SN74AXC8T245-Q1: Data Rate

Ray Vincent Aranzaso

Mastermind 18180 points

Part Number: SN74AXC8T245-Q1
Other Parts Discussed in Thread: SN74AUC245, SN74AXC8T245

Hi,

Good Day.

Customer would like to use SN74AXC8T245-Q1 in an RGMII application with 1.8V to 1.8V translation.

The data rate mentioned in the datasheet is "Up to 380 Mbps support when translating from 1.8V to 3.3 V".

Customer do not find the data rate when translating 1.8V to 3.3V.

Could you please give us these information.

The data rate required is 250Mbps min on each RGMII lines.

Is this transceiver compliant with these requirements?

Please advise. Thank you very much.

Best Regards,

Ray Vincent

over 4 years ago

0 Dylan Hubbard over 4 years ago

TI__Mastermind 47735 points

Hi Ray,

1.8 V to 1.8 V isn't really translation. I recommend a buffer for this instead, I'll move your thread over to the Logic group who can help you find suitable buffers.

0 Emrys Maier over 4 years ago in reply to Dylan Hubbard

TI__Guru* 97666 points

Hi Ray,

I'd recommend to use the SN74AUC245, as it provides the fastest operation available at 1.8V.

I'm afraid I am not an expert on the RGMII specification - it would be up to the customer to determine if the device provides the required performance for their system.

0 Ray Vincent Aranzaso over 4 years ago in reply to Emrys Maier

TI__Mastermind 18180 points

Hi Emrys,

Good Day. Please see below the response of our customer to your reply. Thank you very much.

Indeed, in the case of our application we are not doing a level translation.
This involves performing an isolation on 2 domains (having the same voltage level) using the component SN74AXC8T245 (-Q1).
To keep it simple, we need to know the minimum Data Rate of SN74AXC8T245 (-Q1) component for a voltage level of 1.8V.

Best Regards,

Ray Vincent

0 Dylan Hubbard over 4 years ago in reply to Ray Vincent Aranzaso

TI__Mastermind 47735 points

Hey Ray,

No, I do not believe the SN74AXC8T245-Q1 device will meet those RGMII requirements at 1.8 V. RGMII has very strict timing parameters that are difficult to meet.

0 Ray Vincent Aranzaso over 4 years ago in reply to Dylan Hubbard

TI__Mastermind 18180 points

Hi Dylan,

Good Day. Please see below the response of the customer to your reply. Thank you very much.

Do you have a reference that corresponds to our needs to propose to us:
- translation from 1.8V to 1.8V for RGMII signals (250Mbps)?

As I said, we need to translate RGMII from 1.8V(VCCA) to 1.8V(VCCB). The 2 power domains VCCA and VCCB have the same levels but are not from the same source; hence our need to have a buffer with 2 power supply references (isolation).

Best Regards,

Ray Vincent

0 Clemens Ladisch over 4 years ago in reply to Ray Vincent Aranzaso

Guru 325310 points

With a 1.8 V supply, the SN74AUC245 accepts any input voltages between 1.17 V and 3.6 V.

0 Dylan Hubbard over 4 years ago in reply to Ray Vincent Aranzaso

TI__Mastermind 47735 points

Hey Ray,

No, i'm not sure we have a device suitable for this application. Can you elaborate more on the need for isolation between the two power domains? Its possible this is still something that can be accomplished with a buffer.

Logic

Logic forum

SN74AXC8T245-Q1: Data Rate