Question:
If there is power supply available on the I2CIN pin of MAX8971, but no power supply on the VIN pin, can the on-chip registers be written through the I2C interface?
Answer:
The I2CIN pin provides the power supply voltage for the I2C interface, and the on-chip registers can only be read / written when the VIN voltage is valid.
Therefore, even if the voltage on I2CIN is valid, but the VIN voltage is below UVLO, no data can read/written via the I2C interface.