KA3844B Fairchild SMPS Controller Data Sheet

Download Datasheet for Fairchild Semiconductor KA3844B Fixed Frequency Current-Mode PWM Controller [12 pages Rev.5.0 2000 pdf/zip]

SKU: KA3844BFAIRCHILDDS2000REV5 Category: Brand:

Description

The KA3844B is a fixed frequency current-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 Ideally suited for driving a power MOSFET. Protection circuity Includes built in under-voltage lockout and current limiting.
The KA3844B have UVLO thresholds of 16V (on) and 10V (off).
The KA3844B 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 (PINOUT)

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS
– Reference 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 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