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Original question:

UCD3138: Two UCD3138 on one PMBus

UCD3138: 2 UCD3138 on the same PMBUS

LINDHEIMER Christophe
Prodigy 50 points
Part Number: UCD3138


Tool/software:

HI.

My hardware designer has put 2 UCD3138 on the same PMBUS.

I am in charge of the firmware design.

According to docs, in Romcode, @ for PMBUS is set at <0xB>

How can I flash the UCD when they are empty ?

If I try to flash, I guess that both UCD are going to ACK commands on PMBUS.

Does it mean that I will be able to flash the same firmware on both UCD ?

Thanks

  • 0
    TI__Genius 10465 points

    Hello Lindheimer,

    Thanks for waiting, July 4th was a US holiday.

    Please see the following E2E post: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/882440/ucd3138-two-ucd3138-on-one-pmbus 

    Yes, in ROM mode the address will always be 0d11 (0x0b). Thus, there may be issues communicating in ROM mode. In your code, you can set the a unique PMBus address for each UCD3138. After you flash the firmware onto the UCD3138s, the Fusion GUI will have a drop down that will allow you to select which UCD3138 you want to communicate with. See section 5 in the "UCD3138 - Responding to Multiple PMBus Slave Addresses": https://www.ti.com.cn/cn/lit/an/slua758/slua758.pdf.

    Regards,

    Jonathan Wong 

  • 0 in reply to Jonathan Wong
    Prodigy 50 points

    HI.

    I had aleady read your proposed thread but it does not answer clearly to my answer.

    Once MY firmware will be flashed, it will use the ADC to set a different address for each UCD. So, there will be no issue.

    My issue is how to deploy the first firmware, when both UCD will boot to romcode with @ 0xb.

    Ian Bower said "So in ROM mode you may have a problem. Some people report they can write programs to multiple devices."

    So, not very clear if I am going to have an issue...

    Thanks

  • 0 in reply to LINDHEIMER Christophe
    TI__Genius 10465 points

    Hello Lindheimer, 

    I will look into this issue further and provide a response tomorrow.

    Regards,

    Jonathan Wong

  • 0 in reply to Jonathan Wong
    TI__Genius 10465 points

    Hello Lindheimer,

    Apologies for the delay. E2E was down for maintenance from July 11 - 14. 

    Yes, the ROM mode is one limitation with the UCD3138 nonA and A variants. All current UCD3138x will have the same ROM mode address. So, it is unknown which one will respond if multiple UCD devices are tied to the same PMBus line. 

    This is a limitation that you will need to work around. For example, we have customers that do use multiple UCD3138x controllers. In production, they have methods where they are able to power on only one device at a time and flash the firmware onto each individual UCD3138x. You may need to adopt a similar strategy.

    The upcoming UCD3138R will not have this limitation in ROM mode. Please contact your local FAE for more exciting information on the UCD3138R.

    Regards,

    Jonathan Wong

  • 0 in reply to Jonathan Wong
    Prodigy 50 points

    Hi.

    Waiting for the real board, I made a test with two UCD3138HSFBEVM-029 Evaluation board.

    I have connected the two pmbus together.

    When I make a download from romcode, the two boards are flashed with the same firmware without issue.

    Then, my custom firmware attributes a different PMBUS address for each board (based on AD0 pin)

    Regards

    Chris