LMH1218: SDI Cable Driver

Kazuki Itoh

Part Number: LMH1218
Other Parts Discussed in Thread: DIT4192

Tool/software:

Hi team,

My customer is designing a board with LMH1218.

Could you please let me know if there is any risk of damage to the device if the SDI BNC output are accidentally connected to each other?

Best regards,

Kazuki Itoh

9 months ago

0 Drew Miller1 9 months ago

TI__Mastermind 37623 points

Hi Itoh-san,

We're looking into this and will get back to you early next week.

Thanks,

Drew

+1 Nick Peabody 9 months ago

TI__Genius 9209 points

Hi Kazukh,

I do not think there is a risk to damaging the part by connecting the outputs. But note that there is no benefit to connecting them together because it corrupts the output data.

Best Regards,

Nick

0 Kazuki Itoh 9 months ago in reply to Nick Peabody

TI__Genius 11000 points

Hi Nick-san,

Could you let me know the technical reason behind your comment?

For instance, is there coupling cap inside? Or, does the device have protection circuit in the driver?

Best regards,

Kazuki Itoh

+1 Nick Peabody 9 months ago in reply to Kazuki Itoh

TI__Genius 9209 points

Hi Kazuki-san,

There is no protection circuit in the device. Does the short occur before or after the AC coupling caps or after a cable?

Have you observed any issues or degradation in the data output after shorting the outputs?

Best Regards,

Nick

0 Kazuki Itoh 9 months ago in reply to Nick Peabody

TI__Genius 11000 points

Hi Nick-san,

It is assumed that users do the mis-wiring after the ac-coupling cap.
It is not assumed that the output pins are directly connected each other after implementing the driver to the PCB.

Best regards,
Kazuki Itoh

0 Nick Peabody 9 months ago in reply to Kazuki Itoh

TI__Genius 9209 points

Hi Kazuki-san,

OK, that is acceptable. There would be no problems because the resulting swing would be 0 V. The + and - differential signals would cancel each other out.

Best Regards,

Nick

0 Kazuki Itoh 9 months ago in reply to Nick Peabody

TI__Genius 11000 points

Hi Nick-san,

Sorry for the additional question.
Could you provide ESD protection circuit example for this device (both for driver and equalizer)?

Best regards,
Kazuki Itoh

0 Nick Peabody 9 months ago in reply to Kazuki Itoh

TI__Genius 9209 points

Hi,

I'll ask a designer about this question.

Best Regards,

Nick

0 Nick Peabody 9 months ago in reply to Nick Peabody

TI__Genius 9209 points

Hi Kazuki-san,

SDI is CML with 75 ohm impedance. It has a low capacitance ESD protection with two diodes connected from the signal pin to VCC and GND. The ESD diode turns on if the data line is higher than VCC or lower than GND.

Best Regards,

Nick

0 Kazuki Itoh 9 months ago in reply to Nick Peabody

TI__Genius 11000 points

Hi Nick-san,

Thank you for your response.

When using the SRC in the bypass mode and the configuration is like below;

AES input -> SRC (Bypass mode) -> AES output.

Does the AES driver arbitrarily generate the AES output frame?

DIT4192 is implemented. Is it possible to point assign the top of the frame from external pin?

Best regards,
Kazuki Itoh

0 David (ASIC) Liu 9 months ago in reply to Kazuki Itoh

TI__Guru**** 180061 points

Itoh-san

Are you asking the AES question for DIT4192 or LMH1218?

Thanks

David

0 Kazuki Itoh 9 months ago in reply to David (ASIC) Liu

TI__Genius 11000 points

Hi David-san,

My customer is referring to DIT4192 AES driver.

Best regards,

Kazuki Itoh

0 David (ASIC) Liu 9 months ago in reply to Kazuki Itoh

TI__Guru**** 180061 points

Itoh-san

I forwarded your question to our audio group for the support on DIT4192 AES driver.

Thanks

David

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LMH1218: SDI Cable Driver