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SPI Communication Failure with LTC6803 and LTC3300

Category: Software
Product Number: LTC6803-3


I'm using a stm32l452ret to communicate directly with the LTC6803 and LTC3300 without an SPI Isolator. Unfortunately, I have yet to have a response from either chip when sending them simple commands like reading config registers on startup for the ltc6803-3 and reading the balance state for the ltc3300. All i'm trying to do is detect of the chips are able to respond before attempting further communication. Is an isolator between the microcontroller and ics necessary? Is it meant to be fine as long as I have both grounds tied together? 

Thanks for your help in advance.

  • Hello,

    The isolator is only to protect the PC in case the unlikely event that something happens on the eval board that can violate the voltage on the signals or power from the PC. The Isolator can removed and the signals and power to the board can be connected by shorting the resistors to connect power, gnd, and the signals. 

  • Thank you. That make sense and is what I presumed.

    What would be a likely cause to not receive any reply from the ICs in that case? The V- of the chip is connected to the GND of the MCU so I don't that should be the issue. The MCU works on a logic high of 3.3 which should be more than enough for the logic high specified in the data sheet of the LTC6803. However, I can't short Vreg to Vdd of the MCU as they are different voltage levels so only GND can be connected together.