This power supply module meets all the AT91SAM9G20 CPU power requirements and power-up and power-down sequences to guarantee reliable operations. The AT91SAM9G20 CPU used on the Netus G20 module requires a power-up and power-down sequence to guarantee reliable operations. Any deviation from these sequences may lead to excessive current consumption during power-up or prevent the device from booting. Moreover, a 1.8-volt BGA RAM is used to reduce the power consumption enabling low-power modes due to the mobile nature of the SDRAM used, so NetusG20 requires three different voltages -- 1.0, 1.8 and 3.3 volts -- to work. This additional power supply module makes it easier to design a Netus G20 application board. NetusPS1 schematic Netus PS1 pinout: | Pin | line | in/out | Notes | | 1 and 2 | 3V3 | powerout | main 3V3 out for Netus G20 power and peripherals who need to be powered at the same time of the Netus G20. Max current available for peripherals: 500mA | | 3 | 1V0 | powerOut | main 1V0 out for Netus G20. Not for powering other peripherals | | 4 | 1V8 | powerOut | main 1V8 out for Netus G20. Not for powering other peripherals | | 5 | 5V | powerIN | main input voltage 5Volts stabilized (connected also to pin 14) | | 6 | GND | ground | ground (connected also to pins 9 and 15) | | 7 | IN2 | powerIN | input for the spare Low DropOut regulator (normally connected to 5V) | | 8 | PGD | signalOUT | output showing the 5V input is now stable | | 9 | GND | ground | ground (connected also to pins 6 and 15) | | 10 | OUT2 | powerOUT | output for the spare Low DropOut regulator (factory trimmed to 3.25V). Max power deliverable 250mA | | 11 | EN2 | signalIN | enable input active High (+5V) for the spare Low DropOut regulator | | 12 | POK | signalOUT | output signaling that the NetusPS1 outputs 3V3, 1V8 and 1V0 are now permitted to start (see figure 3) | | 13 | SHDN | signalIN | shutdown input (active Low) When lowered to ground NetusPS1 outputs 3V3, 1V8 and 1V0 are switched off. Releasing this pin will restart the correct power up sequence for those three power outputs | | 14 | VCC | powerIN | main input voltage 5Volts stabilized (connected also to pin 5) | | 15 | GND | ground | ground (connected also to pins 6 and 9) | | 16 | 3V3Aux | powerOUT | auxiliary 3V3 power output always present even when SHDN is lowered to ground |
Power-up sequence: 
The image above shows the output voltages of the NetusPS1 power supply powering a NetusG20 board. You can see that when the POK signal (generated by the NetusPS1 itself) raises, the three voltages 1V0, 1V8 and 3V3 start to power up the Netus board. On the image below, there is an enlargement of the power-up sequence where it is possible to see that the 1V0 voltage is the first to start. When 1V0 reaches 0.5 Volts, the other two voltages (1V8 and 3V3) are enabled to start by the logic inside NetusPS1 itself. 3V3 and 1V8 reach 0.7 Volts within 50µs and become steady well within 300µs as per the Atmel AT91SAM9G20 specifications.
Power-down sequence: 
Here above is the power-down sequence for the NetusPs1 powering a NetusG20 board. You can see that 3V3 and 1V8 are switched off at the same time as 1V0 voltage, per Atmel requirements.
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