Usb Cable Length - Smart Technologies Board 600 series Connection Manual

USB Cable Length

The maximum allowable USB cable length is determined primarily by signal attenuation and
propagation delay. A USB cable also carries VBUS and GND wires on each segment to deliver
power to bus-powered devices. VBUS is nominally +5V at the source, and the GND lead provides
a common ground reference between the upstream and downstream devices. The voltage drop
across the VBUS and GND leads can also limit the maximum cable length.
You can purchase or manufacture cables using commonly available wire that conforms to USB
specifications to a maximum length of approximately 16 feet (5 meters).
Extending USB Connections
In USB topology, the hub is the only device that you can use to link USB devices. The distance
between hosts and devices, therefore, is limited by the maximum USB cable length allowed
between devices and the maximum number of hubs allowed in a path.
In the following diagram, you can see that if all USB hub connections use 16' (5 m) cables, the
maximum distance between a host's root hub and a function is: 6 × 16' (5 m) = 96' (30 m).
Host (Tier 1)
Host
Root
Hub
16' (5 m) + 16' (5 m)
Connecting a compound device limits the maximum distance to: 5 × 16' (5 m) = 80' (25 m).
Host (Tier 1) Tier 2
Host
R oot Hub
Hub
16' (5 m) +
NOTE: SMART Board 600i interactive whiteboard systems and SMART Board 600 series
interactive whiteboards with the speaker option (SBA) are compound devices.
Connecting a compound device and a host with an internal non-root hub further limits the
maximum distance to: 4 × 16' (5 m) = 64' (20 m).
Host with
Internal Non-
Host (Tier 1)
Root Hub
Host
Root
Hub
20
Tier 2 Tier 3
Hub Hub
1 2
+ 16' (5 m)
Tier 3
Hub
1 2
16' (5 m) + 16' (5 m)
Tier 2
Hub
1
16' (5 m)
USB 2.0 Specification Primer
Tier 4 Tier 5
Hub Hub
3 4
+ 16' (5 m) + 16' (5 m)
Tier 4 Tier 5
Hub Hub
3 4
+ 16' (5 m) + 16' (5 m) = 80' (25 m)
Tier 3 Tier 4
Hub Hub
2 3
+ 16' (5 m) + 16' (5 m)
Tier 6 Tier 7
Hub
Function
5
+ 16' (5 m) = 96' (30 m)
Tier 6 Tier 7
Hub
Function
5
Tier 5 Tier 6
Hub Hub
4 5
+ 16' (5 m) = 64' (20 m)
Compound
Device
Tier 7
Function