UC1525A/27A
UC2525A/27A
UC3525A/27A
RegulatingPulseWidthModulators
FEATURES
•8to35VOperation
•5.1VReferenceTrimmedto±1%
•100Hzto500kHzOscillatorRange
•SeparateOscillatorSyncTerminal
•AdjustableDeadtimeControl
•InternalSoft-Start
•Pulse-by-PulseShutdown
•InputUndervoltageLockoutwithHysteresis
•LatchingPWMtoPreventMultiplePulses
•DualSource/SinkOutput
Drivers
15
12
3
6
5
7
9
1
2
8
10ReferenceRegulator16
UVLOLockout4
OSC
3kΩ
5kΩ50µAPWMLatchFlipFlop
13141113
11
14
UC1527AOutputStageUC1525AOutputStage
COMPS
SR+VIN
GROUND
SYNC
RT
CT
DISCHARGE
COMPENSATION
INVINPUT
NIINPUT
SOFTSTART
SHUTDOWNOUTPUTBOUTPUTAVCOUTPUTBOUTPUTAVC
NOR
NOR
OR
ORVREFErrorAmpVREFOSCOUT
TointernalcircuitryBLOCKDIAGRAM
SLUS191B-February1997-RevisedJune2005DESCRIPTION
TheUC1525A/1527Aseriesofpulsewidthmodulatorintegratedcircuitsarede-
signedtoofferimprovedperformanceandloweredexternalpartscountwhen
UC1842A-EP, UC1843A-EP, UC1844A-EP, UC1845A-EP
CURRENT-MODE PWM CONTROLLER
SGLS134B – SEPTEMBER 2002 – REVISED APRIL 2003
1POST OFFICE BOX 655303 •
DALLAS, TEXAS 75265DControlled Baseline
– One Assembly/Test Site, One Fabrication
Site
DExtended Temperature Performance of
–55°C to 125°C
DEnhanced Diminishing Manufacturing
Sources (DMS) Support
DEnhanced Product Change Notification
DQualification Pedigree†
DOptimized for Off-line and DC to DC
Converters
DLow Start Up Current (<0.5 mA)
DTrimmed Oscillator Discharge Current
†Component qualification in accordance with JEDEC and industry
standards to ensure reliable operation over an extended
temperature range. This includes, but is not limited to, Highly
Accelerated Stress Test (HAST) or biased 85/85, temperature
cycle, autoclave or unbiased HAST, electromigration, bond
intermetallic life, and mold compound life. Such qualification
UC1861-1868
UC2861-2868
UC3861-3868
SLUS289 - OCTOBER 1998FEATURES
•Controls Zero Current Switched (ZCS)
or Zero Voltage Switched (ZVS)Quasi-Resonant Converters
•Zero-Crossing Terminated One-Shot
Timer
•Precision 1%, Soft-Started 5V
Reference
•Programmable Restart Delay
Following Fault
•Voltage-Controlled Oscillator (VCO)
with Programmable Minimum andMaximum Frequencies from 10kHz to1MHz
•Low Start-Up Current (150µA typical)
•Dual 1 Amp Peak FET Drivers
•UVLOOption for Off-Line or DC/DC
ApplicationsDESCRIPTION
TheUC1861-1868familyofICsisoptimizedforthecontrolofZeroCurrent
SwitchedandZeroVoltageSwitchedquasi-resonantconverters.Differ-
encesbetweenmembersofthisdevicefamilyresultfromthevariouscom-
binationsofUVLOthresholdsandoutputoptions.Additionally,the
one-shotpulsesteeringlogicisconfiguredtoprogrameitheron-timefor
ZCSsystems(UC1865-1868),oroff-timeforZVSapplications(UC1861-
UC1861-1868
UC2861-2868
UC3861-3868
10/98FEATURES
•Controls Zero Current Switched (ZCS)or Zero Voltage Switched (ZVS)Quasi-Resonant Converters
•Zero-Crossing Terminated One-ShotTimer
•Precision 1%, Soft-Started 5VReference
•Programmable Restart DelayFollowing Fault
•Voltage-Controlled Oscillator (VCO)with Programmable Minimum andMaximum Frequencies from 10kHz to1MHz
•Low Start-Up Current (150µA typical)
•Dual 1 Amp Peak FET Drivers
•UVLO Option for Off-Line or DC/DCApplicationsDESCRIPTION
TheUC1861-1868familyofICsisoptimizedforthecontrolofZeroCur-
rentSwitchedandZeroVoltageSwitchedquasi-resonantconverters.Dif-
ferencesbetweenmembersofthisdevicefamilyresultfromthevarious
combinationsofUVLOthresholdsandoutputoptions.Additionally,the
one-shotpulsesteeringlogicisconfiguredtoprogrameitheron-timefor
ZCSsystems(UC1865-1868),oroff-timeforZVSapplications(UC1861-
