Texas Instruments UCC3817AD

Overview

UCC3817AD from Texas Instruments is a BiCMOS average current-mode power factor correction (PFC) controller for boost preregulators, featuring 16-V/10-V UVLO thresholds, 7.5-V reference output, ±1.2-A peak gate drive, and 6–220-kHz programmable oscillator frequency. It enables near-unity power factor in <300-W IEC61000-3-2-compliant AC/DC supplies for PC power and lighting applications.

For engineers reviewing the UCC3817AD datasheet, UCC3817AD pinout, UCC3817AD application, or UCC3817AD equivalent, key selection considerations include its average current mode control architecture, shunt-regulated VREF output, OVP/EN dual-function pin, soft-start current source, and compatibility with SOIC-16 packaging for industrial and consumer power supply designs.

Technical Context

The UCC3817AD implements average current mode control using a high-gain current amplifier (90 dB open-loop gain, ±2 mV offset), multiplier-based feed-forward line regulation (VFF input, K = 1/V gain constant), and leading-edge PWM modulation synchronized to reduce bulk capacitor ripple. Its zero-power comparator latches DRVOUT low when VAOUT falls below 0.33 V.

It integrates a 7.5-V precision voltage reference (±1.5% accuracy, 10-mV load/line regulation), UVLO with 6.3-V hysteresis (16-V turn-on / 9.7-V turn-off), and a totem-pole gate driver with 9-Ω pull-up / 4-Ω pull-down resistance-enabling robust MOSFET switching at up to 99% duty cycle.

Key Specifications

Pinout & Package

UCC3817AD is housed in a 16-pin SOIC (D package), 4.90 mm × 3.91 mm body size, with standard JEDEC MS-012AC footprint and gull-wing leads.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC2817AD and UC3854BDW, the UCC3817AD offers the best balance of integration (on-chip 7.5-V VREF, OVP/EN, soft-start), commercial temperature suitability, and average current mode stability for sub-300-W IEC61000-3-2 applications-reducing BOM count and layout complexity without sacrificing performance.

Availability

UCC3817AD 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 manufacturability.

Supply support for UCC3817AD 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 delivering analog and embedded processing solutions, with leadership in power management ICs and industrial-grade reliability.

The UCC3817AD belongs to TI's UCCx81xA BiCMOS PFC controller family, designed specifically for cost-effective, high-efficiency active power factor correction in sub-300-W universal-input AC/DC power supplies.

FAQ

What is the operating temperature range for the UCC3817AD?

The UCC3817AD is specified for operation from 0°C to 70°C ambient temperature. This commercial-grade rating distinguishes it from the extended-temperature UCC2817AD (–40°C to 85°C). The device's BiCMOS process ensures stable performance across this range, with electrical characteristics guaranteed per the SLUS577D datasheet under these conditions. Thermal derating is not required within this envelope.

How does the UCC3817AD implement overvoltage protection?

The UCC3817AD uses its OVP/EN pin as a window comparator: switching halts when the voltage exceeds 1.07×VREF + 500 mV hysteresis (≈8.0 V typical), and soft-start is reset if the pin drops below 1.9 V. This dual-function design allows coordinated protection of the boost output and controlled startup sequencing. The internal reference ensures accuracy independent of external resistor tolerances.

Can the UCC3817AD be used in critical conduction mode (CRM)?

No-the UCC3817AD is explicitly an average current-mode controller optimized for continuous conduction mode (CCM) boost topologies. Its architecture-including the current amplifier, multiplier, and PWM latch-requires sensed average current feedback and fixed-frequency operation. CRM applications require hysteretic or variable-frequency controllers like the UCC38051 or UCC3819, which are not functionally compatible with the UCC3817AD.

What is the purpose of the VFF pin on the UCC3817AD?

The VFF (voltage feed-forward) pin accepts a scaled RMS representation of the AC input voltage (1.4 V at low line, 4.7 V at high line) to dynamically adjust the multiplier gain. This compensates for line-voltage variations, maintaining consistent power limiting and improving line regulation-critical for universal-input operation. The VFF signal is generated externally using a resistor divider and RC filter from the rectified AC line.

Does the UCC3817AD include an internal voltage reference?

Yes-the UCC3817AD integrates a precision 7.5-V shunt voltage reference (VREF pin) with ±1.5% initial accuracy, 10-mV load and line regulation, and 20-mA output capability. It powers external circuitry (e.g., PKLMT divider) and is disabled below UVLO threshold. This eliminates the need for an external reference in most PFC designs, reducing component count and cost.