Texas Instruments UCC3818AN

Overview

UCC3818AN from Texas Instruments is a BiCMOS average current-mode power factor correction (PFC) controller for boost preregulators, featuring 10.2 V/9.7 V UVLO turn-on/turn-off thresholds, 7.5 V reference output, ±1.2 A peak gate drive, and 6–220 kHz programmable oscillator frequency. It enables IEC 61000-3-2-compliant <300 W AC-DC supplies in PC power, lighting, and industrial systems.

For engineers reviewing the UCC3818AN datasheet, UCC3818AN pinout, UCC3818AN application, or UCC3818AN equivalent, key selection criteria include its fixed-supply VCC operation (vs bootstrap-capable UCC3817A), 0.33 V zero-power comparator threshold, 1.9 V enable threshold on OVP/EN, and average-current-mode control architecture optimized for low-line distortion and feed-forward line regulation.

Technical Context

The UCC3818AN implements average current-mode control using a high-gain current amplifier (90 dB open-loop gain, ±2 mV offset) and a three-input analog multiplier (IAC, VAOUT, VFF) to generate duty cycle commands synchronized to line voltage. Its leading-edge PWM modulation reduces bulk capacitor ripple current when coordinated with downstream DC-DC stages.

It integrates a 7.5 V precision reference (±1.5% over temperature), UVLO with 0.5 V hysteresis, overvoltage protection with 500 mV hysteresis at OVP/EN, and soft-start via internal 10 µA current source charging an external capacitor. The gate driver delivers ±1.2 A peak into capacitive loads with 9 Ω pull-up and 4 Ω pull-down resistance.

Key Specifications

Pinout & Package

UCC3818AN is packaged in a 16-pin PDIP (N package) with body size 19.30 mm × 6.35 mm, suitable for through-hole assembly and thermal relief via PCB copper pour.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PFC controller applications.

Compared with UCC3817AN and UC3854BDW, the UCC3818AN offers optimal integration for fixed-supply 100–300 W PFC stages-delivering lower BOM count, reduced layout complexity, and guaranteed IEC 61000-3-2 compliance without external compensation.

Availability

UCC3818AN is available at Aetrix Electronics and suitable for PC power supplies, LED lighting drivers, industrial AC-DC adapters, and consumer audio power supplies requiring stable component supply and long-term production continuity.

Supply support for UCC3818AN 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 personal electronics markets.

The UCC3818AN belongs to TI's UCCx81xA BiCMOS PFC controller family, engineered specifically for high-efficiency, low-distortion active power factor correction in sub-300 W universal-input AC-DC power supplies.

FAQ

What is the UVLO threshold for UCC3818AN?

The UCC3818AN features a 10.2 V turn-on threshold and 9.7 V turn-off threshold on the VCC pin, providing 0.5 V hysteresis to prevent oscillation during brownout conditions. This fixed-threshold UVLO is distinct from the 16 V/10 V UVLO of the UCC3817A variant and confirms the UCC3818AN's design for fixed-supply operation rather than bootstrap configurations. The UCC3818AN remains disabled until VCC exceeds 10.2 V, ensuring reliable startup only when sufficient gate drive voltage is available.

How does UCC3818AN implement average current-mode control?

The UCC3818AN uses a dedicated current amplifier with CAI (noninverting) and MOUT (inverting) inputs to measure and regulate inductor current in real time. Its analog multiplier combines IAC (line voltage current), VAOUT (voltage error), and VFF (feed-forward voltage) to generate a reference for the current loop. This architecture maintains near-sinusoidal input current with <2 mV amplifier offset, directly enabling IEC 61000-3-2 Class D compliance. The UCC3818AN does not use peak-current-mode or voltage-mode control.

What is the function of the OVP/EN pin on UCC3818AN?

The OVP/EN pin on the UCC3818AN serves a dual function: it acts as a window comparator for overvoltage protection (triggering shutdown when boost output exceeds the programmed threshold) and as an enable input (disabling the controller when pulled below 1.9 V). Unlike the UCC3817A, the UCC3818AN does not integrate a shunt regulator on this pin. The 500 mV hysteresis prevents chatter during transient overvoltage events, and the 1.9 V enable threshold allows clean system-level sequencing with microcontrollers or supervisor ICs.

Can UCC3818AN be used with a bootstrap VCC supply?

No - the UCC3818AN is explicitly designed for fixed-rail VCC operation and lacks the internal shunt regulator required for bootstrap supply configurations. Attempting to use it with a bootstrap supply risks failure to start or unstable operation due to insufficient VCC regulation. For bootstrap applications, the UCC3817A variant must be selected instead. The UCC3818AN requires a stable 12–18 V supply capable of delivering ≥20 mA, bypassed directly to GND with ≥0.1 µF ceramic capacitance.

What oscillator components set the switching frequency of UCC3818AN?

The UCC3818AN switching frequency is set by an external resistor (RT) from pin 12 to GND and an external capacitor (CT) from pin 14 to GND, following the formula f ≈ 0.6/(RT × CT). With typical values of RT = 22 kΩ and CT = 270 pF, the nominal frequency is 100 kHz. The oscillator supports a full range of 6–220 kHz, allowing designers to optimize for EMI, magnetics size, and efficiency. The CT trace must be short and direct to GND to minimize noise coupling into the timing circuit.