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SN65HVD09: Design verification and all Single ended signal showing all high

Aarindom Basu
Prodigy 50 points
Part Number: SN65HVD09


Tool/software:

Hi,

This is the schematic I designed to make 8 channel TX and 8 channel RX Single ended to Differential and vice versa. While designing i thought it would work with 3V3 supply and later I shifted to 5V supply. When I fed serial pulses to the Singe ended side (U10) I did not see anything at Differential side instead i observed all the Single ended TX & RX lines are high. 

Can some one help to find out what would be the reason behind this abnormality?

-Ravi

  • 0
    Guru 317480 points

    As far as I can see, you have configured U10 according to figure 39, and U12 to figure 19.

    Please confirm the voltages at all control inputs.

    What are the voltages at the single-ended and differential pins of the channel you're testing?

    (For unidirectional connections, you do not need termination resistors at the drivers.)

  • 0 in reply to Clemens Ladisch
    Prodigy 50 points

    Configuration pins and Vcc are 5V. Single ended signals are 3.3V. 

  • 0 in reply to Aarindom Basu
    Prodigy 50 points

    Differential outputs are zero. 

  • 0 in reply to Aarindom Basu
    TI__Guru 74981 points

    Hi Aarindom,

    From a schematic check, I verified that the pinout of the device matches between the datasheet and the schematic. The you also have decoupling caps on all the Vcc pins which is also good. I assume you are using both device's Vcc at 5V based on your post. 

    Are you able to verify the voltages on the BSR, #CRE, CDE0, CDE1, CDE2 for both devices? From what I can see in the schematic you have several DNP resistors set up. 

    I suspect the issue may be related to these pins not being properly biased. If your trying to set U10 to be an RS422 driver (or RS485 full duplex driver) then using figure 39 in the datasheet to bias the pins would ne necessary as well as setting the correct correct bias on the DE/RE pins. (We should probably just focus on debugging the driver first then move onto the receiver after).

    If the biasing is correct, it may be possible that the device could of been soldered incorrectly or damaged. In which case, you may want to double check the soldering points or resolder the device. 

    -Bobby