• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 3 answers
  • Subscribers 65 subscribers
  • Views 369 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UC3907: UC3907

willie mccain
Prodigy 175 points
Part Number: UC3907
Other Parts Discussed in Thread: UCC29002

Okay

On the master indicator

I have three unit on the share bus

PS1 PS2 PS3

SO PS1 IS THE MASTER PS2 AND PS3 INDICATORS ARE OFF.

LETS SAY PS1 FAILS AND THE NEW MASTER SWITCHES TO PS2 SO I POWER DOWN PS1 PULL IT OUT AND REPLACE THE UNIT AFTER THE INSTALL POWER THE SUPPLY UP . NOW PS2 IS STILL THE MASTER HOW WOULD YOU TOGGLE THE UNITS TO SWITCH THRU PS1 PS2 AND PS3 SO YOU CAN SELECT ANY UNIT TO BE THE MASTER. WHAT DO I NEED TO DO TO HAVE CONTROL ON WHICH UNIT IS THE MASTER AFTER ANY UNIT FAILURE.

NOW ALSO I SEE THAT I WILL NEED THREE LINES FROM THE UC3907 TO BE JUMPERED TOGETHER FOR NORMAL SYSTEM OPERATION OF MULTIPLE UNITS ON THE BUS.

ALSO WHAT IS THE NUMBER OF UNITS THAT CAN BE PARRALLED ON THE SYSTEM BUS

AND IF I NEED MORE UNITS TO BE ON THE BUS WHAT WILL I NEED TO DO TO INCREASE THE NUMBER OF UNITS PARALLED.

THANKS

WILLIE L. MCCAIN

  • 0
    TI__Guru* 86266 points

    Hello,

    We have assigned and applications engineer to look into this for you and they will be getting back to you shortly.

    Regards,

  • 0 in reply to Mike O'
    TI__Genius 9140 points

    Hi WILLIE L. MCCAIN,

    thanks for your interest in UC3907.

    UC3907 selects master only if the current on this module is the highest, that means the master module have the highest output votlage.

    if you want to control a module always as master unit, then please make sure this module has a highest output voltage in the system.

    in the datasheet, there is no any description for the number that can be in parallel. And the control logic is the same with UCC29002, so you can refer to 

    datasheet page 2, a 10kohm resistor is placed on the Pin 15. on the page 4, buffer amp SECTION, there is 6mA output source current, and the current share bus max votlage should be equal to VDD of the UC3907. so the number should be 10kohm*6mA/Vmax_voltage.

    if you want to higher the number of the module in parallel, you can just lower the Voltage on the current sense bus. And the easy way is to lower the current senseresistor.

    btw, uc3907 is an old part, TI recommend customer changes to UCC29002, with a smaller pacage and there are a lot document and calculator in the website for you as a reference.

    below is a link to UCC29002.

    www.ti.com/.../UCC29002

  • 0 in reply to David Huang33
    Prodigy 175 points

    OKAY YOU ARE SAYING THAT THE UNIT IS MORE VOLTAGE RELATED THAN CURRENT BECAUSE IF YOU WONT THEM TO SHEAR BUS CURRENT EQUAL YOU CAN ONLY DO THING AND TAHAT IS TO LOWER THE OUTPUT VOLTAGE AND TRY TO MATCH THE OTHERS, BUT THIS IS WHAT THE DEVICE SHOULD DO AUTOMATICALLY IN BUS SHARE IT WILL TRIM UP ARE DOWN BASED ON THE FIRST UNIT SETTING, YOU WILL ALL WAYS HAVE A MASTER IT DEPENDS ON AT WHAT TIME YOU POWER THEM UP BECAUSE IF I HAVE FOUR UNITS IN THE RACK AND I POWER THE THIRD ON UP FIRST IT BECOMES THE MASTER AND 1,2 AND 4 ARE SLAVES ,NOW I  SHOULD BE ABLE TO CYCLE THRU THE UNITS TO DETERMIN WHO I WONT AS SLAVE I GUESS BY GOING THRU EACH ONE AND PUTTING THE UNIT IN STANDBY, UNTIL I GET TO THE UNIT I WONT AS MASTER CORRECT.

    NOW IF YOU ARE TALKING ABOUT ADJ THE OUTPUT VOLTAGE SO THE UNIT DRAWS MORE THAN THE REST WHERE IS THE CURRENT SHARE, IF ALL THE UNITS HAVE THE DEVICE ON BOARD, ALL ARE OFF AND I START WITH THE 1ST UNIT AND THAN THE SEC. AND THE THIRD AND FORTH AT THAT TIME THE MASTER WILL BE THE UNIT WITH THE HIGHEST OUTPUT VOLTAGENOW IF I CYCLE THRU THEM UNTIL I GET TO THE FIRST UNIT THE FIRST UNIT SHOULD MAKE 2,3 AND 4 COMPENSATE TO READ THE SAME SO ONE IS THE MASTER NOW. OKAY LETS SAY NUMBER ONE FAILS SO THE UNIT WITH THE FASTEST RESPONCE WILL BECOME THE MASTER AND THE OTHER TWO SHOULD COMPENSATE TO MATCH THE MASTER, NOW IF I GET A NEW SUPPLY AND INSTALL IT ,AND POWER  IT ON IT WILL NOT  BE THE MASTER BECAUSE THE UNIT THAT WAS THE MASTER WILL FORCE IT TO MATCH THE OTHER TWO BECAUSE IT HAS CONTROL OF THE SHARE BUS, NOW I SHOULD BE ABLE TO TOGGLE THRU THE UNITS UNTIL I GET TO A UNIT THAT I WONT TO BE THE MASTER SIMPLEY BY PUTTING THE OTHERS IN STANDBY AND THIS SHOULD BE ABLE TO BE CONTROLLED BY THE DEVICE WHICH IS THE CURRENT SHARE CONTROLLER, ONCE THE UNITS COME FROM THE TEST DEPARTMENT THE OUTPUT VOLTAGE AND CURRENT LIMIT SHOULD BE SET AND THEY PASSED ALL TEST NOW THEY GO TO THE STOCK ROOM. NOW I CUSTOMER  CALLS TO GET TWO UNITS TO RUN IN PARRELL HE GET THE UNITS IN AHE PUT ONE OVER HERE AND ONE OVER THERE CLOSE TO HIM AND HE WONTS THAT UNIT TO BE THE MASTER HOW WILL HE SELECT THE MASTER, BY CARING A SCREW DRIVER NO EACH UNIT SHOULD HAVE A PUSH BUTTON FOR THAT FUNCTION AND SIMPLY PRESS THE UNIT BUTTON IT FORCES THE OTHER TO BE THE MASTER BECAUSE BOTH UNIT ARE ADJUSTED FOR THE SAME THING FROM STOCK YOU DONT WONT THE CUSTOMER PLAYING WITH ANYTHING  THATS THE PURPOSE OF CURRENT SHARE TO HAVE A MASTER AND SLAVE 2 UNITS ARE 9 UNITS TOGGLE THRU TO SELECT THE ONE  YOU NEED AS MASTER.

    LET ME NO 

  • 0 in reply to willie mccain
    TI__Genius 9140 points

    Hi willie,

    can you help me to fully understand you question? I can not get your point.

    btw, I suggest you can distinguish between uppercase and lowercase letters

    wenbin

  • 0 in reply to David Huang33
    TI__Genius 9140 points

    Hi willie,

    I still do not receive the feedback from you.

    Please keep in mind the highest output voltage module is the master one.

     other module increase the output votlage to achieve the current sharing.