SN74AXC2T245: Regarding Data rate

kakeru manita

Prodigy 50 points

Part Number: SN74AXC2T245

HI Team,

1.Regarding MAX data rate

The data rate is listed as Max380 Mbps when the signal is converted from 1.8V to 3.3V.

Does the Max data rate change depending on the voltage being converted?

For example, if 3.3V is converted to 1.2V, what is the maximum data rate?

Is there any material that shows the relationship between conversion voltage and max data rate?

2.Regarding Min data rate

What will be the min data rate?

Best Regards,

4 months ago

0 Clemens Ladisch 4 months ago

Guru 267530 points

1. The maximum data rate indeed depends on both supplies. See the propagation delay specifications in sections 5.6…5.13, but there is no easy way to convert that into a frequency.

2. CMOS devices have no minimum; they can handle 0 Hz.

0 kakeru manita 4 months ago

Prodigy 50 points

Hi Clemens,

Thank you for your reply.

Please tell me how to calculate frequency from propagation delay.

0 Michael Ikwuyum 4 months ago in reply to kakeru manita

TI__Mastermind 27990 points

Hi Kakeru,

You may do (1/Tpd) * 1000 to give you MHz as a reference. However, please note that data rate depends on the system designers tolerance for various parameters, so will generally need to be tested in the specific application environment for the clearest understanding of signal integrity and would further recommend also verifying using the EVM per the system/loading requirements, thanks.

Best Regards,

Michael.

0 kakeru manita 4 months ago in reply to Michael Ikwuyum

Prodigy 50 points

Hi Michael,

Thank you for your reply.

Please tell me how to calculate frequency from propagation delay.

For example, when VCCA=3.3V and VCCB=1.8V, A→B is -40℃~-85℃ Tpd Max 5ns, so is the reference frequency (1/Tpd) * 1000=200Mbps?
In the case of B→A, the Tpd Max is 4ns at -40℃~-85℃, so is the reference frequency 250Mbps?

The calculated value is just a reference frequency, right?

Best Regards,

kakeru.

+1 Clemens Ladisch 4 months ago in reply to kakeru manita

Guru 267530 points

Yes, these 200 Mbps and 250 Mbps values are safe estimates for the maximum data rate.

(The actual maximum data rate is likely to be higher because it is possible to switch the input for the next bit some time before the output has completed switching for the current bit. But this time is not specified and would have to be measured.)

0 kakeru manita 4 months ago in reply to Clemens Ladisch

Prodigy 50 points

Hi Clemens,

Thank you for your reply.
Isn't the method of calculating the maximum frequency equal to (1/(Tpd+Tpd)) * 1000?
Is the Tpd listed in Sections 5.6…5.13 the sum of the rising and falling Tpd?

Best Regards,

kakeru.

+1 Clemens Ladisch 4 months ago in reply to kakeru manita

Guru 267530 points

Tpd corresponds to a single bit, measured in Mbps.
Tpd+Tpd corresponds to two bits, which would be a singe cycle of a square wave, measured in MHz.

0 kakeru manita 4 months ago in reply to Clemens Ladisch

Prodigy 50 points

Hi Clemens,

understood. thank you.
Why does the Max frequency change depending on the voltage?
Is it because the waveform rises and falls slowly?

Best Regards,

kakeru.

0 Clemens Ladisch 4 months ago in reply to kakeru manita

Guru 267530 points

The gate-to-souce voltage of the transistors is V_CC, so a higher supply implies a higher drive strength, which allows faster (dis)charging of the gate and load capacitances.

Logic

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SN74AXC2T245: Regarding Data rate