UC3846 Fairchild SMPS Controller Data Sheet

Download Datasheet for Fairchild Semiconductor UC3846 SMPS Controller [10 pages Rev.5.0 2000 pdf/zip]

SKU: UC3846FAIRCHILDDS2000REV5 Category: Brand:

Description

The UC3846 control IC provides all of the necessary featuresto implement fixed frequency, current mode control schemes while maintaining a minimum external parts count. The superior performance of this technique can be measured in improved line regulation, enhanced load response characteristics, and a simpler, easier-to-design control loop.
Topological advantages include inherent pulse-by-pulse current limiting capability, automatic symmetry correction for push-pull converters, and the ability to parallel “power module”, while maintaining equal current sharing. Protection circuitry includes built-in-under-voltage lockout and programmable current limit in addition to soft-start capability. A shutdown function is also available which can initiate either a complete shutdown with automatic restart or latch the supply off. Other features include fully latched operation, double pulse suppression, deadtime adjust capability, and +/-2% trimmed bandgap reference. The UC3846 features low outputs in the OFF state.

FEATURES
– Automatic Feed Forward Compensation
– Programmable Pulse by Pulse Current Limiting
– Automatic Symmetry Correction in Push-Pull Configuration
– Enhanced Load Response Characteristics
– Parallel Operation Capability for Modulator Power Systems
– Differential Current Sense Amplifier with Common Mode Range
– Double Pulse Suppression
– 200mA Totem-Pole Outputs
– +/-2% Band gap Reference
– Under-Voltage Lockout
– Soft-Start Capability
– Shutdown Terminal
– 500KHz Operation

DATASHEET CONTAINS:

INTERNAL BLOCK DIAGRAM

UC3846 PINOUT

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS
– REFERENCE SECTION
– OSCILLATOR SECTION
– ERROR AMPLIFIER SECTION
– CURRENT SENSE AMPLIFIER SECTION
– CURRENT LIMIT ADJUST SECTION
– SHUTDOWN TERMINAL SECTION
– UNDER-VOLTAGE LOCKOUT SECTION
– OUTPUT SECTION
– TOTAL STANDBY CURRENT

Figure 1. UC3846 Oscillator Circuit
Figure 2. Error Amplifier Output Configuration
Figure 3. Parallel Operation
Figure 4. Pulse By Pulse Current Limiting
Figure 5. Current Sense Amp Connections

MECHANICAL DIMENSIONS

ORDERING INFORMATION