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LTPowerPlay I2C Base Addressing

My question is regarding the DC1962C demo board. I'm using LT power play to communicate with it via the DC1613A programming pod. 

I looked at the schematic and saw for the LTC2974, the ASEL1 pin is tied LOW and ASEL0 is tied HIGH. The Address look-up table (Table 1) on the LTC2974 datasheet says this would correlate to a 7-bit hex base address of 0x5E. But LTpowerplay tells me that the LTC2974 on the demo board detects a 7-bit hex base address of 0x32. I was wondering if there was something I’m overlooking? Trying to understand why the software wouldn’t show 0x5E. An Post y help is appreciated!

  • Hi ZD;

    The advice I received is:

    The ASEL pins just add to the base address.  Sometimes we call it an offset, in this case offset=2.  The 2974’s address will be 0x5E only if the base address is 0x5C (default).  The I2C base address is a PMbus register that is programmed (stored in chip’s NVM), and in the case of the DC1962 we reprogrammed it to 0x30.  We moved the base address to give more room when you stack demo boards together. You can plug many boards together and LTpp will enumerate all devices in the system tree starting at 0x30.  You can't assign addresses above 0x7F.