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
Datasheet
