Important parameters

• Maximum rating
• Power supply - voltage, current consumption
• Reset
• I/O ports parameters
• Flash programming
• Clocking

Maximum ratings

• Microcontrollers have to be viewed as a complicated device, sensitive to many factors
• Each device have their own absolute Maximum Ratings that must be viewed very carefully
• The values found in that table MUST NOT be exceeded

Main parameters:

• Operating temperature
  • usually from -40C to 130C
  • usually different temperature variants available
  • differs from chip vendor to chip vendor
  • Usually NOT protected against overheating
  • Thermal resistance should be taken into consideration in order to avoid problems with overheating

The microcontroller can overheat when:

• we overclock it

• Maximum operating voltage

  • its try to draw to much current (the most common case)
  • For microcontrollers with multiple power supplies inputs, the maximum ...
  • Maximum value of voltage that can be connected

• Input/Output voltage range

  • maximum value of voltage that can be connected to any pin of microcontroller
  • the input-output voltage range can be extended when the CLAMP CURRENT parameter is used properly
  • The value is usually limited by the actual power supply value and may stay within some limits (i.e. -0.5V to VCC +0.5V)

• Clamp current

  • the maximum current that the input can sink or the output can source without any damage
  • usable in ESD protection
  • If a series resistor is used then even very high or negative voltages can be directly connected to the microcontroller
  • Usually in mA range
  • when using big resistor as current limiter we loose the dynamic response, because it makes RC filter

Power supply

1. PS
   • usually it is a delicate task
   • most of uc have more than 1 ps unit
   • each ps input have usually different requirements
   • the most problematic for ps are uc with analog part (mixed signals, sometimes bigger uc require more current like 0.5A, so we have to use special capacitors and thicker traces)
2. Types and choosing
   • We have to choose between linear nad switching (more popular nowadays) ps
   • INPUT ac or dc → OUTPUT unregulated dc → OUTPUT regulated dc
   • Linear only if the clean output is crucial.
   • We should have 50% bigger maximum power than needed
   • Dual supply - different supplies for analog and digital part
   • Single supply - we have additional filtering for analog supplies (BEAD, inductor, capacitor)
   • Decoupling capacitors - VERY important (100nF is standard value), each ps pin has to have decoupling capacitor (Electrolytic capacitors have better transient response than tantalum)
   • Single PS is enoungh up to 12 bits