Apparatus and methods for programmable low dropout regulators for radio frequency electronics

Patent metadata

Field	Value
Publication number	US-9817416-B2
Application number	US-201615219915-A
Country	US
Kind code	B2
Filing date	Jul 26, 2016
Priority date	Aug 17, 2015
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

Apparatus and methods for programmable low dropout (LDO) regulators for radio frequency (RF) electronics are provided herein. In certain configurations, an LDO regulator for generating a programmable output voltage includes a regulation field-effect transistor (FET) having a drain electrically connected to the LDO regulator's output, an error amplifier that controls a gate of the regulation FET, a feedback circuit that provides a feedback signal to an inverting input of the error amplifier, an output capacitor electrically connected to the LDO regulator's output, and an alternative discharge circuit. When the output voltage of the LDO regulator is programmed from a high voltage level to a low voltage level, the alternative discharge circuit activates to discharge the output capacitor to improve the LDO regulator's transient response.

First claim

What is claimed is:

1. A programmable low dropout regulator comprising:
an error amplifier including an output and a first input;
a regulation field-effect transistor including a gate electrically connected to the output of the error amplifier and a drain electrically connected to an output node configured to provide a programmable output voltage that is programmable to a plurality of different voltage levels;
a feedback circuit electrically connected between the output node and a first voltage, the feedback circuit configured to provide a feedback signal to the first input of the error amplifier;
an output capacitor electrically connected to the output node; and
an alternative discharge circuit configured to activate to discharge the output capacitor in response to programming the programmable output voltage from a high voltage level to a low voltage level.

2. The programmable low dropout regulator of claim 1 wherein the alternative discharge circuit includes a comparator configured to compare the programmable output voltage to a trigger voltage, and to selectively activate an electrical path from the output node to the first voltage based on the comparison.

3. The programmable low dropout regulator of claim 2 wherein the alternative discharge circuit further includes a discharge field-effect transistor including a source electrically connected to the first voltage and a gate electrically connected to an output of the comparator.

4. The programmable low dropout regulator of claim 3 wherein the alternative discharge circuit further includes a discharge control circuit electrically connected between the output node and the drain of the regulation field-effect transistor.

5. The programmable low dropout regulator of claim 2 wherein the alternative discharge circuit further includes a trigger voltage generation circuit configured to generate the trigger voltage, the trigger voltage generation circuit including one or more resistors and a current source that provides a current that flows through the one or more resistors to generate the trigger voltage.

6. The programmable low dropout regulator of claim 2 wherein the low dropout regulator is configured to receive a control signal operable to control a programmed voltage level of the programmable output voltage, the alternative discharge circuit configured to adjust a voltage level of the trigger voltage based on the control signal.

7. The programmable low dropout regulator of claim 1 wherein the feedback circuit includes a first resistor and a second resistor electrically connected in series between the output node and the first voltage, the first resistor having a programmable resistance operable to change a programmed voltage level of the programmable output voltage.

8. The programmable low dropout regulator of claim 1 further including a reference voltage generator configured to provide a reference voltage to a second input of the error amplifier.

9. A power amplifier system comprising:
a multi-stage power amplifier including a driver stage; and
a programmable low dropout regulator including an output that powers the driver stage with a programmable output voltage that is programmable to a plurality of different voltage levels, the programmable low dropout regulator including an error amplifier, a regulation field-effect transistor including a gate electrically connected to an output of the error amplifier and a drain electrically connected to the output of the programmable low dropout regulator, a feedback circuit configured to provide feedback to a first input of the error amplifier based on a voltage level of the programmable output voltage, an output capacitor electrically connected to the output of the programmable low dropout regulator, and an alternative discharge circuit configured to activate to discharge the output capacitor in response to programming the programmable output voltage from a high voltage level to a low voltage level.

10. The power amplifier system of claim 9 further comprising a transceiver configured to generate a control signal operable to control the voltage level of the programmable output voltage.

11. The power amplifier system of claim 10 wherein the programmable low dropout regulator further includes a reference voltage generator configured to generate a reference voltage for a second input of the error amplifier, the reference voltage generator configured to receive the control signal.

12. The power amplifier system of claim 10 wherein the feedback circuit includes a resistor having a programmable resistance controlled by the control signal.

13. The power amplifier system of claim 9 wherein the alternative discharge circuit includes a comparator configured to compare the programmable output voltage to a trigger voltage, and to selectively activate an electrical path from the output of the programmable low dropout regulator to a first voltage based on the comparison.

14. The power amplifier system of claim 13 wherein the electrical path includes a discharge control circuit and a discharge field-effect transistor electrically connected in series between the output of the programmable low dropout regulator and the first voltage.

15. The power amplifier system of claim 9 wherein the multi-stage power amplifier further includes an output stage, the power amplifier system further including a DC-to-DC converter that powers the output stage.

16. The power amplifier system of claim 9 wherein the multi-stage power amplifier further includes an output stage, the power amplifier system further including an envelope tracker that powers the output stage.

17. A method of voltage regulation in a programmable low dropout regulator, the method comprising:
controlling a gate of a regulation field-effect transistor using an error amplifier;
regulating an output voltage provided at an output node using the regulation field-effect transistor;
generating a feedback signal for a first input of the error amplifier based on a voltage level of the output voltage using a feedback circuit;
stabilizing the output voltage using an output capacitor;
programming the output voltage from a high voltage level to a low voltage level; and
activating an alternative discharge circuit to discharge the output capacitor in response to programming the output voltage from the high voltage level to the low voltage level.

18. The method of claim 17 further comprising powering a driver stage of a power amplifier using the output voltage.

19. The method of claim 17 further comprising comparing the programmable output voltage of the low dropout regulator to a trigger voltage using a comparator, and selectively activating an electrical path from the output node to a first voltage through the alternative discharge circuit based on the comparison.

20. The method of claim 19 further comprising programming the voltage level of the output voltage using a control signal, and adjusting a voltage level of the trigger voltage based on the control signal.

21. The programmable low dropout regulator of claim 1 wherein the alternative discharge circuit is configured to selectively activate an electrical path from the output node to the first voltage to discharge the capacitor.

Assignees

• Skyworks Solutions Inc

Inventors

• Gebeyehu Netsanet
• Shi Ying
• Feng Jinghang

Classifications

• G05F1/56 Primary

  using semiconductor devices in series with the load as final control devices (G05F1/461 takes precedence) · CPC title

• H03F2200/451

  the amplifier being a radio frequency amplifier · CPC title

• H03F2200/411

  the output amplifying stage of an amplifier comprising two power stages · CPC title

• H03F2200/336

  A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit · CPC title

• H03F2200/102

  A non-specified detector of a signal envelope being used in an amplifying circuit · CPC title