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UC3842 SOP-8 Current-Mode PWM Controller IC UC3842A UC3842B (5-Pack)

$6.28 USD

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UC3842 SOP-8 Current-Mode PWM Controller IC (5-Pack)

The UC3842 is a high-performance fixed-frequency current-mode PWM controller in a SOP-8 surface-mount package. Operating up to 500kHz with a 1A totem-pole gate drive output, it is the industry-standard controller for flyback, forward, and boost SMPS designs. The UC3842A and UC3842B variants differ only in UVLO thresholds.

Key Specifications

Parameter	Value
Part Number	UC3842 / UC3842A / UC3842B
Package	SOP-8 (SMD)
Topology	Current-mode PWM (fixed frequency)
Max Oscillator Frequency	500kHz
Gate Drive Output	1A peak (totem-pole)
Duty Cycle	0 - 100% (UC3842) / 0 - 50% (UC3843)
UVLO Thresholds	16V on / 10V off (UC3842A: 16V/10V, UC3842B: 16V/10V)
Reference Voltage	5V (2% accuracy)
Current Sense Input	1V threshold (cycle-by-cycle OCP)
Operating Temperature	0C to +70C (UC3842) / -40C to +85C (UC3842A)
Quantity	5 pieces

UC384x Family Comparison

Part	Max Duty Cycle	UVLO On/Off	Temp Range
UC3842	100%	16V / 10V	0 to +70C
UC3843	50%	8.5V / 7.6V	0 to +70C
UC3844	50%	16V / 10V	0 to +70C
UC3845	50%	8.5V / 7.6V	0 to +70C

Why Choose UC3842?

Current-Mode Control - Inherent cycle-by-cycle overcurrent protection and improved line regulation
500kHz Operation - Enables small transformer and filter components
1A Gate Drive - Directly drives power MOSFETs up to ~10nC gate charge without external buffer
5V Reference - Accurate 2% reference for feedback network design
Industry Standard - Extensive application notes and reference designs available

Typical Applications

Flyback SMPS (offline, isolated)
Forward converter power supply
Boost PFC pre-regulator
DC-DC converter controller
SMPS repair replacement (common in monitors, TVs, adapters)

FAQ

Q: What is the difference between UC3842 and UC3843? UC3842 allows 0-100% duty cycle; UC3843 is limited to 0-50% (built-in duty cycle clamp). UC3843 is preferred for forward converters to prevent transformer saturation.

Q: What MOSFET can UC3842 drive directly? MOSFETs with Qg up to ~10nC at the target switching frequency. For larger MOSFETs, add a totem-pole gate driver (TC4427, UCC27321) between UC3842 output and gate.