SN74LV245A: Delay time variation

Hiromu Susami

Part Number: SN74LV245A
Other Parts Discussed in Thread: SN74LVC245A,

Tool/software:

Hi team,

When I check tpd, ten and tdis (at Vcc=3.3V), the max variation is 16.5ns. Is the delay variation between "channel-to-channel" and "element difference" really so much? I don't care much about the delay between inputs and outputs.

Is there any device with shorter delay variation? My first thought is SN74LVC245A. If it is 8ch, it is the best. I understood differential interface has better delay variation.

Regards,
Hiromu

4 months ago

0 Ian Graham 3 months ago

TI__Genius 12141 points

Hi Hiromu,

This delay is between all devices and has a large buffer zone, because it is what TI guarantees the part to do. While I would expect the real delay variation, especially in a single device, to be much, much lower, TI does not guarantee that.

Best,

Ian

0 Hiromu Susami 3 months ago in reply to Ian Graham

TI__Intellectual 840 points

Hi Ian,

If we need to gurantee that, could you tell me some recommended devices?

Regards,
Hiromu

0 Hiromu Susami 3 months ago in reply to Hiromu Susami

TI__Intellectual 840 points

Hi Ian,

We are looking for devices that variaion of delay are guranteed <2nsec(at least <5nsec). A large delay time is acceptable if variation is small.

Regards,
Hiromu

0 Albert Xu1 3 months ago in reply to Hiromu Susami

TI__Mastermind 40655 points

Hi Hiromu-san,

We do not have any devices that can guarantee this low of variation.

0 Hiromu Susami 3 months ago in reply to Albert Xu1

TI__Intellectual 840 points

Hi Albert,

We are considering SN74LV245A daisy chain up to 32 units to enable board scalability. When we think about bus cycle time of FPGA, the varitation becomes big issue

Could you give me any solution to achive short bus sycle time?
Could you provide us the varidation graph(x-axis: Tdis, y-axis: Percentage)? If only a few devices deviate form the typical value, it is possible to replace just thouse outlier devices after soldering.

Regards,
Hiromu

0 Hiromu Susami 3 months ago in reply to Hiromu Susami

TI__Intellectual 840 points

Hi Albert,

We are looking for low varitation delay logic of 244 and 245 family. Vcc=3.3.

Follwing devices seems nice. Are there recommended devices?

https://www.ti.com/product-category/logic-voltage-translation/buffers-drivers-transceivers/general-purpose-transceivers/products.html#1498=Catalog%3BAutomotive&1512=ALVC%3BAVC%3BLVT&0max=3.45%3B6&-1=245%3Bfalse&sort=1130;asc&

https://www.ti.com/product-category/logic-voltage-translation/buffers-drivers-transceivers/noninverting-buffers-drivers/products.html#1498=Catalog&1512=ALVC%3BLVT%3BAVC&0min=-0.5%3B3&0max=3.6%3B18&-1=244%3Bfalse&sort=1130;asc&

I think ALVC, LVT, AVC family is good for low varitation. Which family is the best for this time? I also wants to know the difference of these family.

Regards,
Hiromu

+1 Ian Graham 3 months ago in reply to Hiromu Susami

TI__Genius 12141 points

Hi Hiromu,

Any disclosure of details not in the datasheet typically requires an NDA, so we can't provide them here.

In terms of low variation, we would expect that the AVC family to have the lowest total variation because it is one of our fastest families.

Here's a comparison of the different logic families.

Logic

Logic forum

SN74LV245A: Delay time variation