A switch mode power supply (SMPS) controller using hysteretic control in combination with pulse-width modulation control, said controller comprising: a hysteretic control circuit comprising a first and second hysteretic comparator (430, 432), wherein an inverting input of the first hysteretic comparator and a non-inverting input of the second hysteretic comparator are configured to receive a reference voltage (VREF) and a non-inverting input of the first hysteretic comparator and an inverting input of the second hysteretic comparator are configured to receive a feedback voltage representing a load side output voltage of a switch mode power supply (SMPS), a first output of the hysteretic control circuit coupled with an output of the second hysteretic comparator for controlling a high side hysteretic demand, and a second output of the hysteretic control circuit coupled with an output of the first hysteretic comparator for controlling a low side hysteretic disable; a PWM error generator having a first input configured to receive the reference voltage (VREF), a second input configured to receive the feedback voltage, a third input configured to be couplable to a current sense circuit, and a third output for controlling PWM demand; and a power circuit driver having a high side power control output, and a low side power control output, the HS and LS power control outputs are adapted to drive power switches of a switch mode power supply (SMPS), the third output of the PWM error generator is coupled to the power circuit driver for control thereof, and the first and second outputs of the hysteretic control circuit are coupled to the power circuit driver for further control thereof; the PWM error generator third output is arranged to control the power circuit driver to make the feedback voltage equal to the reference voltage unless a difference between the feedback voltage and the reference voltage is greater than at least a predetermined value, wherein the switch mode power supply (SMPS) controller is configured such that if the feedback voltage is greater than the reference voltage by at least the predetermined value, then the hysteretic control circuit forces the HS and LS power control outputs to an off-state, if the feedback voltage is less than the reference voltage by at least the predetermined value, then the hysteretic control circuit turns on the HS and turns off the LS power control output, and otherwise the PWM error generator controls the HS and LS power control outputs so as to force the difference between the reference voltage and the feedback voltage to zero over a certain time period. a hysteretic control circuit comprising a first and second hysteretic comparator (430, 432), wherein an inverting input of the first hysteretic comparator and a non-inverting input of the second hysteretic comparator are configured to receive a reference voltage (VREF) and a non-inverting input of the first hysteretic comparator and an inverting input of the second hysteretic comparator are configured to receive a feedback voltage representing a load side output voltage of a switch mode power supply (SMPS), a first output of the hysteretic control circuit coupled with an output of the second hysteretic comparator for controlling a high side hysteretic demand, and a second output of the hysteretic control circuit coupled with an output of the first hysteretic comparator for controlling a low side hysteretic disable; a PWM error generator having a first input configured to receive the reference voltage (VREF), a second input configured to receive the feedback voltage, a third input configured to be couplable to a current sense circuit, and a third output for controlling PWM demand; and a power circuit driver having a high side power control output, and a low side power control output, the HS and LS power control outputs are adapted to drive power switches of a switch mode power supply (SMPS), the third output of the PWM error generator is coupled to the power circuit driver for control thereof, and the first and second outputs of the hysteretic control circuit are coupled to the power circuit driver for further control thereof; the PWM error generator third output is arranged to control the power circuit driver to make the feedback voltage equal to the reference voltage unless a difference between the feedback voltage and the reference voltage is greater than at least a predetermined value, wherein the switch mode power supply (SMPS) controller is configured such that if the feedback voltage is greater than the reference voltage by at least the predetermined value, then the hysteretic control circuit forces the HS and LS power control outputs to an off-state, if the feedback voltage is less than the reference voltage by at least the predetermined value, then the hysteretic control circuit turns on the HS and turns off the LS power control output, and otherwise the PWM error generator controls the HS and LS power control outputs so as to force the difference between the reference voltage and the feedback voltage to zero over a certain time period. if the feedback voltage is less than the reference voltage by at least the predetermined value, then the hysteretic control circuit turns on the HS and turns off the LS power control output, and otherwise the PWM error generator controls the HS and LS power control outputs so as to force the difference between the reference voltage and the feedback voltage to zero over a certain time period.