SN74LVT244B: Is there any problem to use SN74LVT244B like SN74LS243 by external connection?

Kazuya Nakai59

Guru 21645 points

Part Number: SN74LVT244B
Other Parts Discussed in Thread: SN74LS243,

Hello guys,

One of my customers wants same function device in SN74LVT series as SN74LS243.

SN74LS243

QUADRUPLE BUS TRANSCEIVERS

http://www.ti.com/jp/lit/ds/symlink/sn74ls243.pdf

The customer couldn't such function (4bit tranceiver IC) in LVT series.

So they are considering using SN74LVT244B with external connecting 1Yn to 2An,

and connecting 2Yn to 1An.

Their questions are the followings.

Q1. Is there any problem to use SN74LVT244B like SN74LS243 by external connection like the above?

Q2. Do you have any 4bit tranceiver IC in LVT series?

Your reply would be much appreciated.

Best regards,

Kazuya.

over 5 years ago

0 Dylan Hubbard over 5 years ago

TI__Mastermind 46045 points

Hi Kazuya,

There isn't a way to configure the SN74LVT244B to work the same as SN74LS243. If they want a LVT transceiver they will have to go with an octal option.

0 Kazuya Nakai59 over 5 years ago in reply to Dylan Hubbard

Guru 21645 points

Hi Dylan,

Thank you for your reply.

Shmitt trigger function is not needed for the customer.

1OE/2OE active level is not concerned.

They think SN74LVT224B can be used as a 4bit bus transistor with the following conection.

1. Connect 1A1 to 2Y1.

2. Connect 1Y1 to 2A1. 1+2= for No.1 of bus tranceiver.

3. Connect 1A2 to 2Y2.

4. Connect 1Y2 to 2A2. 3+4= for No.2 of bus tranceiver.

5. Connect 1A3 to 2Y3.

6. Connect 1Y3 to 2A3. 5+6= for No.3 of bus tranceiver.

7. Connect 1A4 to 2Y4.

8. Connect 1Y4 to 2A4. 7+8= for No.4 of bus tranceiver.

Is their thinking wrong?

Are these connections wrong for 4 bit bus tranceivers?

Could you please tell me what problem is in this connection (solution)?

Thank you again and best regards,

Kazuya.

0 Clemens Ladisch over 5 years ago in reply to Kazuya Nakai59

Guru 317370 points

This would work. It would result in the same circuit as in a standard transceiver, but you have to control the OEs in a different way.

0 Dylan Hubbard over 5 years ago in reply to Clemens Ladisch

TI__Mastermind 46045 points

Hi Kazuya,

Sorry I was talking in terms of functionality. The buffer won't allow you to dynamically change directions of each channel, but also there will bus contention on every transition due to propagation delay if you configure it this way. Also I'd take caution with the OE pins as to not cause any of the inputs to be floating if they plan on utilizing inputs.

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SN74LVT244B: Is there any problem to use SN74LVT244B like SN74LS243 by external connection?