5962-8670403VXA

5962-8670403VXA 1 Features

• Optimized for off-line and DC-to-DC converters • Low start-up current (< 1 mA) • Automatic feedforward compensation • Pulse-by-pulse current limiting • Enhanced load-response characteristics • Undervoltage lockout with hysteresis • Double-pulse suppression • High-current totem-pole output • • Up to 500-kHz operation • Error amplifier with low output resistanceInternally trimmed bandgap reference

5962-8670403VXA 3 Description

internallyThe UCx84x series of control integrated circuitsprovide the features that are necessary to implementoff-line or DC-to-DC fixed-frequency current-modecontrol schemes, with a minimum number of externalimplemented circuitscomponents. Theinclude an undervoltage lockout (UVLO), featuring astart-up current of less than 1 mA, and a precisionreference trimmed for accuracy at the error amplifierinput. Other internal circuits include logic to ensurelatched operation, a pulse-width modulation (PWM)comparator that also provides current-limit control,and a totem-pole output stage that is designed tosource or sink high-peak current. The output stage,suitable for driving N-channel MOSFETs, is low whenit is in the off state.temperatureThe UCx84x family offers a variety of packageoptions,range options, choice ofmaximum duty cycle, and choice of turnon and turnoffthresholds and hysteresis ranges. Devices with higherturnon or turnoff hysteresis are ideal choices for off-line power supplies, while the devices with a narrowerhysteresis range are suited for DC-DC applications.The UC184x devices are specified for operation from–55°C to 125°C, the UC284x series is specified foroperation from –40°C to 85°C, and the UC384x seriesis specified for operation from 0°C to 70°C.Device Information(1)Simplified Application

5962-8670403VXA 2 Applications

• Switching regulators of any polarity • Transformer-coupled DC-DC converters