SN74CB3Q3345: Is it possible to use 1pin(OE) pin left open

Shinichi Inoue

Guru 21721 points

Part Number: SN74CB3Q3345
Other Parts Discussed in Thread: SN74CB3T3245, SN74CB3Q3245

Dear Specialists,

My customer is considering SN74CB3345 instead of SN74CB3245.

They have a question about OE pin.

I would be grateful if you could advise.

---question

We are considering SN74CB3Q3345 as a replacement for SN74CB3T3245.

The SN74CB3T3245 and SN74CB3Q3345 differ in the function of pin1.

Current: SN74CB3T3245DGVR 1pin function: NC
Substitute: SN74CB3Q3345DGVR 1pin Function: OE

When the SN74CB3Q3345DGVR pin 19: OE~ pin is connected to GND, is it possible to use pin 1: OE pin left open?

In addition, 1pin: Is OE terminal internally pulled up or pulled down?

Bus Switch is fixed to ON state.

---

I appreciate your great help in advance.

Best regards,

Shinichi

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 317450 points

If you leave pin 1 open, it floats, which is forbidden: [FAQ] How does a slow or floating input affect a CMOS device?

OE must be connected to V_CC.

+1 Bryan Marshall over 3 years ago

TI__Genius 10974 points

Hello,

The SN74CB3Q3345 cannot be used as a direct replacement for the SN74CB3T3245 as the CB3T device acts as a voltage translator and the CB3Q does not ( this is a traditional signal switch). If you do not need voltage translation, you can look into the SN74CB3Q3245 which is has the same pinout as the SN74CB3T3245 with only a single OE pin.

Lastly, for any logic pin, it is advised to never leave those types of pins floating on our devices as they can be in an indeterminate state and may switch inadvertently depending on the environment they are in.

Thanks!

Bryan

0 Shinichi Inoue over 3 years ago in reply to Bryan Marshall

Guru 21721 points

Hi Bryan,

Thank you for your reply.

I understand SN74CB3Q3345 doesn't have voltage translate function.

Also when the customer doesn't need this function, SN74CB3Q3245 is recommended.

I'll share these information with the customer.

When the customer have an additional question, I consult you again.

I appreciate your great help and cooperation.

Best regards,

Shinichi

+1 Bryan Marshall over 3 years ago in reply to Shinichi Inoue

TI__Genius 10974 points

Sure thing, let me know if there is anything else I can do to help out here.

Thanks!

Bryan

0 Shinichi Inoue over 3 years ago in reply to Bryan Marshall

Guru 21721 points

Hi Bryan,

The customer understood your suggestion.

Let's close this thread.

I appreciate your great help and cooperation.

Best regards,

Shinichi

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SN74CB3Q3345: Is it possible to use 1pin(OE) pin left open