• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 2 answers
  • Subscribers 33 subscribers
  • Views 338 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

THVD1406: About /SHDN pin

Hide
Guru 21045 points
Part Number: THVD1406
Other Parts Discussed in Thread: THVD1400,

Hi Team,

 

I understand that It is recommended that pull down /SHDN pin to GND through 10kohom.

However, our customer would like to pull up /SHDN pin to VCC=3.3V through 10kohm.

(So, they don’t need shutdown mode.)

Could you please let us know if you have any concern?

 

By the way, I found other thread.

Should I connect /SHDN pin directly to VCC?

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1177629/thvd1406-connection-of-re-shdn-pins

 

<Background >

They would like to use THVD1400 but can’t secure the quantity they need.

Therefore, they would like to use THVD1406 as above.

 

Regards,

Hide

  • 0
    Guru 244220 points

    It is not recommended to pull down /SHDN pin to GND. Where did you read that?

    You can pull it up to VCC directly or through 10 kΩ.

  • 0
    TI__Mastermind 43536 points

    Hi Hide,

    Pulling /SDN to VCC via a 10K resistor is fine - the /SDN pin is already tied internally to VCC via a 2MEG resistor - so you don't need to add anything since this pin is not floating - but the customer can.

    I wouldn't suggest pulling the /SDN pin to ground via a resistor as to keep the device operational you'd need to constantly be providing a voltage to this pin (if /SDN is used - for your application it isn't, but for reference /SDN should be connected to a GPIO of a controller or pulled to VCC (external pull-up is optional if unused). 

    Please let me know if you have any other questions.

    Best,

    Parker Dodson 

  • 0 in reply to Parker Dodson
    Guru 21045 points

    Hi Parker-san,

     

    Thank you for your response.

    By the way, red circle in Figure 9-5 is pull down for /SHDN pin.

    Is this a typo?

     

     

    Regards,

    Hide

  • +1 in reply to Hide
    TI__Mastermind 43536 points

    HI Hide,

    No it isn't a typo - I see where the confusion is coming from - I wasn't as clear about the /SHDN pin on my last reply.

    The Shutdown pin only shuts down the driver - so in this picture what you are seeing is that the driver is in shutdown mode when /RE is pulled low (active) so in RX mode the driver will be shutdown (low power). This is a special use case where /RE and /SHDN are shorted together (as many RS-485 applications short the control signals together - this is allowing a similar control scheme if using this device in that manner).

    If you don't need shutdown mode  (the device is being used in an auto-direction application) pulling the /SHDN pin high or leaving it open will be fine.

    Please let me know if you have any other questions!

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    Guru 21045 points

    Hi Parker-san,

    Thank you for the information.

    Regards,

    Hide