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ISO1541: TI/ISO1541DR communication fail of 400KHz

Marx Pan
Intellectual 305 points
Part Number: ISO1541

Dear TI member,

 

Nice to meet you. We use TI product TI/ISO1541DR and meet one issue.

Please refer below block diagram and information. Could you help us for this issue?

 

1.Set I2C_CLK to 100K Hz:The I2C address of AC power monitor IC can be recognized and the AC power monitor IC work normal.

2. Set I2C_CLK to 400K Hz(MCU):The I2C address of AC power monitor IC can be recognized but the AC power monitor IC can’t work.

I2C_CLK be set to 400K Hz(MCU):

(1)I2C_DATA can communication of TI/ISO1541DR so I2C address of AC power monitor IC can be recognized. (2)I2C_CLK can be transfer from SCL1 to SCL2 of TI/ISO1541DR so AC power monitor IC can’t work.

 

3.We did below check:

(1)MCU I2C can set to fast mode:400K Hz

(2)AC Power Monitor IC Interface:I2C and It can support 100K Hz and 400K Hz.

(3) The max operating frequency of TI/ISO1541DR can be 1M Hz

 

Block diagram:

Thank you.

  • 0
    Intellectual 305 points

    Sorry, correct information.

    I2C_CLK be set to 400K Hz(MCU):(2)I2C_CLK can’t be transfer from SCL1 to SCL2 of TI/ISO1541DR so AC power monitor IC can’t work.

  • 0 in reply to Marx Pan
    TI__Guru 52980 points

    Hi Marx,

    Sorry to hear about the issue and thank for sharing the details related to issue and the block diagram.

    Could you please share me the schematic showing both AC Power Monitor IC and MCU part numbers and their connections to ISO1541. In the block diagram, I do not see the pull-up resistors on MCU side but I believe you have those pull-up resistors in the schematic. Once you share these details, I will review the design to see if there are any obvious issues. Thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Intellectual 305 points

    Hi, Koteshwar,

    Yes, we pull-up in MCU side. Please refer below schematic.

    Please refer below for more detail.

    MCU: ST/STM32F303VET6, I2C EEPROM:MICROCHIP/24AA025E48T-I/OT, AC Power Monitor:MICROCHIP/MCP39F521T-E/MQ, ISOLATION: TI/ISO1541DR

    The I2C EEPROM can work normal whether the I2C_CLK is 100K Hz or 400K Hz.

    I2C connection:
    (1)MCU:PA9(I2C2_SCL),PA10(I2C2_SDA).

    (2)AC Power Monitor:Please refer below.

    Thank you so much.

  • 0 in reply to Marx Pan
    Guru 268890 points

    There are no obvious problems in the schematic.

    Please show oscilloscope traces of the working and non-working signals.

  • 0 in reply to Clemens Ladisch
    Intellectual 305 points

    Hi, Koteshwar,

    I checked with my member again.

    It seems that the I2C CLK can transfer of TI/ISO1541DR side1 and side2.

    Sorry to bother you and thanks for your help.

  • 0 in reply to Marx Pan
    TI__Guru 52980 points

    Hi Marx,

    No problem, thanks for confirming that the issue is resolved by customer and glad to know that. I will go ahead and mark this post resolved. Thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Intellectual 1770 points

    Hi Rao,

    Customer found that their host was stop data transmission with ISO1541.

    Input side waveform is strange, Data cannot recovery to high. But the output side waveform are normal.

    If customer remove this ISO1541, they won't see this issue. This issue won't show up when use 100k speed.

    Ch1: Clock from host ( SCL1)

    Ch2: DATA from host ( SDA1)

    Any suggestion?

  • 0 in reply to Shaquille Chen
    TI__Guru 52980 points

    Hi Shaquille,

    Sorry about the delayed response.
    Thanks for sharing the waveform. Could you please confirm that this waveform is related to the same application/customer that I was talking about with Marx?

    The bump in voltage from 0V to ~0.8V which you have highlighted with a red square is expected due to the bidirectional logic implemented in the device. Please refer to Section 8.4 and Figure 26 in ISO1541 datasheet for more details on this bump. This is usually not an issue as it doesn't affect communication or produce any errors.
    Its duration is dependent on the pull-up resistor and the load cap used on Side2 of ISO1541, could you please confirm these two for customer application? I see that the duration is approximately 3µs in the above application, can you please also confirm if this remains 3µs all the time you see such bump in waveform or if this 3µs happened only once and the usual time is lower? Thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Guru 52980 points

    Hi,

    This discussion has moved to private e-mails to look deeper into system and debug the issue. Once we reach a resolution, will come back and post an update with a summary. Thanks.

    Regards,
    Koteshwar Rao