This info came via the R5 board email discussion group:
Trenz produced and tested first R5 prototypes.
During tests, we discovered a squeaking sound due to the operation of 2 new power supplies MP8869S.
As we found out, this is due to the LLM operating mode, which automatically switches to PWM mode when a certain power consumption threshold is reached.
See description of Reg01 SysCntlreg1 in the datasheet. Unfortunately there is no OTP memory for reconfiguration on production.
Paul asked:
Regarding the power supply noise, am I correct in assuming that we can make the FPGA bitstream control those to select the silent mode of operation?
Answer from Vadim:
That's correct. The FPGA is connected to power supplies via the I2C bus.
MJoergen
commented
6 months ago
This info came via the R5 board email discussion group:
Trenz produced and tested first R5 prototypes.
During tests, we discovered a squeaking sound due to the operation of 2 new power supplies MP8869S. As we found out, this is due to the LLM operating mode, which automatically switches to PWM mode when a certain power consumption threshold is reached. See description of Reg01 SysCntlreg1 in the datasheet. Unfortunately there is no OTP memory for reconfiguration on production.
Paul asked:
Regarding the power supply noise, am I correct in assuming that we can make the FPGA bitstream control those to select the silent mode of operation?
Answer from Vadim:
That's correct. The FPGA is connected to power supplies via the I2C bus.