A circuit for generating a ripple voltage for a ripple based constant-on-time DC-DC converter, the circuit comprising: a ripple voltage output; a first charging circuit connected to the ripple voltage output; a second charging circuit connected to the ripple voltage output; a charge control circuit configured to charge the first charging circuit and the second charging circuit out-of-phase from each other in response to an on signal from the ripple based constant-on-time DC-DC converter; wherein the charge control circuit includes a ramp bias generator and a clock generator, the ramp bias generator comprising two switchable current sources (370, 372), the switchable current sources configured to control the voltage at a charge node of the ramp bias generator in response to the on signal from the ripple based constant-on-time DC-DC converter, the clock generator configured to generate a first ripple ramp control signal in response to the on signal from the ripple based constant-on-time DC-DC converter and to generate a second ripple ramp control signal in response to the on signal from the ripple based constant-on-time DC-DC converter, wherein the first ripple ramp control signal and the second ripple ramp control signal are configured to be out-of-phase from each other, such that the second charging circuit is exposed to a reference voltage while the first charging circuit is exposed to the charge node of the ramp bias generator in response to the first ripple ramp control signal and the second ripple ramp control signal, and such that the first charging circuit is exposed to the reference voltage while the second charging circuit is exposed to the charge node of the ramp bias generator in response to the first ripple ramp control signal and the second ripple ramp control signal; wherein the voltage of the first charging circuit and the voltage of the second charging circuit are configured to be provided at the ripple voltage output as the ripple voltage, such that the voltage of only one of the charging circuits is presented at the ripple voltage output at any one time as the ripple voltage. a ripple voltage output; a first charging circuit connected to the ripple voltage output; a second charging circuit connected to the ripple voltage output; a charge control circuit configured to charge the first charging circuit and the second charging circuit out-of-phase from each other in response to an on signal from the ripple based constant-on-time DC-DC converter; wherein the charge control circuit includes a ramp bias generator and a clock generator, the ramp bias generator comprising two switchable current sources (370, 372), the switchable current sources configured to control the voltage at a charge node of the ramp bias generator in response to the on signal from the ripple based constant-on-time DC-DC converter, the clock generator configured to generate a first ripple ramp control signal in response to the on signal from the ripple based constant-on-time DC-DC converter and to generate a second ripple ramp control signal in response to the on signal from the ripple based constant-on-time DC-DC converter, wherein the first ripple ramp control signal and the second ripple ramp control signal are configured to be out-of-phase from each other, such that the second charging circuit is exposed to a reference voltage while the first charging circuit is exposed to the charge node of the ramp bias generator in response to the first ripple ramp control signal and the second ripple ramp control signal, and such that the first charging circuit is exposed to the reference voltage while the second charging circuit is exposed to the charge node of the ramp bias generator in response to the first ripple ramp control signal and the second ripple ramp control signal; wherein the voltage of the first charging circuit and the voltage of the second charging circuit are configured to be provided at the ripple voltage output as the ripple voltage, such that the voltage of only one of the charging circuits is presented at the ripple voltage output at any one time as the ripple voltage.