Kindly ask to get confirmation on my understanding of the power-up sequence.
- Main power source is connected – using DC Jack VCC_DCIN is powered from the AC/DC adapter, and the voltages goes (through FETs) to VCC_SRC_FET. VDD_3V3_PD is also created from VCC_DCIN. VCC_SRC_FET is used to create 5V_AO, and 3V3_AO is generated from 5V_AO.
- The carrier releases VDDIN_PWR_BAD_N which will be used later by the module.
- When the user press the power-button, the carrier VIN_PWR_ON signal is created, and switches on the supplies for SYS_VIN_HV (VCC_SRC) and SYS_VIN_MV (VDD_5V), then the carrier releases ‘MODULE POWER_ON’.
- When the module internal supplies are stable, and the VDDIN_PWR_BAD_N is high, the module asserts ‘CARRIER_POWER_ON’, which directly enables the VDD_1V8 and VDD_3V3 supplies, and is input to the SRC0GS22D. (The module also de-asserts SYS_RESET_n, but it is still asserted low by the carrier)
- When all supplies are OK, the carrier releases the SYS_RESET_N, and PERIPERAL_RESET_N, and the SOM starts running
Kindly asks for explanation on the usage of POWER_BTN_N input to the SOM - what are the purposes and usage.
(I assume that this is for long-power-button-off event)