Input/Output Interfaces

5.7.2 USB Cable Data

The recommended cable length between the host and the USB device should be no longer than sixteen feet for full-channel (12 MB/s) operation, depending on cable specification (see following table).

Table 5-8.

USB Cable Length Data

Conductor Size

Resistance

Maximum Length

 

 

 

20 AWG

0.036 Ω

16.4 ft (5.00 m)

 

 

 

22 AWG

0.057 Ω

9.94 ft (3.03 m)

 

 

 

24 AWG

0.091 Ω

6.82 ft (2.08 m)

 

 

 

26 AWG

0.145 Ω

4.30 ft (1.31 m)

 

 

 

28 AWG

0.232 Ω

2.66 ft (0.81 m)

 

 

 

NOTE:

 

 

For sub-channel (1.5 MB/s) operation and/or when using sub-standard cable shorter lengths may be allowable and/or necessary.

The shield, chassis ground, and power ground should be tied together at the host end but left unconnected at the device end to avoid ground loops.

Table 5-9.

USB Color Code

Signal

Insulation color

 

 

Data +

Green

 

 

Data -

White

 

 

Vcc

Red

 

 

Ground

Black

 

 

 

5-12

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Technical Reference Guide