UC2845N

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UC2845N

+Nomenclature

IC REG CTRLR BOOST/FLYBACK 8DIP

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Spécifications

Attribut Valeur
Supplier onsemi
Package / Case Tube
Part Status Obsolete
Output Type Transistor Driver
Function Step-Up, Step-Up/Step-Down
Output Configuration Positive, Isolation Capable
Topology Boost, Flyback
Number of Outputs 1
Output Phases 1
Voltage - Supply (Vcc/Vdd) 7.6V ~ 30V
Frequency - Switching Up to 500kHz
Duty Cycle(Max) 48%
Synchronous Rectifier No
Clock Sync No
Control Features Frequency Control
Operating Temperature -25°C ~ 85°C (TA)
Mounting Type Through Hole

Présentation

Description

The UC2845N is a current‑mode PWM controller IC from Unitrode/TI used in switch‑mode power supplies. It integrates a 5V reference, error amplifier, oscillator, current-sense input, PWM comparator, soft‑start, undervoltage lockout, and latchable overcurrent protection. It drives a power switch (MOSFET/BJT) in flyback/forward converters, using feedback from the secondary via an optocoupler.
Key points
- Pinout: 8-pin DIP/SOIC (N suffix indicates DIP/SOIC package)
- Supply and operation: Vcc typically 8–40 V
- Frequency: oscillator set by external resistor (tens to hundreds of kHz)
- Feedback: 5V reference for error amp and opto isolation for regulation
- Protections: soft‑start, current limit, fault latch/UVLO
- Applications: offline and DC‑DC SMPS (telecom, computer, consumer power supplies)
In short, it’s a classic, cost‑effective PWM controller for high‑volume power supplies.

Equivalent

Equivalent parts to UC2845N (current-mode PWM controller) include:
- UC3842/3843/3844/3845 family (TI/Unitrode)
- KA3842/KA3843/KA3844/KA3845 family (Samsung/KA)
Many catalogs list these as cross-references to UC2845N. Always verify exact electrical specs (start-up current, reference, slope compensation) for your design.

Pinout

- Pin count: 16 pins (DIP/N package).
- Function: A high-voltage, current‑mode PWM controller for switch‑mode power supplies. It contains a high‑voltage startup source, a 5V reference, error amplifier with compensation, voltage feedback and current sensing inputs, an oscillator (timing via RT/CT), and a gate‑drive output for the power switch, plus protection (e.g., undervoltage).

Manufacturer

- Manufacturer: Texas Instruments (TI), leveraging the Unitrode lineage. Unitrode Corporation originally designed the UC2845N; it was acquired by TI in the 1990s, and TI now markets it.
- What kind of company: TI is an American multinational semiconductor company; Unitrode was a U.S. semiconductor outfit specializing in analog and power-management ICs.

Application

UC2845N is a high‑voltage, current‑mode PWM controller for switch‑mode power supplies. Typical applications include:
- Offline AC‑DC SMPS (flyback/forward converters)
- Isolated and non‑isolated DC‑DC front ends for telecom and consumer electronics
- Battery chargers
- LED constant‑current drivers
- Compact power supplies for printers, set‑top boxes, and similar devices

Package

UC2845N comes in an 8-pin DIP (through-hole) package; the N suffix indicates the DIP packaging.

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