DS92LV2411 de-emphsis

toshi-e2e

Other Parts Discussed in Thread: DS92LV2412, DS92LV2411

Hi all,
My customer is facing a problem that the Dout wave form has the strong de-emphasis level even if the de-emph pin is open. And the deserializer of DS92LV2412 cannot lock sometimes.

DS92LV2411 Configurations;

De-emph: open
VODSEL: open
SCL & SDA: open
CLKIN: 20MHz

Also, my customer measured the voltage of the De-emph pin as follows;Is this result normal?

R            Voltage of De-emph pin
----------     ----------------------------
open         1.25V
5.1kΩ        0.90V
2.0kΩ        0.64V
1.4kΩ    0.54V

Regards,
Toshi

over 10 years ago

0 Nasser Mohammadi over 10 years ago

TI__Guru* 93670 points

Toshi-San,

When you are in this mode, could you please activate PDB, logic 0, and then release this pin(logic 1)? This will re-initializes the device while different power supplies are stable.

Regards,,nasser

0 toshi-e2e over 10 years ago in reply to Nasser Mohammadi

Genius 4830 points

Nasser-san,

Thanks for your response.

The PDB is keeping the low level about 250ms after 3.3V and 1.8V is ON.
Does the PDB need to set logic 0 again?

Regards,
Toshi

0 Michael Lu (Santa Clara) over 10 years ago in reply to toshi-e2e

TI__Mastermind 29655 points

Hi Toshi-san,

Yes, toggle the PDB low and high again while the device is powered on (3.3V and 1.8V supplies should be high the entire time). It looks like from your waveforms that PDB is going from low to high in a reasonable amount of time after VDD has setlled (>1.5 ms afterwards).

In addition to Nasser's recommendation, is it possible to disable de-emphasis by setting Reg 0x02[4] = 1 in the serializer I2C?

Thanks,

Michael

0 toshi-e2e over 10 years ago in reply to Michael Lu (Santa Clara)

Genius 4830 points

Hi Michael-san,

Customer cannot disable de-emphasis by setting register in the serializer I2C because there is no pattern for connecting I2C signals on their own designed board.

Also, customer tried to toggle the PDB after power up. But the result was the same as before.

Anyway, could you please share the output waveform with 20MHz of CLKIN?

Regards,
Toshi

0 toshi-e2e over 10 years ago in reply to toshi-e2e

Genius 4830 points

Hi Nasser-san and Michael-san,
Thanks for your kind support for this problem.

Customers found that there was a problem with the differential probe for measurement.
They confirmed that DS92LV2411 operated correctly by using a single-end probe.
So, I would like to close this issue.

I am sorry to spend wasted time on you.

Best regards,
Toshi

0 Michael Lu (Santa Clara) over 10 years ago in reply to toshi-e2e

TI__Mastermind 29655 points

Hi Toshi-san,

Thanks for helping to close this issue, and appreciate your feedback!

Michael

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DS92LV2411 de-emphsis