Patent ID: 7535309

Claim:
A tunable clock generator comprising: a VCO having a control input and a power node; a first IPTAT current generator; a variable resistor bank receiving current from the first IPTAT current generator; wherein the IPTAT current generator and the variable resistor bank provide the control input to the VCO; and wherein the variable resistor bank comprises a set of resistors arranged in selectable combinations of resulting resistances and resulting temperature coefficients, and wherein the selected resulting resistance trims the output frequency of the VCO and the temperature coefficient profile of the clock generator is selectably non-linear over an operating temperature, and wherein the set of resistors are connected in series and in parallel, and a set of switches are connected in series with the resistors, wherein the switches are activated by a set of digital inputs that turn on or off the switches, wherein combinations of different series and parallel resistors are selected, and wherein the resistors have different resistance values and different temperature coefficients, wherein the value of an equivalent resistance for a selected set of series and parallel resistances, and the resulting temperature coefficients for the equivalent resistance is selected to provide a control voltage to the VCO to provide a selected clock frequency with a selected temperature coefficient.