Overview
The UC3843D is a fixed frequency current-mode Pulse Width Modulation (PWM) controller, designed and manufactured by Fairchild Semiconductor (now part of ON Semiconductor). This integrated circuit is specifically tailored for off-line and DC-to-DC converter applications, requiring minimal external components. The UC3843D 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 power MOSFETs. It is widely used in various power supply and converter applications due to its robust and efficient design.
Key Specifications
| Parameter | Symbol | Value | Unit |
|---|---|---|---|
| Supply Voltage | VCC | 30 | V |
| Output Current | IO | ±1 | A |
| Analog Inputs | V(ANA) | -0.3 to 6.3 | V |
| Error Amp Output Sink Current | ISINK (E.A) | 10 | mA |
| Power Dissipation at 8DIP | PD | 1200 | mW |
| Power Dissipation at 8SOP | PD | 460 | mW |
| Power Dissipation at 14SOP | PD | 680 | mW |
| Storage Temperature Range | TSTG | -65 ~ +150 | °C |
| Operating Frequency | f | Up to 500 kHz | kHz |
| UVLO Thresholds | VTH(ST) | 8.5V (on), 7.9V (off) | V |
Key Features
- Current-mode PWM controller with fixed frequency
- Trimmed oscillator for precise duty cycle control
- Temperature-compensated reference
- High-gain error amplifier
- Current sensing comparator
- High-current totem-pole output for driving power MOSFETs
- Low startup current (<1 mA)
- Pulse-by-pulse current limiting
- Low output resistance
- Double pulse suppression
- Maximum duty clamp
- UVLO with hysteresis
- Operating frequency up to 500 kHz
- Optimized for off-line and DC-to-DC converters
- Automatic feed-forward compensation
- Internally trimmed bandgap reference
Applications
- Switch-mode power supplies (SMPS)
- Transformer-coupled DC-to-DC converters
- Electronic power supplies
- Battery drain circuits
- Load machines
- Switching regulators with any polarity
Q & A
- What is the UC3843D used for?
The UC3843D is used as a current-mode PWM controller in off-line and DC-to-DC converter applications.
- What are the UVLO thresholds for the UC3843D?
The UC3843D has UVLO thresholds of 8.5V (on) and 7.9V (off).
- What is the maximum operating frequency of the UC3843D?
The UC3843D can operate at frequencies up to 500 kHz.
- What type of output does the UC3843D have?
The UC3843D has a high-current totem-pole output for driving power MOSFETs.
- What are the typical applications of the UC3843D?
Typical applications include SMPS, transformer-coupled DC-to-DC converters, electronic power supplies, and switching regulators.
- What is the startup current of the UC3843D?
The startup current of the UC3843D is less than 1 mA.
- Does the UC3843D support 100% duty cycle operation?
Yes, the UC3843D can operate within a 100% duty cycle.
- What is the power dissipation of the UC3843D in different packages?
The power dissipation is 1200 mW for 8DIP, 460 mW for 8SOP, and 680 mW for 14SOP.
- What is the storage temperature range for the UC3843D?
The storage temperature range is -65°C to +150°C.
- How do you configure the oscillator in the UC3843D?
The oscillator can be configured by connecting the right value of capacitor and resistor to the Rt/Ct pins. Recommended values are between 470 pF to 4.7 nF for the capacitor and 5 kΩ to 100 kΩ for the resistor.
