There are three power lines on IMX178, they are called:
- Analog 2.9V Supply (AVDD)
- Digital 1.2V Supply (DVDD)
- Interface 1.8V Supply (OVDD)
Foturnately, there are existing power regulator chips on the sensor board to generate the 3 supplies from the main 3.3V supply from the Microcontroller board, as illustrated below:
Accroding to the documentation page 96~97, there is a specific Power-on/off Sequence to be followed. (DVDD first, OVDD second, AVDD last, followed by XCLR cancellation and then INCK)
There are futrher instructions to be followed, such as things related to I2C.
The power-on timing is already taken cared of by the RC circuits built into the Sensor Board. However, the power-off timing may or may not be taken care of from observation. nevettheless, it may not matter for normal operations.
NOTE: The mysterious DVDD_SENSOR line seems redundant. I cannot confirm the use of it. But according to “Hi3516AREFB VER.D” reference design, it is used to channel back the 1.8V to DVDD3318_SENSOR pin at Hi3516 chip, hence not relevant to our design.
We can confirm this by multi-metering the pin see if it has a hot 1.8V running through.