ZHCSGD8A May 2017 – May 2018
PRODUCTION DATA.
With sufficient charge current, the inductor current does not cross 0 A, which is defined as CCM. The controller starts a new cycle with ramp coming up from 200 mV. As long as error amplifier output voltage is above the ramp voltage, the high-side MOSFET (HSFET) stays on. When the ramp voltage exceeds error amplifier output voltage, HSFET turns off and low-side MOSFET (LSFET) turns on. At the end of the cycle, ramp gets reset and LSFET turns off, ready for the next cycle. There is always break-before-make logic during transition to prevent cross-conduction and shoot-through. During the dead time when both MOSFETs are off, the body-diode of the low-side power MOSFET conducts the inductor current.
During CCM, the inductor current always flows and creates a fixed two-pole system. Having the LSFET turn-on when the HSFET is off keeps the power dissipation low and allows safe charging at high currents.