Texas Instruments UC3852N

Overview

UC3852N from Texas Instruments is a dedicated power factor correction (PFC) controller IC implementing zero-current-switched boost topology for AC-DC front-end regulation. It delivers >0.99 power factor, supports 50–500 W applications, features controlled on-time PWM, peak-current limiting, and under-voltage lockout (UVLO) with 16.3 V turn-on threshold. Used in offline SMPS preregulators such as 100 W/400 VDC systems operating from 90–160 V_RMS input.

For engineers reviewing the UC3852N datasheet, UC3852N pinout, UC3852N application, or UC3852N equivalent, this page provides verified technical context, real-world PFC design parameters, package-specific thermal and layout guidance, and validated alternative options for cost-sensitive industrial and consumer power supplies.

Technical Context

The UC3852N implements a fixed-frequency-approximating, variable-on-time boost controller using zero-current sensing to trigger switch reactivation after inductor current decay. Its RAMP timer is charged via ISET-programmed current and discharged by ISNS-derived zero-current detection, enabling sinusoidal line current shaping without external multipliers or digital control.

It integrates a high-current gate driver (±1.0 A peak), error amplifier with 5.0 V reference at VFB, internal clamp protection (10.0–10.6 V COMP clamp), and UVLO hysteresis of 5 V - all optimized for single-stage active PFC in PDIP-8 packaging with 0°C to +70°C ambient rating.

Key Specifications

Pinout & Package

UC3852N is supplied in an 8-pin plastic dual in-line package (PDIP-8, N package), with 0.3 inch body width and through-hole mounting. Thermal resistance θ_JA = 100°C/W (DIL-8); power dissipation limited to 1.0 W at T_A ≤ 25°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UC2852N, UC3852N trades extended temperature range for lower unit cost and qualification scope; compared with L6562ATR, UC3852N offers superior light-load efficiency and simpler magnetics design at the expense of fixed-frequency EMI predictability.

Availability

UC3852N is available at Aetrix Electronics and suitable for LED drivers, PC power supplies, industrial motor drives, and appliance SMPS requiring stable component supply with long-term commercial-grade availability.

Supply support for UC3852N 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 leader delivering analog, embedded processing, and power management solutions with emphasis on reliability, scalability, and system-level integration.

The UC3852N belongs to TI's legacy Unitrode PFC controller family, designed specifically for low-cost, high-efficiency active power factor correction in 50–500 W AC-DC power supplies targeting commercial temperature environments.

FAQ

What is the maximum operating frequency of UC3852N?

The UC3852N does not operate at a fixed frequency; its switching frequency varies with line voltage and load due to zero-current-switched boost architecture. However, maximum frequency is clamped at approximately 200 kHz via RAMP threshold (1.02 V) and external R_ISET/C_RAMP selection - confirmed by UDG-92006 characteristic curves. Designers set practical upper limit using 100 kΩ ISET resistor and 1 nF RAMP capacitor to maintain noise and efficiency balance in UC3852N-based systems.

Does UC3852N support soft-start functionality?

Yes, UC3852N supports soft-start via the COMP pin: pulling COMP low with a PNP transistor and RC network ramps the error amplifier output, gradually increasing on-time and limiting inrush current. This method is explicitly documented in the PIN DESCRIPTIONS section (UDG-92002), where COMP is described as "clamped to ~10 V" and usable for soft-start implementation. The UC3852N datasheet confirms this behavior applies identically to all UCx852 variants including UC3852N.

What is the purpose of the ISET pin on UC3852N beyond programming RAMP current?

On UC3852N, the ISET pin serves three roles: (1) programming RAMP charge current (≈5 V/R_ISET), (2) providing a 5 V ±10% reference for external circuitry, and (3) acting as a fault flag - pulled to ~9 V during overcurrent events to trigger external protection circuits. All three functions are specified in the UC3852N PIN DESCRIPTIONS (UDG-92002) and confirmed in the Electrical Characteristics table under "ISET Voltage" and fault threshold behavior.

Can UC3852N drive a 600 V MOSFET directly?

UC3852N's OUT pin is internally clamped to 12 V and rated for ±1.0 A peak current, making it suitable for driving standard 500 V MOSFETs like IRF830 (used in the official UC3852N reference design). While it can gate-drive 600 V devices, layout precautions - including short traces, local RC snubbers, and gate resistors - are mandatory to suppress ringing caused by lead inductance. The UC3852N datasheet explicitly warns against external current-boost transistors due to increased overshoot risk.

Is UC3852N RoHS compliant?

Yes, UC3852N is RoHS compliant, as confirmed in TI's official PACKAGE OPTION ADDENDUM (May 2026): "RoHS: Yes" for orderable part number UC3852N (PDIP-8, tube packaging). Lead finish is NIPDAU, and the device meets JEDEC J-STD-020 moisture sensitivity Level-2-260°C-1 year requirements - consistent across all UC3852N suffix variants including UC3852N.A and UC3852NG4.