A method comprising: providing from a charge pump power supply a power supply voltage to a power supply input of a power amplifier having an audio input configured to receive an audio input signal, and an audio output configured to generate an analog audio signal (V OUT) for playback at a transducer device having a load impedance (R L) and configured to be coupled to the audio output via an electrical terminal; the method further comprising: detecting a peak amplitude (V ripple) of a voltage ripple of the power supply voltage (V SUPPLY) in response to a transition of the analog audio output signal (V OUT); detecting a peak amplitude (V pk) of a change in a digital audio input signal (DIG_IN) that causes the transition of the analog audio output signal (V OUT), wherein the digital audio input is input to a digital-to-analog conversion circuit coupled to the power amplifier and configured to convert a digital audio input signal (DIG_IN) into the analog audio input signal; and estimating a value of the load impedance (R L) using the relationship V ripple =V pk R switch /R L, wherein V ripple is the peak amplitude of the voltage ripple, V pk is the peak amplitude of the change in the digital audio input signal, and R switch is an input series resistance of the the charge pump power supply. providing from a charge pump power supply a power supply voltage to a power supply input of a power amplifier having an audio input configured to receive an audio input signal, and an audio output configured to generate an analog audio signal (V OUT) for playback at a transducer device having a load impedance (R L) and configured to be coupled to the audio output via an electrical terminal; the method further comprising: detecting a peak amplitude (V ripple) of a voltage ripple of the power supply voltage (V SUPPLY) in response to a transition of the analog audio output signal (V OUT); detecting a peak amplitude (V pk) of a change in a digital audio input signal (DIG_IN) that causes the transition of the analog audio output signal (V OUT), wherein the digital audio input is input to a digital-to-analog conversion circuit coupled to the power amplifier and configured to convert a digital audio input signal (DIG_IN) into the analog audio input signal; and estimating a value of the load impedance (R L) using the relationship V ripple =V pk R switch /R L, wherein V ripple is the peak amplitude of the voltage ripple, V pk is the peak amplitude of the change in the digital audio input signal, and R switch is an input series resistance of the the charge pump power supply. detecting a peak amplitude (V ripple) of a voltage ripple of the power supply voltage (V SUPPLY) in response to a transition of the analog audio output signal (V OUT); detecting a peak amplitude (V pk) of a change in a digital audio input signal (DIG_IN) that causes the transition of the analog audio output signal (V OUT), wherein the digital audio input is input to a digital-to-analog conversion circuit coupled to the power amplifier and configured to convert a digital audio input signal (DIG_IN) into the analog audio input signal; and estimating a value of the load impedance (R L) using the relationship V ripple =V pk R switch /R L, wherein V ripple is the peak amplitude of the voltage ripple, V pk is the peak amplitude of the change in the digital audio input signal, and R switch is an input series resistance of the the charge pump power supply.