• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 34 subscribers
  • Views 687 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

LMH0302

Aditya Mitra
Prodigy 50 points
Other Parts Discussed in Thread: LMH0302

We are using LMH0302 in our design. We have the following query :

  1. If input is HD but LMH0302 is configured as SD, will it damage the IC? (I understand that we will get a corrupted output due to selection of lesser bandwidth but my basic intent is to know whether IC gets damaged or not)
  2. Can LMH0302 accept SD when it is configured in HD? (when selected HD the internal drivers will be configured for higher bandwidth so it may be possible to accept SD which is of lower bandwidth.). What TI has to say on this?
  3. What is expected output in both the cases?
  4. What all does SD/HD pin configure internally in LMH0302? (other than bandwidth)
  5. If we disable the IC but our input source is still on (VCC and GND is applied but Enable pin is pulled low). Will It damage the IC?
  6. Our input source when put to standby mode pulls up both the input (SDI, SDI_n) high. Do you see any device specific issue when LMH0302 is in the following states and the input the input source is in standby mode.
  1. Power Gated
  2. IC Disabled (Enable Pin Low)
  3. IC ON (Enable Pin High)

Regards
Aditya
  • 0
    TI__Genius 13475 points

    If input is HD but LMH0302 is configured as SD, will it damage the IC? (I understand that we will get a corrupted output due to selection of lesser bandwidth but my basic intent is to know whether IC gets damaged or not)

    The device will not be damaged, all that the SD/HD control does is to change the slew rate on the outputs since SMPTE 259 (SD) specifies a slower edge rate than the slowest specified by SMPTE 292 or SMPTE 424 (HD and 3G specs)

    Can LMH0302 accept SD when it is configured in HD? (when selected HD the internal drivers will be configured for higher bandwidth so it may be possible to accept SD which is of lower bandwidth.). What TI has to say on this?

    The device will operate normally with an SD input and configured in HD, but the slew rates of the outputs will be faster than the maximum allowed slew rate in SMPTE 259 so the output will not be compliant with video specs.

    What is expected output in both the cases?

    If an SD signal is applied in HD mode, the output will have faster edges than allowed by the SD-SDI spec.  If an HD signal is applied in SD mode, the output will have slower edges than allowed by the HD-SDI spec.

    What all does SD/HD pin configure internally in LMH0302? (other than bandwidth)

    Only the slew rate of the output.

    If we disable the IC but our input source is still on (VCC and GND is applied but Enable pin is pulled low). Will It damage the IC?

    No

    Our input source when put to standby mode pulls up both the input (SDI, SDI_n) high. Do you see any device specific issue when LMH0302 is in the following states and the input the input source is in standby mode.

    As long as the inputs are not pulled above Vdd for the LMH0302, there should be no issue.

    If the power gating results in a low impedance source and SDI and SDI_n are high, then it is possible that they will turn on the ESD protection diodes, if not current limited, then this could present a problem.   If the device is enabled or disabled via the Enable pin, there should be no ill effects.

  • 0 in reply to Mark Sauerwald88474
    Prodigy 50 points

    Mark Sauerwald 

    Thanks for the reply :)

    One more thing I wanted to ask is -  Can we change the configuration from SD to HD and vice versa in run time or we have to disable LMH0302 first and then change the configuration.

    Regards

    Aditya

  • 0 in reply to Aditya Mitra
    TI__Genius 13475 points

    HD/SD can be switched any time that you desire, LMH0302 does not need to be disabled.

  • 0 in reply to Mark Sauerwald88474
    Prodigy 50 points

    "Can LMH0302 accept SD when it is configured in HD? (when selected HD the internal drivers will be configured for higher bandwidth so it may be possible to accept SD which is of lower bandwidth.). What TI has to say on this?

    The device will operate normally with an SD input and configured in HD, but the slew rates of the outputs will be faster than the maximum allowed slew rate in SMPTE 259 so the output will not be compliant with video specs."

    We tested it in our boards. When we give a color bar input in SD and we configured LMH0302 in HD, output was perfect. I think this experiment can be carried out at your end too to confirm the same.

    Regards

    Aditya