Two Masters on Same SMBus

I want to use EVKT-USBI2C-02 in order to write to MPS (MP2940A) Multi-phase Controller using PMBUs (a variant of SMBus, based on I2C).

I have two controllers on my motherboard, one for is for controlling VCCIN (3 phases) and the second for VCCIN_AUX (1 phase). both voltages are supply voltages for Intel Tiger Lake UP3 CPU.

I have an edge connector on my motherboard with an adapter card that connects between EVKT-USBI2C-02 and the MP2940A devices on motherboard through ribbon cable.

Note: EVKT-USBI2C-02 is also connected through USB To external PC on which we will put the EVKT-USBI2C-02 software.

as far as I understood from MPS, EVKT-USBI2C-02 has C8051F320 MCU.

First, It’s not clear whether I need to add pull-up resistors for the SCL, SDA signals on my motherboard or EVKT-USBI2C-02 already has the Pull-up resistors inside, I will need to ask MPS again, but I would be happy if someone can already answer this question and tell how can one know that with only with this information provided (I didn’t find schematic for EVKT-USBI2C-02).

Second, I have an main SMBus on my motherboard where the CPU is the master for it. I’m not sure whether I need to create separate SMBUS for that relevant to C8051F320 (as master) and MP2940A (as slave) or just connect two masters (C8051F320 and Intel CPU) on same bus. on this option I understand that there is no need for extra pull up resistors, because the main bus already has ones. what are the considerations needed for the second option?

Third, why EVKT-USBI2C-02 does not have an ALERT signal? isn’t it necessary for the two masters case?

Note: the two MP2940A have different slave addresses.

Hi firas.abdelghani

Thank you for contacting the MPS Forum. I’m looking at your question and will work on getting you an answer soon.

Brendan Schoemehl
Field Applications Engineer
Monolithic Power Systems | MPS Now