + 2 x S2721QS 4k

Question

Hi all, owning a precision 5540, I'm about to buy two S2721QS (3840 x 2160). I would like two know which docking station should I buy in order to support both monitors at 60hz.

Your help would be much appreciated.

Thanks

jphughan · Accepted Answer

@Hord122  Display setup doesn't affect dock power supply requirements.  But the system model you're docking absolutely does.  You have a Precision 5540, which is designed for a 130W power source.  In order to for the dock to provide 130W to the system, the dock itself needs to be powered by a 180W source.  When the dock only has a 130W source, it only passes through 90W to the system.  Running your 5540 from a 90W source can lead to slower battery charging and reduced performance as the system attempts to adapt to an undersized power source.  The reason you need a 180W source for 130W passthrough and a 130W source for 90W passthrough is because the dock needs some power to run its own internal electronics and provide power to USB devices you might attach.

jphughan · Answer

@Hord122 You'll need a Thunderbolt 3 dock.  But the Precision 5540 is designed for a 130W power source, which is above the 100W max of the USB PD spec.  Dell did something proprietary on some of their docks to stretch the spec to 130W specifically to support systems like this, but you won't find that implemented elsewhere.  The only dock that will run dual 4K displays and provide that much power to your system is the WD19TB or the WD19TBS.  The latter is identical to the former except it drops the 3.5mm headset jack.  There's some parts shortage that prevented Dell from building those jacks or getting the audio chipset that runs it, so they created 'S' versions of their WD19 dock family models that don't include them.  Note that the WD19TB(S) has specific cabling requirements when dealing with 4K displays, and those vary based on the capabilities of the system.  The Precision 5540 is a DisplayPort HBR2 system, which means that to run dual 4K 60 Hz displays, one of them will need to be plugged into the 'downstream TB3' port at the edge of the dock -- not to be confused with the USB-C port near the HDMI output.  Use a USB-C to DisplayPort adapter/cable since your displays don't have USB-C ports.  The other display can be connected to any other output on the dock.

Hord122 · Answer

Thanks for the answer, but will I need a 180W dock to run both monitors @60hz or is the 130W enough?

Precision Mobile Workstations

dell precision 5540 + 2 x S2721QS 4k

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