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DSLVDS1047: Can unused input pin be left open?

Kazuya Nakai59
Guru 20650 points
Part Number: DSLVDS1047
Other Parts Discussed in Thread: DSLVDS1048

Tool/software:

Hello guys,

One of my customers uses DS90LV031ATM/NOPB and DS90LV032ATM/NOPB for their current products.

They are considering replacing DS90LV031ATM/NOPB with DSLVDS1047.
At this moment, they have the following questions.
Could you please give me your reply?

Q1.
DSLVDS1047 datasheet says on page 13 that "Open Input Pins. The DSLVDS1048 is a quad receiver device,
and if an application requires only 1, 2, or 3 receivers, the unused channel(s) inputs must be left OPEN.
Do not tie unused receiver inputs to ground or any other voltages."

I think DSLVDS1048 in this sentence is incorrect and the correct sentence is that the DSLVDS1047 is a quad receiver device...
Is my thought correct?

Q2.
This is just confirming. If DSLVDS1047 has no used pin at DIN1~4, must the pin be left OPEN?

Q3.
Is there any problem at DSLVDS1047 and DS90LV032ATM/NOPB combination?

Your reply would be much appreciated.

Best regards,
Kazuya.

  • 0
    Guru 271610 points

    1. Section 8.3.1 talks about the receiver. It was accidentally copied into the driver datasheet.

    2. The driver's input pins must not be left floating. If not used, connect them to VCC or GND.

    3. All LVDS drivers are compatible with all LVDS receivers.

  • 0
    TI__Genius 13281 points

    Hello,

    I have been out of office and I will get back to you this week.

    Thank you, Amy

  • 0 in reply to Amy
    Guru 20650 points

    Hello Amy,

    Thank you very much for your reply.

    I see. I will wait for your next reply.

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Genius 13281 points

    Hello Kazuya,

    Q1 - correct, like this was copied from the receiver datasheet. This is a typo.

    Q2 - per the datasheet, "The DSLVDS1048 is a quad receiver device, and if an application requires only 1, 2, or 3 receivers, the unused channel(s) inputs must be left OPEN. Do not tie unused receiver inputs to ground or any other voltages. The input is biased by internal high value pullup and pulldown resistors to set the output to a HIGH state. This internal circuitry ensures a HIGH, stable output state for open inputs"

    Q3 - correct, these devices can pair together (LVDS out -> LVDS in) 

    Regards, Amy

  • 0 in reply to Amy
    Guru 20650 points

    Hello Amy,

    Thank you very much for your reply.

    About Q2, they want to know how to treat DINx of DSLVDS1047 no used channel.
    Is it to connect the input pin (DINx) of no used channel to GND or VCC directly as Clemens said?

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Genius 13281 points

    Hello,

    I see your question. This section in the datasheet is a bit confusing. It is trying to help the reader understand the ways to pair the DSLVDS1047 transmitter with the DSLVDS1048 receiver. The recommendation per Q2 should be followed if using the DSLVDS1048 receiver. For the transmitter inputs, the output will be determined by the Table 1. Truth Table if tied high, low, or no connect (indeterminate output), and if the DSLVDS1048 receiver is used this should be left open.

    Thanks, Amy

  • 0 in reply to Amy
    Guru 20650 points

    Hello Amy,

    The customer doesn't use one of 4ch drivers of DSLVDS1047.
    They would like to know how to handle the input pin (DINx) of the unused channels of the DSLVDS1047.
    As Clemens said in this thread, is the input pins of the unused channels needed to connected to GND or VCC directly?

    Thank you very much and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Genius 13281 points

    Hi Kazuya,

    The datasheet does not have specific recommendations for unused inputs, but it is best practice to ensure the signal is in a known state (i.e., per Table 1 Truth Table, so tying to GND or VCC). 

    Regards, Amy