The LM25116 is a synchronous buck controller intended for step-down regulator
applications from a high voltage or widely varying input supply. The control method is based upon
current mode control using an emulated current ramp. Current mode control provides inherent line
feedforward, cycle-by-cycle current limiting and ease of loop compensation. The use of an emulated
control ramp reduces noise sensitivity of the pulse-width modulation circuit, allowing reliable
control of very small duty cycles necessary in high input voltage applications. The operating
frequency is programmable from 50 kHz to 1 MHz. The LM25116 drives external high-side and low-side
NMOS power switches with adaptive dead-time control. A user-selectable diode emulation mode enables
discontinuous mode operation for improved efficiency at light load conditions. A low quiescent
current shutdown disables the controller and consumes less than 10 µA of total input current.
Additional features include a high voltage bias regulator, automatic switch-over to external bias
for improved efficiency, thermal shutdown, frequency synchronization, cycle-by-cycle current limit
and adjustable line undervoltage lockout. The device is available in a power enhanced 20-pin HTSSOP
package featuring an exposed die attach pad to aid thermal dissipation.
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