SN75179B

Ankit Agrawal

Other Parts Discussed in Thread: SN75179B, SN65HVD379, SN65HVD179

Hi,

One of the customers has the following problem, please guide.

To design USB Version 2.0 to CAT5 Converter (Tx Rx Pairs) which can convert USB Version 2.0 to CAT5 at local end and can travel CAT5 signal to minimum 100m and at far end this CAT5 signal can be converter to USB port. The similar type Product: http://www.gefen.com/kvm/dproduct.jsp?prod_id=5529 and for this they have seen our Part # SN75179B.

Kindly guide me if can this IC support / meets his requirement? If yes - do you have more details for the application with test Schematic / EV Boards? If No, please help me to get the solutions for this.

Please reply with details.

Best Regards,

Ankit Agrawal

over 15 years ago

0 Clark Kinnaird over 15 years ago

TI__Expert 3945 points

Hi Ankit,

The SN75179B is a full-duplex driver/receiver for RS-422/RS485. At 100 meter length on CAT5, the signals will be okay for low-speed USB (1.5 Mbps) and maybe at full-speed USB (12 Mbps). For high-speed USB (480 Mbps) the twisted-pair lines will have too much distortion due to the low-pass effects of the long cable. If full-speed is sufficient, there are newer devices with the same pin-out as the SN75179B. A direct drop-in replacement with lower power would be the SN65HVD179. If a 3.3V supply is an advantage, you could consider the SN65HVD379.

Looking at the GEFEN extender you reference above, I expect this device uses all four twisted-pairs in the link to acheive the high-speed operation. That would require multiplexing the 480 Mpbs USB data onto the four pairs at effectively 120 Mbps each. Even at 120 Mbps, standard RS-485 will not support a cable length of 100 meters, so either some coding scheme or receiver equalization (or both) will be required.