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UC2845N

Name: UC2845N
Rating: 4.7 (12 reviews)

IC REG CTRLR BOOST/FLYBACK 8DIP

製造商
製造商。部分 #UC2845N
包 8-DIP (0.300, 7.62mm)
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規格

Supplier	onsemi
Package	Tube
ProductStatus	Obsolete
OutputType	Transistor Driver
Function	Step-Up, Step-Up/Step-Down
OutputConfiguration	Positive, Isolation Capable
Topology	Boost, Flyback
NumberofOutputs	1
OutputPhases	1
Voltage-Supply(Vcc/Vdd)	7.6V ~ 30V
Frequency-Switching	Up to 500kHz
DutyCycle(Max)	48%
SynchronousRectifier	No
ClockSync	No
ControlFeatures	Frequency Control
OperatingTemperature	-25°C ~ 85°C (TA)
MountingType	Through Hole
Package/Case	8-DIP (0.300, 7.62mm)

概述

Description

The UC2845N is a fixed‑frequency, current‑mode PWM controller from TI/Unitrode (UC28xx family). It provides a complete switch‑mode power supply control loop with:
- Built‑in 5V reference, undervoltage lockout, cycle‑by‑cycle current limiting, and soft‑start
- An external RT resistor to set oscillator frequency (typical tens of kHz)
- A current‑sense input that monitors the primary switch current and a feedback path (often via an optocoupler) to regulate output voltage by adjusting duty cycle
- Capability to drive a power MOSFET directly, suitable for various topologies
Common applications include flyback, buck, boost, and forward converters in offline and DC‑DC SMPS, such as power adapters, telecom supplies, and LED drivers.
Packaging is DIP‑8 or SO‑8 (N suffix indicates the package type). For exact electrical specs and pinout, consult the UC2845N datasheet.

Features

UC2845N is a current‑mode PWM controller for switch‑mode power supplies. Key features include:
- 5V reference and error amplifier for feedback (via optocoupler)
- External timing components to set switching frequency (RT/CT)
- High‑voltage startup and low quiescent supply current
- Pulse‑width modulated, current‑mode control with peak current limiting (cycle‑by‑cycle protection)
- Leading‑edge blanking on current sense input
- Undervoltage lockout with hysteresis
- Overcurrent/short‑circuit protection with latch
- Thermal/shutdown protection
- Output stage capable of driving the main switch (compatible with flyback/forward topologies)
- Available in 8‑pin DIP package (N)
These make it suitable for offline and DC‑DC SMPS applications using standard feedback via optocoupler.

Package

UC2845N comes in an 8-pin DIP (N) package — a plastic through-hole dual-in-line package.

Pinout

UC2845N is an 8-pin device (DIP-8/SO-8). It is a current‑mode PWM controller for switch‑mode power supplies. It provides regulated duty cycle by comparing a feedback signal (via FB/Vref) to an internal reference, uses a current‑sense input (IS) for peak current control, and drives the switching transistor through the OUTPUT pin. It includes an oscillator (RT/CT) for frequency setting, a COMP pin for loop compensation, an internal 5V reference (Vref), and protection/UVLO features. Pins typically: Vcc, Gnd, Output, IS (current sense), FB/Vref, COMP, RT/CT, and Vref.

Manufacturer

- Manufacturer: Unitrode Corporation (tradename Unitrode; now part of Texas Instruments).
- What kind of company: A semiconductor company specializing in analog and mixed-signal integrated circuits, especially power-management ICs and switching-power controllers; Unitrode was later acquired by Texas Instruments.

Application

UC2845N is a current‑mode PWM controller for off‑line SMPS. Typical applications:
- Flyback and forward isolated power supplies
- AC‑DC adapters and wall‑wart power supplies
- Power rails for TVs/monitors/set‑top boxes
- LED constant‑current drivers
- Small telecom/industrial power supplies

Equivalent

Likely equivalents (pin‑compatible current‑mode PWM controllers) include:
- UC3842/UC3843/UC3844/UC3845 (TI/Unitrode family)
- KA3842/KA3843/KA3844/KA3845 (Korea/other manufacturers)
Notes: UC2845N is essentially part of the UC384x family; minor pinout/UVLO differences can exist. Always verify datasheets for exact pin compatibility and electrical specs before substituting.