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SN74HC595B, question about exposed pad, maximum frequency and pin connection for not using pin.

Shinichi Inoue
Guru 20896 points
Other Parts Discussed in Thread: SN74HC595B

Dear Specialists,

My customer is designing SN74HC595B, and he has some questions.

Could you please advise them.

(1) where should be connected? The datasheet is not described.

Generally, exposed pad is connect to GND.

How is this device? Can he consider similarly?

(2) What is the maxmum frequency at 3.3V supply?

The datadheet say only 2.5V, 4V and 6V, not 3.3V

My image, should he be calculated by 5MHz@2.5V and 25MHz@4V.

In this case, 15.23MHz@3.3V, is it correct?

(3)connection for not using pin, OE, Qh' and SRCLR.

Are they correct for not using 

OE：GND directly connect

Qh'：OPEN

SRCLR：3.3V directly connect

I appreciate your great help.

Best regards,

Shinichi

  • 0
    TI__Guru 59460 points
    Hi Shinichi ,

    1) The exposed thermal pad must be connected to gnd for best thermal and mechanical performance. I had put in request to update the datasheet regarding the same. The package addendum in the datasheet has the footnote about the exposed thermal pad as well.
    2) The linear interpolation to determine the freq is what I will suggest to get the estimate freq value.
    3) Yes , the direct connection as you suggested is good.
  • 0 in reply to ShreyasRao
    Guru 20896 points
    Dear Shreyas

    Thank you for your reply.

    I am going to send your answer to the customer.

    I appreciate your great help.

    Best regards,
    Shinichi