SN74AVC8T245: SN74AVC8T245

qiang hao

Part Number: SN74AVC8T245
Other Parts Discussed in Thread: SN74AXC8T245

Hi,

I am plan to use SN74AVC8T245 to translate USB signal by ULPI interface which the data rate is 60Mbps per channel.

The usb signal is bi-directional, so I want to know how long will it be active if I switch the direction from A to B to B to A.

I checked with USB PROTOCOL, the switching time should within 16ns, I am not sure whether this chip can meet the requirement, please help with confirm.

And also, I saw there is a layout requirement that the PCB trace should be short with this chip, do you have more specific requirement of this?

Because in our path, there will be one 1m cable, two 10cm cable and 20inch pcb trace, do we have any risk of this path?

Thanks,

Qiang

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 289310 points

The SN74AXC8T245 is faster.

The outputs are controlled both by DIR and by /OE. The DIR switching times should be the same as the /OE propagation delays.

USB signals are designed to be transmitted over cables; ULPI signals are not. That 1 m cable should be a USB cable.

0 qiang hao over 1 year ago in reply to Clemens Ladisch

Prodigy 20 points

Hi,

Why the SN74AXC8T245 is faster?

I saw from the datasheet, for 1.5v-1.8v translation, SN74AVC8T245 has 5.1ns delay from B to A and SN74AXC8T245 has 7ns delay.

Thanks,

Qiang

0 Michael Ikwuyum over 1 year ago in reply to qiang hao

TI__Mastermind 34925 points

Hi Qiang,

Depending on the voltages and temperature, AVC may be faster. For your use case, you may use AVC if faster, thanks.

Best Regards,

Michael.

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SN74AVC8T245: SN74AVC8T245