UC1874-1,-2
UC2874-1,-2
UC3874-1,-2 High Efficiency, Synchronous, Step-down (Buck) Controllers
FEATURES DESCRIPTION Operation to 36V Input Voltage Fixed Frequency Average Current
Mode Control Standby Mode for Improved
Efficiency at Light Load Drives External N-Channel
MOSFETs for Highest Efficiency Sleep Mode Current < 50mA Complementary 1 Amp Outputs with
Regulated Gate Drive Voltage LDO (Low Drop Out) Virtual 100%
Duty Cycle Operation The UC3874 family of synchronous step-down (Buck) regulators provides
high efficiency power conversion from an input voltage range of 4.5 to 36
volts. The UC3874 is tailored for battery powered applications such as
laptop computers, consumer products, communications systems, and
aerospace which demand high performance and long battery life. The
synchronous regulator replaces the catch diode in the standard buck
regulator with a low Rds(on) N-channel MOSFET switch allowing for
significant efficiency improvements. The high side N-channel MOSFET
switch is driven out of phase from the low side N-channel MOSFET switch
by an on-chip bootstrap circuit which requires only a single external
capacitor to develop the regulated gate drive. Fixed frequency, average
current mode control provides the regulator with inherent slope
compensation, tight regulation of the output voltage, and superior load and
line transient response. Switching frequencies up to 300kHz are possible. Non-Overlapping Gate Drives Light load efficiency is improved by a fully programmable standby mode, in
which the quiescent current consumption of the controller is significantly reduced. The reduction is achieved by disabling the MOSFET driver outputs …
