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TLC5970 - Programming EEPROM

Ilgaz Az
Prodigy 70 points

Dear TI;

One of our project, we plan to use TLC5970. We are building video display unit and total pixel will be 50K.

After reading datasheet, we are really surprised about EEPROM programming procedure. In this case, manufacturing of huge number of products will be hard to handle.

For EEPROM power supply - VROM - must be applied to all units to program EEPROM. Then, it should be released from PCB. 

As you know, soldering VROM pin for programming and desoldering would be time-consuming for 50K module production.

OR, is there any way to configure TLC5970 accordingly when it is shipped?

What is the best and offered way of programming EEPROM? Need your guidance for manufacturing huge amount of production. For correct operation, every TLC5970's EEPROM 1 and EEPROM 2 should be programmed, as I knew.

  • 0
    TI__Intellectual 1820 points

    Hello Az,

    Thank you for choosing TLC5970

    Yes, solder VROM pin is time-consuming in production. How about add a jumper between VIN and VROM on your board as below picture? You can just apply 19V as Vin, and keep jumper in short state when program EEPROM. After that, just let jumper in open state.

    thank you

    Mike

  • 0
    Guru 22270 points

    Hello,

    If you are doing that many, you may want to consider building/buying a gang programmer If that is possible with the i2c EEPROMs. That way you would only have to put a pad on the board since you would not want anyone to just reprogram it.  

    Perhaps TI can do a preprogrammed version for you.

  • 0 in reply to Mike(DC/DC) Wang
    Prodigy 30 points

    Dear Mike,

    Mr. Ilgaz is my teammate.

    After some discussing an idea came to our mind.

    In our design we will use 36V for VCC.

    What if we design a basic transistor circuit like this; 

    With this circuit we can apply 19V to VROM pin when our VCC is 19V. If VCC is 36V, VROM will be 0V. 

    At this point we want to ask you some issues. 

    1. VROM should be delayed in application notes (SBVA036 fig. 2) According to SBVA036 VROM should be applied 10ms after VCC. Is this must? 

    2. If this circuit works properly then can we program multiple eeprom at a time with cascading connection? 

    Regards.

  • 0 in reply to Ali Yuce
    TI__Intellectual 1820 points

    Hello, Ali,

    So, you would rather adding some circuit than just adding a cheap 2pin jumper? The purpose is to save time(short jumper, and take off the jumper cap) in production, right?
    If this is the case, Your proposed circuit will have a problem: Due to the current consumed by VROM is 5mA(typical), the voltage drop accross R3 will be 50V!
    Could you change to below circuit?

    When VCC>32V, Q1 is on, Q2 is off, no VROM voltage;  You can use 36V for normal working condition.

    When VCC<30V, Q1 is off, Q2 is on, VROM=~19V. You can use, say, 24V , when you want to program EEPROM.

    Thank you

    Mike

  • 0 in reply to Mike(DC/DC) Wang
    TI__Intellectual 1820 points

    Sorry, forget reply your other questions.

    for Question1, will check with designer, then come back to you.

    For question2, Yes, you can program all chips in one time as long as they are properly cascaded.

    Best regards

    Mike

  • 0 in reply to Mike(DC/DC) Wang
    TI__Intellectual 1820 points

    Hello,

    I checked with designer, it's no problem because main circuit is reset during VCC power up

    The reason we suggest that timing requirement is for one condition concern: In case VROM reach 19V, then VCC begin rise up, before VCC reach ~4.1, the internal main circuit state is not defined. We do not want EEPROM be mis-programmed accidently.

    In your case, when power up, VCC and VROM start up at same time. Before VROM reach 19V, IC already finished power up reset.

    Best regards

    Mike