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DDC114: DDC114 output data shifting problem.

Kazuya Nakai59
Guru 20060 points
Part Number: DDC114

 Hello guys,


 One of our customers observed an output data shift on DDC114.

Could you please help on the following questions?

 

-Questions

    1. When a CONV signal is shorter than minimum value or longer than maximum value, how behave the DDC114?

(If it’s undesirable for DDC114, customer wants to take measures.)

    1. Have you seen that an order of outputs data has been shifted in normal operation?

 

-Background

 

In the normal operation, the order of digital data output of both Side A and Side B are follows.

Input4->Input3->Input2->Input1

 

However, customer observed following order shift.

Input2->Input1->Input4->Input3

 

Once the output order is shifted, it keeps the order until power off/on.

 

Customer tried to reproduce this phenomenon, but they didn’t succeed. They observed it just once in debugging.

Customer will restart the reproduce test next week.

 

 

-Condition

A microcomputer controls CONV width adjustably from 333.3us(min). Basically, the DDC114 always operate for measurement.

 

While it is powered on, it sometimes software reset only the microcomputer asynchronously with the state of the DDC 114.

In that case, the control signal(MCU pin) to the DDC114 is initialized. As a result, CONV signal sometimes shorter or longer than the datasheet spec.

Customer concerns whether the CONV signal(longer or shorter than d/s spec) affects to the OUTPU order shift.

 

-Pin setting

OUTPUT format : 20bit (FORMAT = 1)

Mode : High speed (HISPD/LOPWR = 1)

Master clock : x1 (CLK_4X = 0),  Appling 4.8MHz.

 

 Your reply would be appreciated.

 Best regards,

 Kazuya Nakai.

  • 0
    TI__Mastermind 49146 points
    Hello Kazuya,

    We have not encountered a situation where the order of the output data is shifted in normal operation.
    Can you let us know the range setting as well?
    Also what was the pulse duration of the CONV signal when the customer observed the data order shift?
  • 0 in reply to Praveen Aroul
    Guru 20060 points
    Hello Praveen Aroul,

    Thank you for your reply. I asked the customer to give us information of the range setting and CONV duration. But they are busy now to preparing mass production line of the products which uses DDC114. They said that they would give us the information around the end of September.
    So I will inform you their feed back when I get it.

    Also they have a additional question as the follow. Could you please give us your answer for DDC114?

    Question.
    DDC114 digital input control signals are controlled by a micro controller. And DDC114 and the controller are reset by same reset signal. So the DDC114 digital control signals are floating until the controller ports connected to DDC114 digital input are defined to output mode.
    In this case, does DDC114 have any problems? Does DDC114 go back to normal operation after digital input are set from floating to H or L level?

    Your reply would be much appreciated.

    Thank you again and best regards,
    Kazuya Nakai.
  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 49146 points
    Hello Kazuya,

    It is recommended to keep the digital control lines low after power up and atleast 50 us after reset is released.
    With the digital input floating, the operation of the state machine could be unpredictable.
    Even if we test this condition on an evaluation module and the device seems to be functional, it does not guarantee for every device.

    Our recommendation is to isolate the reset signal of the microcontroller and the DDC114 and control the RESET of the DDC114 using the microcontroller GPIO pin or possibly have a weak pulldown on the CLK and CONV pins. Both of these would require some hardware modifications.

    Can you provide more details about your customer? Please send me an email at praveen.aroul@ti.com if you would like to take the conversation offline.
  • 0 in reply to Praveen Aroul
    Guru 20060 points
    Hello Aroul,

    I got the cusomer shematic around DDC114 and I will send it to your mail address (praveen.aroul@ti.com).
    So could you please check whether the schematic has problem or not?

    Thank you and best regards,
    Kazuya Nakai.
  • 0 in reply to Kazuya Nakai59
    Guru 20060 points
    Hello Aroul,

    Thank you for your support by off line.
    Today the customer told us that please close this support because this problem may be rare case.
    If the problem happens again, they will tell us again and I will consult with you then.

    Thank you again and best regards,
    Kazuya Nakai.