Change the PL supply voltage on Ultra96V2

Question

Hi everybody! I want to change the voltage of the power supply of my PL (Vcc_int) in order to carry out tests on the XCZU3EG FPGA. Here is what I understood: Access to PMIC through the I2C MUX (see sheet 25 " AES-ULTRA96-G" attachment and " tca9548a" which is the i2C MUX DataSheet) I2C MUX adress : 0x75 Channel to communicate with PMIC : 0x10 Write in the BUCK2 register in the PMIC to change Vcc_int (see sheet 26 "AES-ULTRA96-G" and " tiduep5a " which is the PMIC DataSheet) PMIC adress : 0x5E (see table sheet 42 "tps650861") BUCK2 register adress : 0x21 (see table sheet 23 "tps650861") Value to change tension (see table sheet 23 " tps650861") This is what i did : Vivado : Vitis : C code : My question is : Is it possible to modify the BUCK 2 register by sending the information to the chain with the XIicPs_MasterSendPolled function ? The I2C MUX is the master and PMIC the Slave. Thanks for the help Justin 
 Attachments: AES-ULTRA96-G_2018-03-19.pdf AES-ULTRA96-G_2018-03-19.pdf tca9548a.pdf tps650861.pdf tiduep5a.pdf

ctammann · Answer

Hey Justin,

we have never tried to manipulate the PMICs individually through the PMBus in the way you are describing. That's not to say it couldn't work, but you are heading into uncharted waters. I'd be leery of making any changes in this way because it hasn't been validated and a mistake could brick your board. Another thing to consider is that we have the INT, INT_IO and BRAM all tied to the same output. Changing that voltage will change all 3 and that may not be what you want. Making changes in that way will void your warranty as we also recommend not making changes to the PMIC configurations. The functionality is there mainly for monitoring purposes and to fix known issues if they come up.

Sorry I don't have a better answer for you, but I'd be very nervous about trying to change that supply that way.

Change the PL supply voltage on Ultra96V2

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