Overview
The UC3843J is a fixed frequency current-mode PWM (Pulse Width Modulation) controller produced by Unitrode, now part of Texas Instruments. This integrated circuit is specifically designed for off-line and DC-to-DC converter applications, requiring minimal external components. It is renowned for its precise duty cycle control, high gain error amplifier, and current sensing comparator, making it ideal for driving power MOSFETs.
Key Specifications
| Parameter | Symbol | Min | Max | Unit |
|---|---|---|---|---|
| DC Supply Voltage | VCC | 12 | 25 | V |
| Output Current | Io | -1.0 | 1.0 | A |
| Output Energy (Capacitive Load per Cycle) | 5.0 | µJ | ||
| Error Amp Output Sink Current | Ioe | 10 | mA | |
| Current Sense and Voltage Feedback Inputs | VIN | -0.3 | 5.5 | V |
| Maximum Power Dissipation @TA=25°C | PD | 0.862 | W | |
| Thermal Resistance, Junction-to-Air | RθJA | 145 | °C/W | |
| Maximum Operating Junction Temperature | TJ | 150 | °C | |
| Storage Temperature Range | TSTG | -65 | 150 | °C |
| Operating Temperature | TA | 0 | 70 | °C |
| Reference Output Voltage | VREF | 4.9 | 5.1 | V |
| Line Regulation | RegLINE | 20 | mV | |
| Load Regulation | RegLOAD | 25 | mV | |
| Total Output Variation over Line, Load, Temperature | VFINAL | 4.82 | 5.18 | V |
Key Features
- Fixed Frequency Current-Mode Operation: The UC3843J operates at a fixed frequency, allowing for precise control over the duty cycle and current sensing.
- High Gain Error Amplifier: Provides high gain for accurate voltage feedback and control.
- Current Sensing Comparator: Enables cycle-by-cycle current limiting and protects against overcurrent conditions.
- High Current Totem Pole Output: Capable of sourcing and sinking peak currents up to 1.0 A, ideal for driving power MOSFETs.
- Internally Trimmed Bandgap Reference: Offers a stable reference voltage, ensuring consistent performance across various operating conditions.
- Undervoltage Lockout with Hysteresis: Prevents the IC from operating below a certain voltage threshold, ensuring reliable startup and operation.
- Low Start-Up Current: Minimizes power consumption during startup, making it efficient for various applications.
- Double Pulse Suppression: Reduces the risk of double pulsing, which can occur in certain switching configurations.
- Optimized for Offline Converters: Designed to efficiently manage power sequencing in offline converters and DC-to-DC regulators.
Applications
- Wireless Base Station Power: Used in power supplies for wireless base stations due to its high efficiency and reliability.
- Telecom and Datacom Power: Suitable for power supplies in telecommunications and data communications equipment.
- Industrial Power Systems: Employed in various industrial power systems requiring robust and efficient power management.
- PC Power Supplies: Commonly used in PC power supplies for its ability to manage high current and voltage efficiently).
Q & A
- What is the UC3843J used for?
The UC3843J is a fixed frequency current-mode PWM controller used in off-line and DC-to-DC converter applications.
- What is the maximum operating frequency of the UC3843J?
The UC3843J can operate up to a maximum frequency of 500 kHz.
- What is the maximum output current of the UC3843J?
The UC3843J can source and sink peak currents up to 1.0 A.
- What are the key features of the UC3843J's error amplifier?
The error amplifier has high gain and is used for accurate voltage feedback and control.
- How is the oscillator frequency programmed in the UC3843J?
The oscillator frequency is programmed by connecting a resistor (RT) to VREF and a capacitor (CT) to ground. The frequency can be calculated using the formula Fosc (kHz) = 1.72 / (RT (k) * CT (pf)).
- What protective features does the UC3843J have?
The UC3843J includes input and reference under-voltage lockouts with hysteresis, cycle-by-cycle current limiting, and double pulse suppression.
- What is the operating temperature range of the UC3843J?
The operating temperature range is from 0°C to 70°C.
- What is the storage temperature range of the UC3843J?
The storage temperature range is from -65°C to 150°C.
- What are some common applications of the UC3843J?
Common applications include wireless base station power, telecom and datacom power, industrial power systems, and PC power supplies.
- How does the UC3843J manage duty cycle control?
The UC3843J features a trimmed oscillator for precise duty cycle control, and the duty cycle can be programmed using the RT and CT components.
