Overview
The UC3843N is a fixed frequency current-mode PWM (Pulse Width Modulation) controller produced by Fairchild Semiconductor. It is specifically designed for off-line and DC to DC converter applications, requiring minimal external components. This integrated circuit features a trimmed oscillator for precise duty cycle control, a temperature-compensated reference, a high gain error amplifier, a current sensing comparator, and a high current totem-pole output for driving a Power MOSFET.
Key Specifications
| Parameter | Symbol | Value | Unit |
|---|---|---|---|
| Supply Voltage | VCC | 30 | V |
| Output Current | IO | ±1 | A |
| Analog Inputs (Pin 2,3) | V(ANA) | -0.3 to 6.3 | V |
| Error Amp Output Sink Current | ISINK (E.A) | 10 | mA |
| Power Dissipation at TA≤25°C (8DIP) | PD | 1200 | mW |
| Storage Temperature Range | TSTG | -65 ~ +150 | °C |
| Oscillation Frequency | f | 47 to 57 | kHz |
| Maximum Duty Cycle | D(Max) | 95 to 100 | % |
| Start Threshold | VTH(ST) | 7.8 to 9.0 | V |
| Minimum Operating Voltage (After Turn On) | VOPR(MIN) | 7.0 to 8.2 | V |
Key Features
- Fixed Frequency Current-Mode PWM Controller
- Low Start Up Current
- Maximum Duty Clamp
- UVLO (Under-Voltage Lockout) with Hysteresis
- Operating Frequency up to 500kHz
- Trimmed Oscillator for Precise Duty Cycle Control
- Temperature-Compensated Reference
- High Gain Error Amplifier
- Current Sensing Comparator
- High Current Totem-Pole Output for Driving a Power MOSFET
Applications
The UC3843N is designed for various power conversion applications, including:
- Off-Line Converters
- DC to DC Converters
- Step-Up, Step-Down, and Step-Up/Step-Down Converters
- High Efficiency Power Supplies
Q & A
- What is the primary function of the UC3843N?
The UC3843N is a fixed frequency current-mode PWM controller designed for off-line and DC to DC converter applications.
- What is the operating frequency range of the UC3843N?
The UC3843N operates at frequencies up to 500kHz.
- What are the key features of the UC3843N?
Key features include low start-up current, maximum duty clamp, UVLO with hysteresis, and a high current totem-pole output.
- What is the supply voltage range for the UC3843N?
The supply voltage range is up to 30V.
- What is the maximum duty cycle of the UC3843N?
The maximum duty cycle is 95% to 100%.
- What are the typical applications of the UC3843N?
Typical applications include off-line converters, DC to DC converters, and high efficiency power supplies.
- What is the storage temperature range for the UC3843N?
The storage temperature range is -65°C to +150°C.
- How does the UVLO feature work in the UC3843N?
The UVLO feature ensures the device operates only when the supply voltage exceeds a certain threshold (7.8V to 9.0V) and has hysteresis to prevent oscillations.
- What is the power dissipation at TA≤25°C for the 8DIP package?
The power dissipation at TA≤25°C for the 8DIP package is 1200mW.
- Can the UC3843N operate at 100% duty cycle?
Yes, the UC3843N can operate within a 100% duty cycle.
