Using a tracking switched-mode power supply to increase efficiency of a current digital-to-analog converter-based output stage

1. A system comprising:

a current digital-to-analog converter (IDAC) configured to convert a digital input signal into an output current signal; and

a switched-mode power supply configured to provide electrical energy in the form of a supply voltage to the IDAC for operation of the IDAC, the switched-mode power supply configured to:

track a voltage signal derived from the digital input current signal; and

generate the supply voltage based on the voltage signal and a voltage headroom above the voltage signal.

2. The system of claim 1 , wherein the IDAC comprises:

a voltage-to-current filter to convert the digital input signal into a corresponding current signal; and

IDAC elements configured to convert the corresponding current signal into the output current signal.

3. The system of claim 1 , wherein the voltage signal is an output voltage signal generated from the output current signal.

4. The system of claim 1 , wherein the switched-mode power supply operates solely in a discontinuous conduction mode.

5. The system of claim 1 , wherein the switched-mode power supply is configured to track the voltage signal using a feedforward approach to determine a magnitude of the voltage signal based on the digital input signal and a slope of the digital input signal.

6. The system of claim 5 , further comprising a voltage-to-current compensator in a signal path of the IDAC in order to compensate for phase shift between the output current signal and the voltage signal.

7. The system of claim 5 , further comprising:

a first filter in a feedforward path of the switched-mode power supply; and

a second filter in a signal path of the IDAC;

wherein the first filter and the second filter compensate for phase shift between the output current signal and the voltage signal.

8. The system of claim 5 , wherein the switched-mode power supply is configured in a feedforward topology to predict a switching frequency of the switched-mode power supply based on the digital input current signal and a slope of the digital input current signal.

9. The system of claim 5 , wherein the switched-mode power supply is configured in a feedforward topology to vary a duty cycle of the switched-mode power supply based on a comparison of an output voltage of the switched-mode power supply to a reference voltage.

10. The system of claim 1 , wherein the switched-mode power supply is configured to track the voltage signal using a feedforward approach to determine a magnitude of the voltage signal based on signal outputs of a plurality of IDAC elements integral to the IDAC.

11. The system of claim 1 , wherein the switched-mode power supply is configured to track the voltage signal using:

a feedforward approach to determine a magnitude of the voltage signal based on signal outputs of a plurality of IDAC elements integral to the IDAC; and

a feedforward approach to determine a magnitude of the voltage signal based on the digital input signal and a slope of the digital input signal.

12. The system of claim 1 , wherein:

the switched-mode power supply is further configured to convert a battery voltage of a battery into the supply voltage; and

the integrated circuit further includes bypass circuitry configured to selectively bypass the switched-mode power supply to couple the battery voltage to the supply voltage.

13. The system of claim 12 , wherein the bypass circuitry is configured to couple the battery voltage to the supply voltage via a low-dropout regulator coupled between the battery voltage and the supply voltage.

14. The system of claim 12 , wherein the bypass circuitry is configured to couple the battery voltage to the supply voltage when the supply voltage is within a pre-determined magnitude of the battery voltage.

15. The system of claim 12 , wherein the bypass circuitry is configured to couple the battery voltage to the supply voltage when a bandwidth of the switched-mode power supply is insufficient to allow the supply voltage to track the voltage signal.

16. A method comprising, in a system comprising a current digital-to-analog converter (IDAC) configured to convert a digital input signal into an output current signal and a switched-mode power supply configured to provide electrical energy in the form of a supply voltage to the IDAC for operation of the IDAC:

tracking a voltage signal derived from the digital input current signal; and

generating the supply voltage based on the voltage signal and a voltage headroom above the voltage signal.

17. The method of claim 16 , further comprising:

converting the digital input signal into a corresponding current signal with a voltage-to-current filter; and

converting the corresponding current signal into the output current signal with IDAC elements.

18. The method of claim 16 , wherein the voltage signal is an output voltage signal generated from the output current signal.

19. The method of claim 16 , wherein the switched-mode power supply operates solely in a discontinuous conduction mode.

20. The method of claim 16 , further comprising tracking the voltage signal using a feedforward approach to determine a magnitude of the voltage signal based on the digital input signal and a slope of the digital input signal.

21. The method of claim 20 , further comprising compensating for phase shift between the output current signal and the voltage signal with a voltage-to-current compensator in a signal path of the IDAC.

22. The method of claim 20 , further comprising compensating for phase shift between the output current signal and the voltage signal with a first filter in a feedforward path of the switched-mode power supply and a second filter in a signal path of the IDAC.

23. The method of claim 20 , further comprising predicting a switching frequency of the switched-mode power supply based on the digital input current signal and a slope of the digital input current signal using a feedforward topology of the switched-mode power supply.

24. The method of claim 20 , further comprising varying a duty cycle of the switched-mode power supply based on a comparison of an output voltage of the switched-mode power supply to a reference voltage using a feedforward topology of the switched-mode power supply.

25. The method of claim 16 , further comprising tracking the voltage signal using a feedforward approach to determine a magnitude of the voltage signal based on signal outputs of a plurality of IDAC elements integral to the IDAC.

26. The method of claim 16 , further comprising tracking the voltage signal using:

a feedforward approach to determine a magnitude of the voltage signal based on signal outputs of a plurality of IDAC elements integral to the IDAC; and

a feedforward approach to determine a magnitude of the voltage signal based on the digital input signal and a slope of the digital input signal.

27. The method of claim 16 , wherein:

the switched-mode power supply is further configured to convert a battery voltage of a battery into the supply voltage; and

the method further comprises selectively bypassing the switched-mode power supply to couple the battery voltage to the supply voltage with bypass circuitry.

28. The method of claim 27 , further comprising coupling the battery voltage to the supply voltage via a low-dropout regulator coupled between the battery voltage and the supply voltage and integral to the bypass circuitry.

29. The method of claim 27 , further comprising coupling the battery voltage to the supply voltage when the supply voltage is within a pre-determined magnitude of the battery voltage using the bypass circuitry.

30. The method of claim 27 , further comprising coupling, using the bypass circuitry, the battery voltage to the supply voltage when a bandwidth of the switched-mode power supply is insufficient to allow the supply voltage to track the voltage signal.