DS90UB947-Q1: Timing requirements for 947 and 948 matching

zhijian Mao

Part Number: DS90UB947-Q1
Other Parts Discussed in Thread: ALP

Hi, Ti

Currently our circuits are used when 947 and 948 are matched, However, the LOCK of the 948 is unstable and does not lock well, and the register configuration of the 948 cannot be written.

Considering that it may be caused by timing, what is their correct timing?

The timing we have set so far is as follows:

947 Power on→Pull up the PDB of the 947→948 Power on→Pull up the PDB of the 948→Configure the 947→Configure the 948

Is this timing correct?What is the correct time interval for each？

over 3 years ago

0 Logan Cummins over 3 years ago

TI__Guru 66840 points

Hi Zhijian,

Please see the Recommended Power-Up Sequence diagram and table in the 947 and 948 datasheets for the required timings for power rails, PDB, and device to device interval times.

Let me know if you have any additional questions, and if still experience issues; then post power-up waveforms of both 947 and 948's VDD and PDB rails.

Regards,

Logan

0 zhijian Mao over 3 years ago in reply to Logan Cummins

Prodigy 130 points

Hi，Logan

Ask another question：

If the link of 947 and 948 is OK, but the PDB has not been pulled high, will the register of 947 and 948 be configured successfully?

0 Logan Cummins over 3 years ago in reply to zhijian Mao

TI__Guru 66840 points

Hi,

PDB going high is what enables the device. The device must be enabled prior to register configuration of 947 and lock with 948.

Regards,

Logan

0 zhijian Mao over 3 years ago in reply to Logan Cummins

Prodigy 130 points

Hi，Logan

At present, our circuit, the LOCK of the 948 is unstable, similar to the PWM waveform, the register of the 948 configured by the 947 often fails, and the screen of the display is shaking badly, do you think what is the cause of this?

FPD-LINK mode is coax mode,

947 MODE_SEL0 : #5; MODE_SEL1: #6

948 MODE_SEL0 : #5; MODE_SEL1: #2

0 Logan Cummins over 3 years ago in reply to zhijian Mao

TI__Guru 66840 points

Hi Zhijian,

Can you provide MAP analysis tool results in the ALP software? Can you also provide schematic?

Regards,

Logan

0 zhijian Mao over 3 years ago in reply to Logan Cummins

Prodigy 130 points

Hi，Logan

The oscilloscope image is the LOCK signal of the 948，The R1045 for the 948 has been changed to 4.7k

5706.pdf

947.pdf

0 Logan Cummins over 3 years ago in reply to zhijian Mao

TI__Guru 66840 points

Hi Zhijian,

The lock signal appears to be intermittent/marginal. Please provide the MAP analysis tool results from the ALP software: https://www.ti.com/lit/pdf/snlu243

This will give us a better idea how marginal the link is.

Regards,

Logan

0 zhijian Mao over 3 years ago in reply to Logan Cummins

Prodigy 130 points

Hi，Logan

There are examples of register configurations for the 947 and 948 using coaxial mode.

0 Logan Cummins over 3 years ago in reply to zhijian Mao

TI__Guru 66840 points

Hi Zhijian,

zhijian Mao said:
There are examples of register configurations for the 947 and 948 using coaxial mode.

What exactly is your question? Are you able to provide the MAP analysis tool results from the ALP software?

Regards,

Logan

0 zhijian Mao over 3 years ago in reply to Logan Cummins

Prodigy 130 points

Hi，Logan

The problem has been solved, it is a matter of timing

Interface

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DS90UB947-Q1: Timing requirements for 947 and 948 matching