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UC3845 SOP-8 Current-Mode PWM Controller IC 50% Duty Cycle (5-Pack)

$6.04 USD

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UC3845 SOP-8 Current-Mode PWM Controller IC - 50% Max Duty Cycle (5-Pack)

The UC3845 is a current-mode PWM controller in a SOP-8 surface-mount package, identical to the UC3842 but with a 50% maximum duty cycle clamp and lower UVLO thresholds (8.5V on / 7.6V off). The 50% duty cycle limit makes it ideal for forward converters where transformer volt-second balance must be maintained, and the lower UVLO suits lower-voltage auxiliary supply designs.

Key Specifications

Parameter	Value
Part Number	UC3845
Package	SOP-8 (SMD)
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

UC384x Family - Choose the Right Part

Part	Max Duty Cycle	UVLO On/Off	Package
UC3842	100%	16V / 10V	DIP-8 / SOP-8
UC3843	50%	8.5V / 7.6V	DIP-8 / SOP-8
UC3844	50%	16V / 10V	DIP-8 / SOP-8
UC3845	50%	8.5V / 7.6V	DIP-8 / SOP-8

Why Choose UC3845?

50% Duty Cycle Clamp - Prevents transformer saturation in forward converter designs
Low UVLO (8.5V/7.6V) - Starts up from lower auxiliary supply voltages vs UC3842/3844
Current-Mode Control - Inherent cycle-by-cycle OCP and improved transient response
SOP-8 SMD Package - Compact footprint for modern SMPS PCB designs
Drop-in for UC3843 - Same pinout and function as UC3843 (SOP-8 version)

Typical Applications

Single-ended forward converter SMPS
DC-DC converter with 50% duty cycle limit
Flyback converter (lower UVLO for auxiliary startup)
SMPS repair replacement for UC3843/UC3845
Industrial power supply controller

FAQ

Q: Can UC3845 replace UC3843? Yes - UC3845 and UC3843 are electrically identical (same pinout, same UVLO, same 50% duty cycle). UC3845 is the SOP-8 SMD version; UC3843 is typically DIP-8.

Q: Why use UC3845 instead of UC3842 for a forward converter? Forward converters require duty cycle below 50% to prevent transformer core saturation. UC3845 enforces this limit in hardware, preventing accidental saturation if the feedback loop fails.