skobzar
2 Bronze

U3421WE, longer USB Type-C cable?

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Hello

I have Dell U3421WE monitor connected to Dell XPS 7590 laptop by USB Type-C cable. Original cable works well but it is 1m in length only. But 2m cable is needed. I tried Belkin Thunderbolt 3 F2CD085BT2M-BLK and Startech Thunderbolt 3 TBLT3MM2MA cables and both do not work - laptop is charging but monitor is blank. I saw this USB Type-C monitors FAQ, but not sure exactly which cable I need. Could you advise?

Thank you!

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jphughan
7 Gold

Re: U3421WE, longer USB Type-C cable?

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@skobzar  A 2m Thunderbolt 3 cable will almost certainly be an active Thunderbolt 3 cable, and active Thunderbolt 3 cables only work as USB 2.0 + power cables when used in non-Thunderbolt scenarios.  The pins within a USB-C connector that carry USB 3.x data and video are the same pins used for TB3 when TB3 is used, and USB 3.x and video are apparently not compatible with the electronics used to create active TB3 cables.  You need a regular USB-C cable that supports USB PD up to 100W rather than just 60W, and USB 3.x Gen 1 (5 Gbps) and video, like this one.  It's 1.8m.  Hopefully that's close enough for your purposes.  Cables that support USB 3.x Gen 2 (10 Gbps) are still limited to 1m today, and your display doesn't support that anyway.  The only exception is an active USB-C cable I know about by Cable Matters, which supports video and USB 3.x Gen 2 over 3m, but it also only supports USB PD up to 60W, whereas the display is capable of 90W.  That said, you really shouldn't rely on the display as a power source for your XPS 15 anyway, since that system is designed for a 130W power source, so even if you get the full 90W from the display, the display will be an undersized power source for that system, which means you can experience slower battery charging and reduced performance.  Dell as of this writing doesn't have any USB-C displays that can provide 130W.  The only way to do that is with certain Dell docks.

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jphughan
7 Gold

Re: U3421WE, longer USB Type-C cable?

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@skobzar  A 2m Thunderbolt 3 cable will almost certainly be an active Thunderbolt 3 cable, and active Thunderbolt 3 cables only work as USB 2.0 + power cables when used in non-Thunderbolt scenarios.  The pins within a USB-C connector that carry USB 3.x data and video are the same pins used for TB3 when TB3 is used, and USB 3.x and video are apparently not compatible with the electronics used to create active TB3 cables.  You need a regular USB-C cable that supports USB PD up to 100W rather than just 60W, and USB 3.x Gen 1 (5 Gbps) and video, like this one.  It's 1.8m.  Hopefully that's close enough for your purposes.  Cables that support USB 3.x Gen 2 (10 Gbps) are still limited to 1m today, and your display doesn't support that anyway.  The only exception is an active USB-C cable I know about by Cable Matters, which supports video and USB 3.x Gen 2 over 3m, but it also only supports USB PD up to 60W, whereas the display is capable of 90W.  That said, you really shouldn't rely on the display as a power source for your XPS 15 anyway, since that system is designed for a 130W power source, so even if you get the full 90W from the display, the display will be an undersized power source for that system, which means you can experience slower battery charging and reduced performance.  Dell as of this writing doesn't have any USB-C displays that can provide 130W.  The only way to do that is with certain Dell docks.

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skobzar
2 Bronze

Re: U3421WE, longer USB Type-C cable?

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@jphughanthank you very much for extended reply.

I do not worry much about power consumption because it is Core i5 low-loaded laptop. It is always connected to monitor and always fully charged.

My mistake is that I bought TB3 cables but I need regular USB-C (3.x) Gen 1 (5 Gbps) active cable with 100W PD. Right?

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skobzar
2 Bronze

Re: U3421WE, longer USB Type-C cable?

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I found similar cable from seller which is very close to me. Cable looks good and has positive feedback on Amazon. Do you think it will work?

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jphughan
7 Gold

Re: U3421WE, longer USB Type-C cable?

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@skobzar  Happy to help.  You don't need an active USB-C cable for your purposes, assuming 1.8m is sufficient.  You just can't use an active TB3 cable for your purposes, because your display doesn't use Thunderbolt 3.  The Choetech cables you linked only support power and USB 2.0 data, so no they would not work.

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skobzar
2 Bronze

Re: U3421WE, longer USB Type-C cable?

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@jphughan  got it. Thank you!

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skobzar
2 Bronze

Re: U3421WE, longer USB Type-C cable?

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@jphughanI can confirm cable you recommended above works well. Thank you very much!

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jphughan
7 Gold

Re: U3421WE, longer USB Type-C cable?

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@skobzar  Thanks for reporting back, and glad to hear you've got a good solution!

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