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UC3843 DIP-8 Current-Mode PWM Controller IC 50% Duty Cycle (5-Pack)
UC3843 DIP-8 Current-Mode PWM Controller IC 50% Duty Cycle (5-Pack)
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UC3843 DIP-8 Current-Mode PWM Controller IC - 50% Max Duty Cycle (5-Pack)
The UC3843 is a current-mode PWM controller in a DIP-8 through-hole package, featuring a 50% maximum duty cycle clamp and low UVLO thresholds (8.5V on / 7.6V off). The through-hole DIP-8 package makes it ideal for prototyping, repair work, and breadboard-based SMPS development. Functionally identical to the UC3845 (SOP-8 SMD version).
Key Specifications
| Parameter | Value |
|---|---|
| Part Number | UC3843 |
| Package | DIP-8 (through-hole) |
| Topology | Current-mode PWM (fixed frequency) |
| Max Duty Cycle | 50% (internal clamp) |
| Max Oscillator Frequency | 500kHz |
| Gate Drive Output | 1A peak (totem-pole) |
| UVLO Thresholds | 8.5V on / 7.6V off |
| Reference Voltage | 5V (2% accuracy) |
| Current Sense Threshold | 1V (cycle-by-cycle OCP) |
| Operating Temperature | 0C to +70C |
| Quantity | 5 pieces |
UC3843 Pin Configuration (DIP-8)
| Pin | Name | Function |
|---|---|---|
| 1 | COMP | Error amplifier output / compensation |
| 2 | VFB | Voltage feedback input |
| 3 | ISENSE | Current sense input (1V threshold) |
| 4 | RT/CT | Oscillator timing resistor/capacitor |
| 5 | GND | Ground |
| 6 | OUTPUT | Gate drive output (1A totem-pole) |
| 7 | VCC | Supply voltage (8.5V-30V) |
| 8 | VREF | 5V reference output |
Why Choose UC3843?
- DIP-8 Through-Hole - Breadboard-friendly for prototyping and repair
- 50% Duty Cycle Clamp - Safe for forward converter transformer volt-second balance
- Low UVLO - 8.5V startup suits lower-voltage auxiliary supplies
- 1A Gate Drive - Directly drives MOSFETs up to ~10nC gate charge
- Industry Standard - Widely used in SMPS repair; extensive reference designs
Typical Applications
- Single-ended forward converter SMPS
- Flyback converter with lower UVLO requirement
- DC-DC converter prototyping on breadboard
- SMPS repair replacement (monitors, adapters, industrial PSU)
- Boost converter controller
FAQ
Q: How do I set the oscillator frequency for UC3843? Frequency = 1.72 / (RT x CT). For 65kHz: RT = 10k ohm, CT = 2.7nF. For 100kHz: RT = 10k ohm, CT = 1.8nF.
Q: Can UC3843 replace UC3842 in an existing design? Only if the design operates below 50% duty cycle. UC3843 will clamp duty cycle at 50%; UC3842 allows up to 100%. Check the original design's maximum duty cycle before substituting.
Package Contents
- 5x UC3843 DIP-8 Current-Mode PWM Controller IC
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