UC3843 Current-Mode PWM Controller IC DIP-8
The UC3843 Current-Mode PWM Controller IC DIP-8 is a high-performance, fixed-frequency PWM controller designed for efficient DC-DC and off-line converter applications. It integrates key control features including a precision 5V reference, oscillator, error amplifier, current-sense comparator, and a high-current totem-pole output stage capable of directly driving power MOSFETs. Operating from a wide supply voltage range of 7.6V to 30V, the UC3843 provides excellent line and load regulation with current-mode operation for fast transient response and cycle-by-cycle current limiting. Its high oscillator frequency up to 500kHz allows for compact power supply designs. Encased in a standard 8-pin DIP package, it is widely used in switch-mode power supplies (SMPS), DC-DC converters, battery chargers, and motor control circuits for its reliability, efficiency, and precise performance.
Features
- Wide operating voltage range from 7.6V to 30V.
- Fixed-frequency current-mode PWM control for fast transient response.
- High oscillator frequency operation up to 500kHz.
- Totem-pole output stage capable of ±1A peak current to drive MOSFETs directly.
- Low start-up current (<1mA) for energy-efficient power-up.
- Accurate 5V ±1% reference voltage for stable system operation.
- Cycle-by-cycle current limiting for enhanced protection.
- Undervoltage lockout (UVLO) with hysteresis for reliable startup and shutdown.
- Automatic feed-forward compensation and double-pulse suppression.
- Compact 8-pin DIP package suitable for SMPS, DC-DC converters, and motor control circuits.
Pinout Configuration
| Pin No. | Symbol | Name / Function |
|---|---|---|
| 1 | COMP | Compensation input – error amplifier output used for loop compensation |
| 2 | VFB | Feedback input – voltage feedback to the internal error amplifier |
| 3 | ISENSE | Current sense input – monitors switch current for current-mode control and protection |
| 4 | RT/CT | Oscillator timing resistor/capacitor – sets the switching frequency |
| 5 | GND | Ground reference for all signals |
| 6 | OUTPUT | Output drive pin – to drive an external MOSFET or transistor |
| 7 | VCC | Supply voltage input (operating range: 7.6 V – 30 V) |
| 8 | VREF | 5 V reference output (can source up to 20 mA for biasing) |
Dimensions
Specifications
| Parameter | Descriptions |
| Product Type | Current-Mode PWM / DC-DC Converter Control IC |
| Part Number | UC3843AN |
| Datasheet | UC3843 |
| Package Type | DIP-8 |
| Operating Voltage Range | 7.6 V – 30 V |
| Reference Voltage | 5.0 V ±2% |
| Oscillation Frequency | 500 kHz |
| Output Type | Adjustable |
| Topology Supported | Buck, Boost, Flyback, Forward |
| Number of Channels | 1 |
| Switch Type | External MOSFET required |
| Undervoltage Lockout (UVLO) | 7.6 V (start) – 6.9 V (stop) |
| Output Drive Capability | ±1 A peak |
| Optimization | General-purpose PWM control, suitable for wide duty cycle designs |
| Maximum Duty Cycle | 100% |
| UVLO Thresholds (Start/Stop) | Slightly higher thresholds |
| Design Flexibility | Allows full-range duty cycles for continuous conduction designs |
| Control Method | Fixed-frequency peak current-mode PWM |
| Main Application | Forward converters, continuous-mode flyback converters |
| Operating Temperature Range | 0 °C – +70 °C |
Applications
- Switch-Mode Power Supplies (SMPS).
- DC-DC Converter Circuits.
- Battery Chargers and Power Adapters.
- LED Drivers and Lighting Power Supplies.
- Motor Speed Control Systems.
- Inverter and Converter Modules.
- Industrial and Consumer Power Electronics.
- Offline Flyback and Forward Converter Designs.
Package Contents
- 1 x UC3843 Current-Mode PWM Controller IC DIP-8