Texas Instruments UCC3817AN

Overview

UCC3817AN from Texas Instruments is a BiCMOS average current-mode PFC controller for boost preregulators, delivering near-unity power factor in 250-W IEC61000-3-2-compliant supplies. It features 16-V/10-V UVLO thresholds, ±1.2-A peak gate drive, 7.5-V reference output, and 0.33-V zero-power comparator threshold for light-load efficiency control.

For engineers reviewing the UCC3817AN datasheet, UCC3817AN pinout, UCC3817AN application, or UCC3817AN equivalent, this controller supports world-wide line operation (85–265 VAC), offers leading-edge modulation to reduce bulk capacitor ripple, and integrates accurate voltage/current error amplifiers with 90-dB open-loop gain and <±2-mV offset - critical for low-distortion sinusoidal line current shaping.

Technical Context

The UCC3817AN implements average current-mode control using a high-gain current amplifier (90 dB) and precision voltage amplifier (7.5-V reference, ±2-mV offset) to regulate boost output voltage and shape input current. Its analog multiplier accepts IAC (line-voltage proportional current), VFF (feed-forward RMS voltage), and VAOUT to generate MOUT current for duty-cycle control.

It employs a programmable oscillator (RT/CT pins) with 80–120 kHz total variation, integrated overvoltage protection (1.07% threshold + 500 mV hysteresis), and a robust totem-pole DRVOUT stage with 9-Ω pull-up and 4-Ω pull-down resistance - enabling direct MOSFET gate drive without external buffers in mid-power designs.

Key Specifications

Pinout & Package

UCC3817AN is housed in a 16-pin PDIP (N) package measuring 19.30 mm × 6.35 mm, optimized for through-hole assembly and thermal dissipation in offline PFC stages.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC3817AD and UCC2817AN, the UCC3817AN provides identical PFC control functionality in a through-hole PDIP package with lower thermal resistance - making it ideal for manual assembly, field service, and thermally demanding but temperature-limited commercial power supplies.

Availability

UCC3817AN is available at Aetrix Electronics and suitable for PC power supplies, LED lighting drivers, industrial power modules, and consumer electronics adapters requiring stable component supply and long-term manufacturability.

Supply support for UCC3817AN 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 and embedded processing technologies, with decades of power management innovation.

The UCC3817AN belongs to TI's UCCx81xA BiCMOS PFC controller family, engineered specifically for high-efficiency, low-distortion boost preregulators in sub-300-W IEC61000-3-2-compliant power supplies.

FAQ

What is the UVLO threshold behavior of the UCC3817AN?

The UCC3817AN features an undervoltage lockout with 16-V turn-on and 10-V turn-off thresholds, providing 6-V hysteresis. This ensures clean startup across universal AC inputs and prevents oscillation during brownout conditions. The UVLO circuit is internal and does not require external components. When VCC drops below 10 V, the UCC3817AN disables DRVOUT and discharges the SS capacitor to halt switching - a behavior confirmed in the SLUS577D datasheet Section 8.5.

How does the UCC3817AN implement zero-power detection?

The UCC3817AN monitors VAOUT with an internal comparator set to 0.33 V. When VAOUT falls below this threshold - indicating light-load or no-load conditions - the comparator latches DRVOUT low, halting switching to minimize standby power. This function is independent of OVP/EN and operates continuously. The 0.33-V threshold is specified in Section 9.3.2 of the UCC3817AN datasheet and enables sub-150-mW no-load consumption in properly designed supplies.

Can the UCC3817AN drive a MOSFET directly without external gate drivers?

Yes, the UCC3817AN's DRVOUT pin delivers ±1.2-A peak current with 9-Ω pull-up and 4-Ω pull-down resistance, enabling direct drive of MOSFETs with ≤10-nC total gate charge. A series damping resistor (e.g., 11 Ω) is recommended to suppress ringing. This capability eliminates external drivers in 250-W designs, as verified in the UCC3817AN application schematic (Figure 5, SLUS577D) and Section 9.3.5.4.

What is the role of the MOUT pin in the UCC3817AN control architecture?

MOUT serves as both the analog multiplier output and the inverting input of the current amplifier, forming a high-impedance differential node that enables average current-mode control. It carries the product current IAC × (VAOUT − 1)/VFF², which sets the peak current reference for the PWM latch. This dual role - confirmed in Pin Functions Table 7 and Section 9.3.5.7 - improves noise immunity and allows leading-edge modulation when synchronized with downstream converters.

Does the UCC3817AN support critical conduction mode (CRM) operation?

No - the UCC3817AN is explicitly designed for average current-mode control in continuous conduction mode (CCM) boost topologies. Its block diagram, multiplier architecture, and CAOUT/MOUT feedback path are optimized for CCM operation. CRM operation requires hysteretic or zero-current-sensing control not implemented in the UCC3817AN. For CRM, TI recommends the UCC3805x or UCC3819 families, as noted in Table 2 of the SLUS577D datasheet.