Piezo actuator driver with slew rate protection

A driver for a piezo actuator, comprising:

• a first amplifier configured to produce an output current based on an input voltage to the first amplifier;
• a second amplifier including an output, wherein the output is coupled to an input of the first amplifier, and wherein, based on an input voltage to the second amplifier, the second amplifier produces an output voltage at a predetermined slew rate;
• a voltage selection circuit configured to selectively provide as the input voltage to the second amplifier and based on a first control signal, an input voltage to the driver or a voltage that corresponds to the output current from the first amplifier being below a threshold;
• a comparator configured to compare a voltage indicative of the output current from the first amplifier to the threshold to thereby generate a compare signal responsive to the voltage indicative of the output current being less than the threshold;
• and
• a logic gate configured to gate the first control to the first amplifier based on the compare signal from the comparator to thereby control a transition of the first amplifier into a high impedance mode.

A method of driving a piezo actuator, comprising:

• driving a slew rate-controlled amplifier with a first voltage;
• responsive to a first control signal, ceasing driving the slew rate-controlled amplifier with the first voltage;
• providing a second voltage to the slew rate-controlled amplifier that is coupled to an input of a transconductance amplifier coupled to the piezo actuator, wherein the second voltage causes current produced by the transconductance amplifier to be below a threshold;
• determining whether the current from the transconductance amplifier to the piezo actuator is below the threshold;
• and
• responsive to the current from the transconductance amplifier being below the threshold, transitioning the transconductance amplifier to a high impedance mode.