A synchronous buck converter having an improved transient response during
output current includes a first switching transistor connected between an
input node and a first node, a second switching transistor connected
between the first node and a second node, a series inductor connected
between the first node and an output node, an output capacitor connected
between the output node and the second node, a first driver circuit
operative to turn the first switching transistor one and off according to
a variable duty cycle determined by an error signal representing the
difference between the voltage output of the converter and a reference
voltage, a sensing circuit operative to provide a control signal output
when the duty cycle for the first switching transistor is zero, a second
drive circuit responsive to the control signal output of the sensing
circuit to turn off the second switching transistor and a second sensing
circuit operative to provide a second control signal when a dissipating
current of the inductor is zero, wherein the second drive circuit is
responsive to the second control signal to turn the second switching
transistor on when the dissipating current of the inductor is zero.