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Cascade Connection

Category: Hardware
Product Number: LTC6811-1

Hello to ADI support team ,

      I have some questions  according LTC6811-1 , 2 units connection on the same board for 20S configuration .

1. Coupling Configuration from Data sheet there is 2 options : A - CMC + Capacitors , B - CMC + Signal Transformer .

       1.1.  If my IC's (LTC6811-1)  on the same board is it sufficient make signal coupling through the simplest form through Capacitors ?

2.  Can I use  SPI Communication through the bottom IC directly without LTC6820 ?

3.  Can I use I2C directly to the  Controller from the bottom LTC6811-1 ?

4.   What is the main reason data sheet introduce Controller Connection with LTC6811-1 through LTC6820 ?

5.   Do you have dedicated guide for cascade connection for high capacity packs ?

B.R

Alexander Burtakov

Top Replies

  • Answers to your questions -

    1. For same board isoSPI communication you can use capacitors. (only for 6811 to 6811. for 6820 to 6811 you will need to use transformer) 

    2. We will recommend you to use LTC6820 as you have 20S configuration. Isolation to controller is needed. 

    3. What is the intention for using I2C? We only recommend using I2C to control smaller devices like EEPROM or digital temp sensor. Communication to controller is not recommended as it will break the isolation. 

    4. HV isolation

    5. Recommended application diagram in datasheet is our latest reference and can be used for making the daisy chain connection. 

  • Hello Abhishek ,  thank for answers ,

       1. I want to point MPU communication with 6811-1 , There is a stock problem with IC you recommend LTC6820 .   Is  Option A and B are acceptable ?

         A : Use SPI pins in 6811-1 direct to SPI isolated IC ( not 6820) ?

         B:  Use I2C pins in 6211-1 direct to isolated I2C device ? 

      2.    It is 8 Part number names of 6811-1 , 4 are High Temp , 4 are Industrial , half are automotive and half regular .   If Temperature rating is not issue for me , Can I use with all 8 Part numbers ?  Is it another difference between them?

    B.R

    Alexander Burtakov

  • A : Use SPI pins in 6811-1 direct to SPI isolated IC ( not 6820) ?

    Yes. This is possible. You can use the SPI port available in Pins 41 to 44 to communicate with the IC. For more info, please refer "4-WIRE SERIAL PERIPHERAL INTERFACE (SPI)" subsection under the Serial Interface Overview section in LTC6811 Datasheet Rev.C (Page no. 44).

    B:  Use I2C pins in 6211-1 direct to isolated I2C device ? 

    No. The I2C lines available on GPIO pins 4 and 5 are I2C Initiator pins, which can be used to communicate with secondary devices (like EEPROMs, Digital Temperature Sensors, etc.) using the COMM commands. For more, info please refer " I2C/SPI MASTER ON LTC6811 USING GPIOS " section in LTC6811 Datasheet Rev.C (Page no. 39).


    Is it another difference between them?

    No. Functionally there are no differences between them except for the specified temperature range.

  • Hi SideshS , thanks for your reply .

       I want to clear some points to verify i forward proper  aplimintation.

          1. Yes. This is possible. You can use the SPI port available in Pins 41 to 44 to communicate with the IC. For more info, please refer "4-WIRE SERIAL PERIPHERAL INTERFACE (SPI)" subsection under the Serial Interface Overview section in LTC6811 Datasheet Rev.C (Page no. 44).   -->  I intend use ADUM7441 ( Quad general USE digital isolator) between 6811-1 and my MPU , is it suitable in your opinion ?

          2. No. The I2C lines available on GPIO pins 4 and 5 are I2C Initiator pins, which can be used to communicate with secondary devices (like EEPROMs, Digital Temperature Sensors, etc.) using the COMM commands. For more, info please refer " I2C/SPI MASTER ON LTC6811 USING GPIOS " section in LTC6811 Datasheet Rev.C (Page no. 39).   --> I don't clear understand the reason why connection 6811-1 through GPIO 4/5 SDA/SCL  to I2C isolator Primary side , and from I2C isolator secondary side to MPU will not work in the same manner like in SPI par .1 

    B.R

    Alexander Burtakov

  • I intend use ADUM7441 ( Quad general USE digital isolator) between 6811-1 and my MPU , is it suitable in your opinion ?

    Yes. This is possible and LTC6811 will function as expected even in this configuration.


    I don't clear understand the reason why connection 6811-1 through GPIO 4/5 SDA/SCL  to I2C isolator Primary side , and from I2C isolator secondary side to MPU will not work in the same manner like in SPI par .1 

    You can have an isolator in-between the GPIO lines and other devices. One important thing to note here is these I2C Lines in GPIO 4/5 are Master I2C lines and you can use them to communicate with any other I2C device with the help of LTC6811's COMM commands but you cannot send commands to LTC6811 through these Master I2C lines. 
    Maybe, I misunderstood your question in your second last reply thinking you are asking about controlling the LTC6811 through those I2C lines since this thread was started regarding the cascade connection of devices. 

  • Hello to Analog support team ,
    I use 2 serias connected LTC6811-1 to monitor 20S connection ( 10 cell / each IC ) with regular SPI communication with bottom IC.

    Some question for claification:
    1. S6,S12 is not in use , leave this pins NC ?
    2. Upper IC IPB/IMB pins connect to each other through 100 ohm ?
    3. DTEN , WDT --> It seems that i need monitor 4 signals with microcontroller to bottom LTC6811-1 and to upper LTC6811-1 ?
    4. 20S configuration , 10 each IC :
    4.1 C5&C6 shorted , C11&C12 shorted ?
    4.2 10P connected --> 1. with bottom IC C11,C12 through RC filter and to upeer IC to C0 ?

    B.R

    Alexander Burtakov

  • 1. S6,S12 is not in use , leave this pins NC ?

    Yes, you can leave these pins NC or connect them to the battery stack similar to C pins.

    2. Upper IC IPB/IMB pins connect to each other through 100 ohm ?

    Yes, you should terminate the unused isoSPI ports with 100 Ohms.

    3. DTEN , WDT --> It seems that i need monitor 4 signals with microcontroller to bottom LTC6811-1 and to upper LTC6811-1 ?

    If you want to control the device from transitioning between the sleep or extended balancing state on the watchdog timer timeout, then you need a digital output pin from the controller to connect to DTEN pin. Similarly, if you want to know if the device's watchdog timer expired, then you need a digital input pin in your controller for the same.

    4.1 C5&C6 shorted , C11&C12 shorted ?

    Yes. You can find more info in the "Using the LTC6811 With Fewer Than 12 Cells" section under applications information in the datasheet(Page No. 86).

    4.2 10P connected --> 1. with bottom IC C11,C12 through RC filter and to upeer IC to C0 ?

    Yes, Also add a filter resistor before C0.