ZHCS571I August 2010 – April 2018 LM5119
PRODUCTION DATA.
A fully synchronous buck regulator implemented with a free-wheel MOSFET rather than a diode has the capability to sink current from the output in certain conditions such as light load, overvoltage, or prebias start-up. The LM5119 provides a diode emulation feature that can be enabled to prevent reverse (drain to source) current flow in the low-side free-wheel MOSFET. When configured for diode emulation, the low-side MOSFET is disabled when reverse current flow is detected. The benefit of this configuration is lower power loss at no load or light load conditions and the ability to turn on into a prebiased output without discharging the output. The diode emulation mode allows for start-up into prebiased loads, because it prevents reverse current flow as the soft-start capacitor charges to the regulation level during start-up. The negative effect of diode emulation is degraded light load transient response times. Enabling the diode emulation feature is recommended and allows discontinuous conduction operation. The diode emulation feature is configured with the DEMB pin. To enable diode emulation, connect the DEMB pin to ground or leave the pin floating. If continuous conduction operation is desired, the DEMB pin must be tied to either VCC1 or VCC2.