Hello,
I am testing the MPQ8880AGVE-0000-AEC1 using an Arduino Uno R4 Minima as I²C master.
Current setup:
Device powered and working correctly
Output voltage stable at ~5.0 V
PMBus address: 0x60
Internal feedback divider mode (default configuration)
What works:
Device responds to I²C (ACK OK)
VOUT_COMMAND (0x21) write returns success (no error)
CLEAR_FAULTS (0x03) also works
Problem:
Changing VOUT_COMMAND (for example from 0x341 → 0x226 for ~3.3 V) does not change output voltage
VOUT remains ~5.0 V
I also see unstable behavior when doing multiple transactions (sometimes NACK or bus error)
Additional notes:
I tested single write per reset (to avoid bus issues)
Same result: command accepted, no change on output
I cannot reliably read registers (read operations fail on my setup)
Questions:
Is there any condition required before VOUT_COMMAND takes effect (for example specific mode, register, or sequence)?
Can this MTP configuration (0000) block dynamic VOUT changes via PMBus?
Should VOUT change immediately after writing VOUT_COMMAND in internal feedback mode?
Any guidance would be helpful.
Thank you.