SN74LVC8T245: Question about VCCA and signal inputs

Austin Do

Part Number: SN74LVC8T245
Other Parts Discussed in Thread: SN74LV541AT, CD74ACT541, SN74AHCT541, , SN74AHCT245, SN74ACT245, SN74LVCC3245A

Hello team,

My customer wants to design two use-cases with one schematic.

Is it possible to use below two cases with VCCA: 5V / VCCB: 5V?

In datasheet, V_IH is 0.7*VCCA, so it is difficult to use for 3.3 input. Is it right?

The first case:

The second case:

Best Regards,

Austin

over 2 years ago

+1 Clemens Ladisch over 2 years ago

Guru 281000 points

To be able to handle 3.3 V input signals with a 5 V supply, you need a device with TTL-compatible inputs, e.g., SN74AHCT541, SN74LV541AT, or CD74ACT541.

0 Austin Do over 2 years ago in reply to Clemens Ladisch

TI__Intellectual 2375 points

Hi Clemens,

Well noted. Thanks for reply.

PCB re-design is very limited from customer. I'll ask the customer to use different power supply for each use-case.

Best Regards,

Austin

+1 Clemens Ladisch over 2 years ago in reply to Austin Do

Guru 281000 points

The SN74LVC8T245 pinout is compatible with single-supply transceivers like the SN74AHCT245/SN74ACT245. (Please note that the pinout shown is wrong; pin 23 also is V_CCB, and is the only supply for the plain transceiver.)

0 Austin Do over 2 years ago in reply to Clemens Ladisch

TI__Intellectual 2375 points

Yes, the pictures are not SN74LVC8T245. I took a snap with wrong part(may be SN74LVCC3245A)..

Compatible with SN74AHCT245 is meaning that only use 20 pins from the current PCB like below?

Best Regards,

Austin

+1 Clemens Ladisch over 2 years ago in reply to Austin Do

Guru 281000 points

Yes.

Logic

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SN74LVC8T245: Question about VCCA and signal inputs