STK1000/Power system
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General
STK1000 have a complex power system generating several voltages. The voltage supplies are sequenced such that the highest voltages activate first.
Block diagram
The power system of STK1000 consist of three switched regulators and one linear regulator. A 2.1mm DC jack cable or the dual screw terminal can be used to connect power to the system. A power switch is included to turn on and off power on the board. A high current diode ensures that correct polarity is applied and a PolySwitch limits the total current to the starter kit.
Signals
The four regulators have the following features.
- The 5.0V switched regulator is the master regulator delivering power to all other power regulators. The reason for this is the allowed input voltage range for the remaining regulators.
- The 3.3V switched regulator deliver power to all peripherals on the board. STK1000 is a 3.3V system.
- The 2.5V linear regulator deliver power to the core of the Ethernet physical interface only
- The 1.8V switched regulator deliver power to the AVR32 CPU core only.
Power sequencing
Power is sequenced implemented such that the 3.3V enable the 2.5V regulator and the 2.5V regulator enable the 1.8V regulator. The power LED on STK1000 is turned on by the 1.8V regulator. The 3.3V regulator will not turn on the 2.5V regulator unless the output value is within 5% of nominal value. The 2.5V regulator will not turn on the 1.8V regulator unless the 2.5V level falls below 10% of nominal value. Finally the power LED will not turn on unless the 1.8V output voltage is within 5% of nominal value.
If the power LED is not turned on, then you should measure the voltage levels of the 6 pin power header to ensure that all the voltages are correct.
Current capabilities of the power converters.
The power supplies are limited by the internals of the converter and the inductors used for the switched power supplies. Since the 5.0V converter deliver power to the other converters the maximum current for this converter is a function of the other converters. The same applies for the 3.3V converter.
The maximum current that can be drawn from the different voltage converters are given listed below. The listed current is the current that board peripherals and user expansion boards can draw together. Note that the 1.8V supply is only designed for use by the daughter board CPU.
Voltage | Recommended maximum current |
---|---|
5.0V | 0.5 A |
3.3V | 1.4 A |
2.5V | 800 mA |
1.8V | 800 mA |
6 pin power header
All system voltages are routed to the power header J200. The power header have the following pin out.