UC3844 Fairchild SMPS Controller Data Sheet

Download Datasheet for Fairchild Semiconductor UC3844 SMPS Controller [12 pages Rev.1.0.1 2002 pdf/zip]

SKU: UC3844FairchildDS2002REV101 Category: Brand:

Description

The UC3844 are fixed frequencycurrent-mode PWM controller. They are specially designed for Off-Line and DC to DC converter applications with minimum external components. These integrated circuits feature a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator and a high current totempole output for driving a Power MOSFET.
The UC3844 have UVLO thresholds of 16V (on) and 10V (off).
The UC3844 can operate with 50% duty cycle.

FEATURES
– Low Start up Current
– Maximum Duty Clamp
– UVLO With Hysteresis
– Operating Frequency up to 500KHz

DATASHEET CONTAINS:

INTERNAL BLOCK DIAGRAM

UC3844 PINOUT

ABSOLUTE MAXIMUM RATINGS

POWER DISSIPATION CURVE

THERMAL DATA

PIN ARRAY

ELECTRICAL CHARACTERISTICS
– Reference Section
– Oscillator Section
– Error Amplifier Section
– Current Sense Section
– Output Section
– Under-Voltage Lockout Section
– PWM Section
– Total Standby Current

Figure 1. Open Loop Test Circuit
Figure 2. Under Voltage Lockout
Figure 3. Error Amp Configuration
Figure 4. Current Sense Circuit
Figure 5. Oscillator Waveforms and Maximum Duty Cycle
Figure 6. Oscillator Dead Time & Frequency
Figure 7. Timing Resistance vs Frequency
Figure 8. Shutdown Techniques
Figure 9. Slope Compensation
Figure 10. Temperature Drift (Vref)
Figure 11. Temperature Drift (Ist)
Figure 12. Temperature Drift (Icc)

MECHANICAL DIMENSIONS

ORDERING INFORMATION