Phase-locked loop having temperature-compensated bandwidth control

A phase-locked loop integrated on a single semi-conductor chip and comprising:

• a phase/frequency detector that compares a reference clock with an output clock and generates an appropriate charge pump control voltage;
• a charge pump coupled to the phase/frequency detector that generates a loop filter control current from the charge pump control voltage;
• a loop filter coupled to the charge pump that generates a loop filter voltage from the loop filter control current, the loop filter comprising a first well resistor and a first capacitor connected in series, and a second capacitor connected in parallel with the first well resistor and first capacitor;
• an oscillator coupled to the loop filter comprising a voltage-to-current converter that generates a reference current based on the loop filter voltage, and a current-controlled oscillator that generates the output clock based on the value of the reference current;
• wherein the voltage-to-current converter comprises a first transistor that receives the loop filter voltage at a gate and a second well resistor coupled to the source of the first transistor, the second well resistor and first well resistor having substantially equal resistances and temperature coefficients;
• and
• a feedback circuit coupled between the oscillator and the phase/frequency detector that provides the output clock signal to the phase/frequency detector.

A method for counteracting bandwidth perturbations due to temperature fluctuations comprising the following steps:

• (a) providing a phase-locked loop having a first temperature-sensitive element;
• (b) obtaining a second temperature-sensitive element;
• and
• (c) situating the second temperature-sensitive element in the phase-locked loop to counteract perturbations in the loop bandwidth due to temperature fluctuations.

A method for providing a substantially constant bandwidth in a phase-locked loop having a loop filter and an oscillator, the method comprising the following steps:

• (a) obtaining a first temperature-variable resistor R1;
• (b) situating resistor R1 in the phase-locked loop such that the gain of the loop filter is directly related to R1;
• (c) obtaining a second temperature-variable resistor R2;
• and
• (d) situating resistor R2 in the phase-locked loop such that the gain of the oscillator is inversely related to R2, wherein the bandwidth is a product of the loop filter gain and the oscillator gain.