Power (AxelLite)
Revision as of 08:10, 15 July 2014 by DevWikiAdmin (talk | contribs) (→Power rails and related signals)
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Power Supply Unit (PSU) and recommended power-up sequence[edit | edit source]
Implementing correct power-up sequence for i.MX6 processors is not a trivial task because several power rails are involved. Axel Lite SOM simplifies this task by embedding all the needed circuitry. The following picture shows a simplified block diagram of PSU/voltage monitoring circuitry:
The PSU is composed of two main blocks:
- power management integrated circuit (PMIC, Freescale PF0100E0 - on request this part is available in automotive grade)
- additional generic power management circuitry that completes PMIC functionalities.
The PSU:
- generates the proper power-up sequence required by i.MX processor and surrounding memories and peripherals
- synchronizes the powering up of carrier board in order to prevent back power
- provides some spare regulated voltages that can be used to power carrier board devices
Power-up sequence[edit | edit source]
The typical power-up sequence is the following:
- (optional) PMIC_LICELL is powered
- 3.3VIN main power supply rail is powered
- CPU_PORn (active-low) is driven low
- PMIC activates PMIC_VSNVS power output
- PMIC_PWRON signal is pulled-up (unless carrier board circuitry keeps this signal low for any reason)
- PMIC transitions from OFF to ON state
- PMIC initiates power-up sequence needed by MX6 processor
- BOARD_PGOOD signal is raised; this active-high signal indicates that carrier board circuitry interfacing Axel Lite I/O has to be powered up
- CPU_PORn is released.
[edit | edit source]
The following list describes in detail the power rails and the power related signals. Please note that PMIC regulators ouput voltages can be changed only if explicitly allowed.
- 3.3VIN: this is external main power rail. Voltage range is 3.3V±5%
- PMIC_CELL: PMIC's coin cell supply input/output
- BOARD_PGOOD: this output signal is used to indicate when carrier board's circuitry interfacing Axel Lite's I/Os has to be powered up.
For further details, please refer to the PMIC documentation.
