Texas Instruments UCC3818D

Overview

UCC3818D from Texas Instruments is a BiCMOS active power factor correction (PFC) controller for boost preregulators, implementing average current-mode control to achieve near-unity power factor and low line current distortion. It features a 7.5-V precision reference, 10.5 V/10 V UVLO threshold, leading-edge PWM modulation, and integrated gate driver with 0.2-A continuous output. Used in IEC 61000-3-2-compliant sub-300 W AC/DC supplies for PC and industrial power systems.

For engineers reviewing the UCC3818D datasheet, UCC3818D pinout, UCC3818D application, or UCC3818D equivalent, key selection considerations include its 10.5 V turn-on UVLO, 7.5-V reference accuracy (±1.5%), soft-start current (−10 µA typical), peak current limit interface (PKLMT), and compatibility with 6–220 kHz oscillator range via RT/CT programming.

Technical Context

The UCC3818D integrates an analog multiplier with three inputs-VAOUT (voltage error signal), IAC (line voltage proportional current), and VFF (feed-forward RMS voltage)-to generate a precise current command for the PFC stage. Its average current-mode architecture uses CAI/MOUT differential sensing and CAOUT-driven PWM latch to maintain stable sinusoidal input current even under wide line and load variations.

It employs a dedicated zero-power comparator (threshold: 0.33 V on VAOUT) to disable switching during light-load or no-load conditions, reducing standby losses. The internal 7.5-V reference powers external circuitry (up to 20 mA), while OVP/EN provides windowed overvoltage protection and enable control with 1.9 V lower threshold and 500 mV hysteresis.

Key Specifications

Pinout & Package

UCC3818D is housed in a 16-pin SOIC (D) package measuring 3.91 mm × 9.9 mm, with standard JEDEC MS-012AC footprint and 1.27 mm pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC2818D and UCC3817D, the UCC3818D provides optimal balance of commercial-temperature operation, low-UVLO startup, and proven IEC61000-3-2 compliance for sub-300 W universal-input supplies-making it the default choice unless extended temp or high-VCC requirements apply.

Availability

UCC3818D is available at Aetrix Electronics and suitable for PC power supplies, industrial AC/DC adapters, LED driver front-ends, and consumer electronics power stages requiring stable component supply and long-lifecycle support.

Supply support for UCC3818D 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 specializing in analog, embedded processing, and power management technologies, with decades of expertise in power conversion IC design.

The UCC3818D belongs to TI's BiCMOS PFC controller product line, engineered specifically for cost-sensitive, high-efficiency active power factor correction in universal-input AC/DC power supplies under 300 W.

FAQ

What is the UVLO threshold for UCC3818D?

The UCC3818D features an undervoltage lockout with a turn-on threshold of 10.5 V and turn-off threshold of 9.7 V, providing 0.5 V hysteresis to prevent oscillation during brownout conditions. This ensures reliable startup from 10 V–17 V VCC supply while avoiding false triggering near the lower operating limit. The UCC3818D's UVLO is distinct from the 16 V/9.7 V of UCC3817D and the 10.2 V/9.7 V of UCC2818D.

Does UCC3818D support leading-edge or trailing-edge PWM modulation?

The UCC3818D implements leading-edge PWM modulation, which synchronizes the switch turn-on edge with the oscillator clock to reduce ripple current in the bulk output capacitor. This feature lowers RMS current stress and extends capacitor lifetime-especially beneficial in compact, thermally constrained designs like slim TVs or enclosed LED drivers. Trailing-edge modulation is not supported.

Can UCC3818D be used in place of UCC2818D?

The UCC3818D and UCC2818D share identical pinout, functional architecture, and electrical specifications except for temperature rating: UCC3818D operates from 0°C to +70°C, while UCC2818D supports −40°C to +85°C. Substituting UCC3818D in a design qualified for extended temperature may result in failure outside its specified range; always verify ambient and junction temperatures before replacement.

What is the purpose of the VFF pin on UCC3818D?

The VFF (feed-forward voltage) pin on UCC3818D accepts an RMS-representative voltage derived from the AC line-typically 1.4 V at low line and ~4.7 V at high line-to scale the multiplier gain dynamically. This improves line regulation and reduces total harmonic distortion across universal input (85–265 VAC), enabling consistent power factor >0.98 without manual tuning across voltage ranges.

How does the zero-power detection function work in UCC3818D?

The UCC3818D includes a zero-power comparator that monitors VAOUT and triggers when voltage falls below 0.33 V-indicating near-zero output load. Upon detection, it latches the gate driver low, halting switching to minimize standby power consumption. This feature is essential for meeting Energy Star and EU CoC Tier 2 efficiency requirements in no-load and light-load conditions.