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UC3842A/B SOP-8 Current-Mode PWM Controller IC UC3842 SMD (5-Pack)
UC3842A/B SOP-8 Current-Mode PWM Controller IC UC3842 SMD (5-Pack)
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UC3842A/B SOP-8 Current-Mode PWM Controller IC — 500kHz
The UC3842 is a high-performance current-mode PWM controller IC in a compact SOP-8 surface-mount package. With a 500kHz maximum switching frequency, 1A peak gate drive, and built-in UVLO (undervoltage lockout), it is the go-to controller for single-ended flyback and forward converter designs in SMPS repair and new designs alike.
Key Specifications
| Parameter | Value |
|---|---|
| Part Number | UC3842A / UC3842B |
| Package | SOP-8 (SMD) |
| Supply Voltage (VCC) | 10V – 30V |
| UVLO Start Threshold | 16V (UC3842A) / 16V (UC3842B) |
| UVLO Stop Threshold | 10V (UC3842A) / 10V (UC3842B) |
| Max Oscillator Frequency | 500kHz |
| Gate Drive Output | 1A peak source/sink |
| Reference Voltage | 5V ±1% |
| Current Sense Input | 1V threshold |
| Quantity | 5 pieces |
UC3842A vs UC3842B
| Feature | UC3842A | UC3842B |
|---|---|---|
| UVLO Hysteresis | 6V | 6V |
| Max Duty Cycle | 100% | 100% |
| Temp Range | 0°C to +70°C | −40°C to +85°C |
Why Choose UC3842?
- Current-Mode Control — Inherent cycle-by-cycle current limiting for robust protection
- 1A Gate Drive — Directly drives power MOSFETs without external buffer
- 500kHz Operation — Enables smaller transformer and filter components
- Built-in UVLO — Prevents operation below safe supply voltage
- Industry Standard — Compatible with UC2842, UC1842, KA3842, NCP3842
Typical Applications
- Flyback SMPS for chargers, adapters, and LED drivers
- Forward converter power supplies
- ATX power supply repair (common UC3842 failure point)
- DC-DC converter modules
- Industrial power supply design
FAQ
Q: What’s the difference between UC3842 and UC3843?
A: UC3843 has a lower UVLO threshold (8.5V start / 7.6V stop) and is better for low-voltage bus applications. UC3842 suits higher-voltage offline supplies.
Q: Can UC3842 SOP-8 replace the DIP-8 version?
A: Electrically yes, but requires SMD PCB footprint. Use a SOP-8 to DIP-8 adapter for through-hole board repair.
Package Contents
- 5× UC3842A/B SOP-8 Current-Mode PWM Controller IC
