• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 32 subscribers
  • Views 1017 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.

SN65LVDS1: Using SN65LVDS1/SN65LVDS2 with DS90LV017A/DS90LV018A causing blown devices

Jeff Ross
Prodigy 90 points
Part Number: SN65LVDS1
Other Parts Discussed in Thread: DS90LV017A, SN65LVDS2, DS90LV018A,

We have 2 circuit boards that need to communicate over an external LVDS cabled interface. The interface is a basically a master/slave SPI bus using the LVDS drivers/receivers for the 'cables' part of the interface. One of the boards uses the DS90LV017A/DS90LV018A devices and the other board uses  SN65LVDS1/SN65LVDS2 devices.

In certain circumstances, all of the DS90LV017A/DS90LV018A components on the 'master' board will get blown. In the blown condition, the devices get very hot in circuit, removing them from the board I find that the VCC pin is shorted to GND at about 10 ohms.

The boards are each separating powered and can be powered up in any order. Is there some sort of latch-up condition occurring?

  • 0
    TI__Mastermind 43795 points

    There is likely a voltage difference between the boards at power up or when the cabling between the boards is connected.  Is there any ESD protection diodes at the connector?  The diodes could help to limit the voltage and current applied through the LVDS IO.

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Prodigy 90 points
    I’ve tried powering both boards from a single power supply to eliminate the ground offset. While this did improve the problem significantly, we’re starting to have other occurrences of blown devices.

    The blown devices are always the DS90LV017A/DS90LV018A components and never the SN65LVDS1/SN65LVDS2 devices.
    The cable is plugged in before power is applied to either board.
    We do not have ESD protection at either connectors.

    We have multiple other boards that also use this interface, mostly all using the DS90LV017A/DS90LV018A components on both sides of the cable.
    It’s just this one board with SN65LVDS1/SN65LVDS2 devices that has brought forth this issue.
  • 0 in reply to Jeff Ross
    TI__Mastermind 43795 points

    Hi Jeff

    I would expect no issues powering from the same supply.

    Have you tried to probe the interface during the power ramp?

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Prodigy 90 points

    Oh if only it was that easy...

    Attaching the ground lead from the scope probe changes the behavior up to and including not blowing the devices.

    I know that is a 'clue', however it's a head-scratcher one that doesn't seem to make sense.

    I've even had an occurrence where the DS90LV017A/DS90LV018A components all blew on the 'master' board when attached/cabled to the 'slave' board and the 'slave' board was connected to the common power supply, but the toggle switch for power was off (blocking main power but not ground).

    I'm at wit's end on this one, (way past wit's end actually) and am leaning toward some compatibly issues between these two different families of LVDS components.