Method and apparatus for use in digitally tuning a capacitor in an integrated circuit device
A method and apparatus for use in a digitally tuning a capacitor in an integrated circuit device is described. A Digitally Tuned Capacitor DTC is described which facilitates digitally controlling capacitance applied between a first and second terminal. In some embodiments, the first terminal comprises an RF+ terminal and the second terminal comprises an RF− terminal. In accordance with some embodiments, the DTCs comprise a plurality of sub-circuits ordered in significance from least significant bit (LSB) to most significant bit (MSB) sub-circuits, wherein the plurality of significant bit sub-circuits are coupled together in parallel, and wherein each sub-circuit has a first node coupled to the first RF terminal, and a second node coupled to the second RF terminal. The DTCs further include an input means for receiving a digital control word, wherein the digital control word comprises bits that are similarly ordered in significance from an LSB to an MSB.
1. A tunable matching network (TMN) comprising a digitally tunable capacitor, the digitally tunable capacitor comprising
a series arrangement of one or more capacitive elements and two or more stacked switches;
a respective drain-source resistor coupled across a drain and source terminal of each the two or more stacked switches, and
a respective gate resistor coupled to a gate terminal of each the two or more stacked switches;
wherein
the two or more stacked switches are configured to withstand a voltage greater than a voltage withstood by one switch;
each of the two or more stacked switches has a control node connectable to a control signal via the respective gate resistor;
the control signal is configured to enable or disable the two or more stacked switches, thereby adjusting the capacitance between the first node and the second node;
the one or more capacitive elements have capacitance values assigned according to a capacitance weighting scheme and the two or more stacked switches have switch sizes assigned according to a switch size weighting scheme, the switch size weighting scheme being a function of the capacitance weighting scheme;
each respective drain-source resistor has a same resistance value assigned according to a drain-source resistor weighting scheme that is inversely proportional to the capacitance weighting scheme, and
each respective gate resistor has a same resistance value assigned according to a gate resistor weighting scheme that is inversely proportional to the capacitance weighting scheme.
2. The TMN of claim 1 , being a tunable antenna matching network.
3. A circuital arrangement comprising an amplifier and the TMN of claim 1 .
4. The circuital arrangement of claim 3 , wherein the amplifier is a power amplifier.
5. An integrated circuit (IC) comprising the circuital arrangement of claim 3 .
6. An integrated circuit (IC) comprising the circuital arrangement of claim 4 .
7. An RF tunable filter comprising a digitally tunable capacitor, the digitally tunable capacitor comprising
a series arrangement of one or more capacitive elements and two or more stacked switches;
a respective drain-source resistor coupled across a drain and source terminal of each the two or more stacked switches; and
a respective gate resistor coupled to a gate terminal of each the two or more stacked switches;
wherein
the two or more stacked switches are configured to withstand a voltage greater than a voltage withstood by one switch;
each of the two or more stacked switches has a control node connectable to a control signal via the respective gate resistor;
the control signal is configured to enable or disable the two or more stacked switches, thereby adjusting the capacitance between the first node and the second node;
the one or more capacitive elements have capacitance values assigned according to a capacitance weighting scheme and the two or more stacked switches have switch sizes assigned according to a switch size weighting scheme, the switch size weighting scheme being a function of the capacitance weighting scheme;
each respective drain-source resistor has a same resistance value assigned according to a drain-source resistor weighting scheme that is inversely proportional to the capacitance weighting scheme, and
each respective gate resistor has a same resistance value assigned according to a gate resistor weighting scheme that is inversely proportional to the capacitance weighting scheme.
8. The TMN of claim 1 , wherein the two or more stacked switches are stacked SOI MOSFET switches.
9. The TMN of claim 1 , wherein the two or more stacked switches comprise three or more stacked switches.