Radio frequency switch control circuitry
Apparatus and methods for radio frequency (RF) switch control are provided. In certain embodiments, a level shifter for an RF switch includes a first level-shifting n-type transistor, a first cascode n-type transistor in series with the first level-shifting n-type transistor between a negative charge pump voltage and a first output that provides a first switch control signal, a first level-shifting p-type transistor, a first cascode p-type transistor in series with the first level-shifting p-type transistor between a positive charge pump voltage and the first output, and a second cascode p-type transistor between a regulated voltage and a gate of the first level-shifting n-type transistor and controlled by a first switch enable signal.
1. A mobile device comprising:
a power management system including a positive charge pump configured to generate a positive charge pump voltage, a negative charge pump configured to generate a negative charge pump voltage, and a voltage regulator configured to generate a regulated voltage; and
a front end system including a radio frequency switch controlled by a first switch control signal, and a level shifter operable to level shift a first switch enable signal to generate the first switch control signal at a first output, the level shifter including a first enable level shifter powered by the positive charge pump voltage and configured to receive the first switch enable signal and to output a first level-shifted switch enable signal, a first level-shifting n-type transistor and a first cascode n-type transistor in series between the negative charge pump voltage and the first output, and a first level-shifting p-type transistor and a first cascode p-type transistor in series between the positive charge pump voltage and the first output, the first level-shifting p-type transistor having a gate controlled by the first level-shifted switch enable signal, and the first cascode n-type transistor having a gate connected to the regulated voltage.
2. The mobile device of claim 1 wherein the level shifter further includes a second cascode p-type transistor between the regulated voltage and a gate of the first level-shifting n-type transistor.
3. The mobile device of claim 2 wherein the level shifter further includes a third cascode p-type transistor and a second level shifting n-type transistor in series with the third cascode p-type transistor between the regulated voltage and the negative charge pump voltage.
4. The mobile device of claim 2 wherein the level shifter further includes a second level shifting n-type transistor in series with the second cascode p-type transistor between the regulated voltage and the negative charge pump voltage.
5. The mobile device of claim 2 wherein a gate of the second cascode p-type transistor is controlled by a second switch enable signal.
6. The mobile device of claim 5 wherein the level shifter further includes a second enable level shifter configured to receive the second switch enable signal and to output a second level-shifted switch enable signal, the second enable level shifter powered by the positive charge pump voltage.
7. The mobile device of claim 1 wherein the front end system further includes a power amplifier configured to provide a radio frequency signal to the radio frequency switch.
8. A level shifter for a radio frequency switch, the level shifter comprising:
a first enable level shifter configured to receive a first switch enable signal and to output a first level-shifted switch enable signal, the first enable level shifter powered by a positive charge pump voltage;
a first level-shifting n-type transistor;
a first cascode n-type transistor in series with the first level-shifting n-type transistor between a negative charge pump voltage and a first output that provides a first switch control signal, a gate of the first cascode n-type transistor connected to a regulated voltage;
a first level-shifting p-type transistor having a gate controlled by the first level-shifted switch enable signal; and
a first cascode p-type transistor in series with the first level-shifting p-type transistor between the positive charge pump voltage and the first output.
9. The level shifter of claim 8 further comprising a second cascode p-type transistor between the regulated voltage and a gate of the first level-shifting n-type transistor.
10. The level shifter of claim 9 further comprising a third cascode p-type transistor and a third level shifting n-type transistor in series with the third cascode p-type transistor between the regulated voltage and the negative charge pump voltage.
11. The level shifter of claim 9 further comprising a second level shifting n-type transistor in series with the second cascode p-type transistor between the regulated voltage and the negative charge pump voltage.
12. The level shifter of claim 9 wherein a gate of the second cascode p-type transistor is controlled by a second switch enable signal.
13. The level shifter of claim 12 further comprising a second enable level shifter configured to receive the second switch enable signal and to output a second level-shifted switch enable signal, the second enable level shifter powered by the positive charge pump voltage.
14. A radio frequency switch system comprising:
a radio frequency switch configured to receive a radio frequency signal and controlled by a first switch control signal;
a positive charge pump configured to generate a positive charge pump voltage;
a negative charge pump configured to generate a negative charge pump voltage;
a level shifter operable to level shift a first switch enable signal to generate the first switch control signal at a first output, the level shifter including a first enable level shifter powered by the positive charge pump voltage and configured to receive a first switch enable signal and to output a first level-shifted switch enable signal, a first level-shifting n-type transistor and a first cascode n-type transistor in series between the negative charge pump voltage and the first output, and a first level-shifting p-type transistor and a first cascode p-type transistor in series between the positive charge pump voltage and the first output, the first level-shifting p-type transistor having a gate controlled by the first level-shifted switch enable signal; and
a voltage regulator configured to generate a regulated voltage, a gate of the first cascode n-type transistor connected to the regulated voltage.
15. The radio frequency switch system of claim 14 wherein the level shifter further includes a second cascode p-type transistor between the regulated voltage and a gate of the first level-shifting n-type transistor.
16. The radio frequency switch system of claim 15 wherein the level shifter further includes a third cascode p-type transistor and a second level shifting n-type transistor in series with the third cascode p-type transistor between the regulated voltage and the negative charge pump voltage.
17. The radio frequency switch system of claim 15 wherein the level shifter further includes a second level shifting n-type transistor in series with the second cascode p-type transistor between the regulated voltage and the negative charge pump voltage.
18. The radio frequency switch system of claim 15 wherein a gate of the second cascode p-type transistor is controlled by a second switch enable signal.