UC2874DW-1 ,2UC1874-1,-2UC2874-1,-2UC3874-1,-2High Efficiency, Synchronous, Step-down (Buck) Controllers
UC2874DW-2 ,2MAXIMUM RATINGSSupply Voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36VDI ..
UC2874DW-2 ,2BLOCK DIAGRAMUDG-95005-1SLUS286A - FEBRUARY 1998 - REVISED OCTOBER 2001UC1874-1,-2UC2874-1,-2UC3874 ..
UC2874DW-2 ,2ELECTRICAL CHARACTERISTICS: Unless otherwise stated these specifications apply for TA = –55°C to +1 ..
UC2874N-1 , High Efficiency, Synchronous, Step-down (Buck) Controllers
UC2875 ,Phase Shift Resonant ControllerMAXIMUM RATINGS CONNECTION DIAGRAMSSupply Voltage (VC, VIN) ........ 20V Dil-20 (Top View)Output Cu ..
UM91214B , Tone / Pulse Dialer
UM91214B , Tone / Pulse Dialer
UM91215D , Tone / Pulse Dialer
UM91260B , 10 MEMORY TONE /PULSE DIALER
UM91270/A , 20 MEMORY TONE/PULSE DIALER
UM91270A , 20 MEMORY TONE/PULSE DIALER
UC2874DW-1
High Efficiency, Synchronous, Step-down (Buck) Controllers
DESCRIPTIONThe UC3874 familyof synchronous step-down (Buck) regulators provides
high efficiency power conversion from an input voltage rangeof 4.5to 36
volts. The UC3874is 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 diodein the standard buck
regulator witha low Rds(on) N-channel MOSFET switch allowing for
significant efficiency improvements. The high side N-channel MOSFET
switchis driven outof phase from the low side N-channel MOSFET switch an on-chip bootstrap circuit which requires onlya single external
capacitorto develop the regulated gate drive. Fixed frequency, average
current mode control provides the regulator with inherent slope
compensation, tight regulationof the output voltage, and superior load and
line transient response. Switching frequencies up to 300kHz are possible.
Light load efficiencyis improvedbya fully programmable standby mode,in
which the quiescent current consumptionof the controlleris significantly re-
duced. The reductionis achievedby disabling the MOSFET driver outputs
and the internal oscillator when the controller has sensed that the the out-
put load current has dropped a user programmable amount from full load.
(continued)High Efficiency, Synchronous, Step-down (Buck) Controllers
FEATURES 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 Non-Overlapping Gate Drives
BLOCK DIAGRAM
UC1874-1,-2
UC2874-1,-2
UC3874-1,-2
