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DS90UB940N-Q1: Difference in power-on timing between 940 and 940N

Alan Xia
Genius 11500 points

Part Number: DS90UB940N-Q1

Hi Team，

Tier1：Neusoft

OEM: Geely

We found that there are differences in the power-on timing of 940 and 940N. What is the reason for the change?

940：

940N：

What is the second PDB pull-up of 940N? Why was this change made?

Because the customer may have no waveform output in the 940 mipi csi data lane (2 data lanes are used), which will lead to no image problem. After inspection, it was found that they were using 940N, but the timing was done with reference to 940, and then after changing to the power-on timing required by 940N, the problem disappeared. Customers want to know what the root cause is?

  • 0
    TI__Mastermind 25765 points

    Hi Alan,

    The power up sequence you have posted for the 940 is not the most up to date datasheet. The power sequence for both of these devices are the same. Please refer to the most recent version of the datasheet which is on ti.com (revised 2020): SNLS479B

    Regards,

    Ben

  • 0 in reply to Ben Dattilo
    TI__Genius 11500 points

    Hi Ben，

    OK，but the customer want to know why 940‘s power sequence have this change？

    They find that 940n/960/962 all need to pull PDB twice. Can you help to explain why these devices need to do this action in detail?

    Tier 1 need to explain to OEM.

  • 0 in reply to Alan Xia
    TI__Mastermind 25765 points

    Hi Alan,

    This power up sequence does not show a requirement to toggle PDB twice. t4 shows the pulse width of PDB when there is a hard digital reset (not a part of start up requirements).

    Regards,

    Ben

  • 0 in reply to Ben Dattilo
    TI__Genius 11500 points

    Hi Ben，

    It seems you still haven't responded to my question.
    1. What the customer wants to know is why there is this drop-down in the T4 stage. What is the main purpose of this drop-down?
    2. What is the internal working mechanism of the chip?
    3. Is it to avoid some problems in initial configuration?

  • 0 in reply to Alan Xia
    TI__Mastermind 25765 points

    Hi Alan,

    My previous response is in reference to this. This figure is not showing a requirement to toggle PDB twice. Please refer to the table below this graph. This second toggle is simply a visual representation of what happens when a hard digital reset is issued to the device:

    Regards,

    Ben