Crystal-less oscillator circuit with trimmable analog current control for increased stability

A phase locked loop circuit comprising:

• a phase detector circuit;
• and
• a voltage controlled oscillator circuit comprising:
• a digital to analog converter circuit for generating a current and comprising a voltage to current converter circuit for converting a control voltage to a first current and a trimmable current control for generating a second current, wherein said current is a sum of said first current and said second current;
• a band gap reference circuit for generating a voltage based on process variations;
• and
• a relaxation oscillator circuit coupled to said digital to analog converter circuit and said band gap reference circuit and for generating a frequency based on said current and said voltage.

A microcontroller comprising:

• a bus;
• a processor coupled to said bus;
• a memory unit coupled to said bus;
• a phase locked loop circuit for generating a frequency and coupled to said bus and comprising:
• a phase detector circuit;
• and
• a voltage controlled oscillator circuit comprising:
• a digital to analog converter circuit for generating a current and comprising a voltage to current converter circuit for converting a control voltage to a first current and a trimmable current control for generating a second current, wherein said current is a sum of said first current and said second current;
• a band gap reference circuit for generating a voltage based on process variations;
• and
• a relaxation oscillator circuit coupled to said digital to analog converter circuit and said band gap reference circuit for generating a frequency based on said current and said voltage.