Texas Instruments UC2853N

Overview

UC2853N from Texas Instruments is an 8-pin active power factor correction (PFC) controller IC designed for average current mode control in AC-DC preregulators. It integrates a precision multiplier/squarer/divider, dual error amplifiers (voltage and current loops), internal 75 kHz oscillator with synchronization capability, RMS line voltage compensation, and a clamped high-current gate driver. It operates across –25°C to +85°C and targets universal-input (85–265 VAC) offline power supplies.

For engineers reviewing the UC2853N datasheet, UC2853N pinout, UC2853N application, or UC2853N equivalent, key selection considerations include its RMS-compensated average current mode architecture, 75 kHz synchronizable oscillator, –25°C to +85°C temperature rating, SOIC-8/PDIP-8 package options, and compatibility with high-voltage MOSFET gate driving in boost PFC stages.

Technical Context

The UC2853N implements average current mode PWM control using a transconductance voltage amplifier (VCOMP) and a differential current amplifier (ICOMP), with the multiplier output (IMO) serving as both squarer/divider output and current-sense inverting input. Its internal oscillator provides 75 kHz nominal frequency (56–94 kHz over line/load/temperature) and accepts external sync pulses via FB pin with 2 V falling-edge trigger.

RMS line voltage compensation is achieved by routing a DC voltage proportional to input RMS voltage to VCC, scaling the voltage loop gain by 1/√V_CC. The device features undervoltage lockout (13 V turn-on, 1.8 V hysteresis), overvoltage protection (90–150 mV threshold above EA input), and a self-biasing gate driver that clamps OUT to ≤17.5 V while sinking up to 50 mA.

Key Specifications

Pinout & Package

UC2853N is supplied in an 8-pin plastic dual in-line package (PDIP-8, package code P), with lead finish NIPDAU and no MSL rating applicable. Pin spacing is 0.1 inch (2.54 mm), body width 0.300 inch (7.62 mm), and total length 0.375 inch (9.53 mm).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar active power factor correction controller applications.

Compared with UC3853N and L6562A, the UC2853N uniquely delivers –25°C to +85°C operation with integrated RMS compensation and oscillator sync-enabling single-chip universal-input PFC without external feedforward circuitry or thermal derating.

Availability

UC2853N is available at Aetrix Electronics and suitable for server power supplies, industrial AC-DC converters, medical power modules, and outdoor LED drivers requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for UC2853N includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and power management applications.

The UC2853N belongs to TI's legacy UCx853 family of active PFC controllers, engineered specifically for cost-effective, high-efficiency boost preregulators in universal-input offline power supplies.

FAQ

What is the operating temperature range specified for the UC2853N?

The UC2853N is rated for operation from –25°C to +85°C ambient temperature. This specification is confirmed in the Absolute Maximum Ratings table and Electrical Characteristics section of the official datasheet, distinguishing it from the UC1853 (–55°C to +125°C) and UC3853 (0°C to +70°C). The UC2853N's temperature grade makes it suitable for commercial and industrial power supplies where extended cold-start capability is required but full military-grade range is not necessary. Designers should verify thermal design margins under worst-case load and airflow conditions to ensure junction temperature remains within –55°C to +150°C limits.

Does the UC2853N support synchronization with external clock signals?

Yes, the UC2853N supports synchronization via its FB pin, which doubles as a sync input. A 2 V falling-edge clock pulse with ≥100 V/µs slew rate can be injected through a capacitor to align the internal 75 kHz oscillator with downstream converters. This feature is explicitly documented in the PIN DESCRIPTIONS section and Electrical Characteristics table under "Synchronization Pulse Amplitude" and "Synchronization Frequency Range." Proper implementation requires slow-rising/fast-falling edges to avoid false triggering of the overvoltage comparator also tied to FB. The UC2853N's sync capability helps suppress beat frequencies and simplify EMI filter design in multi-stage power architectures.

What is the purpose of the VCC pin beyond supplying power to the UC2853N?

Beyond powering the UC2853N, the VCC pin serves as the RMS line voltage sensing input for automatic loop gain scaling. When a DC voltage proportional to the rectified input's RMS value is applied to VCC, the internal squarer circuit divides the voltage loop gain by √V_CC, maintaining constant gain across 85–265 VAC input. This function is detailed in the DESCRIPTION and PIN DESCRIPTIONS sections, and is fundamental to achieving low THD without external RMS-to-DC converters. The UC2853N's VCC range (12–40 V) supports direct connection to a scaled version of the bulk DC bus or a dedicated RMS-sensing network, enabling true universal-input operation with minimal external components.

How does the UC2853N implement overvoltage protection?

The UC2853N implements overvoltage protection (OVP) using a dedicated comparator that monitors the FB pin voltage relative to the voltage amplifier's inverting input. If FB rises above nominal regulation (3 V) by 90–150 mV-i.e., to 3.09–3.15 V-the comparator triggers immediate shutdown of the OUT driver until the output decays by ≥80 mV hysteresis. This behavior is specified in the Electrical Characteristics table under "OVP Comparator Section" and described in the FB pin definition. No external components are required, and the OVP threshold is internally trimmed, providing fast, reliable protection for the downstream DC-DC stage and bulk capacitor without adding delay or complexity.

Can the UC2853N drive a MOSFET directly without external gate-driving components?

Yes, the UC2853N integrates a high-current, clamped gate driver on its OUT pin capable of sinking 50 mA and sourcing sufficient current to charge typical MOSFET gates. Its 15 V internal clamp prevents gate-source overvoltage even when VCC reaches 40 V maximum, eliminating the need for external Zener diodes in most designs. However, a series gate resistor (≥5 Ω) is recommended to dampen ringing and limit clamp overshoot, and a Schottky diode (e.g., 1N5818) from OUT to GND may be needed to block parasitic substrate conduction. These recommendations appear in the PIN DESCRIPTIONS section and are validated in the UC3853 Typical Application schematic.