Texas Instruments UCC28501DWTR

Overview

UCC28501DWTR from Texas Instruments is a dual-stage active power factor correction (PFC) and DC-DC controller IC integrating average-current-mode PFC control with peak-current-mode downstream PWM control in a single 20-pin SOIC package. It delivers near-unity power factor, programmable 80–120 kHz oscillator frequency, 7.5 V reference accuracy (±15 mV), and synchronized leading-edge (PFC) / trailing-edge (DC-DC) modulation for reduced bulk-capacitor ripple in universal-input AC-DC power supplies.

For engineers reviewing the UCC28501DWTR datasheet, UCC28501DWTR pinout, UCC28501DWTR application, or UCC28501DWTR equivalent, key selection criteria include its narrow UVLO threshold (10.5 V turn-on / 10 V turn-off) optimized for fixed-bias operation, dual-gate drivers (GT1/GT2) with 5–12 Ω pull-up/pull-down resistance, and integrated feedforward line regulation via VFF pin for stable input power across 85–265 V_RMS inputs.

Technical Context

The UCC28501DWTR implements a two-stage control architecture: the PFC section uses average current-mode control with a high-linearity analog multiplier (K = 0.5–1.5 V⁻¹), low-offset current amplifier (±6 mV), and zero-power detection (0.175–0.5 V VAOUT threshold); the DC-DC stage employs peak-current-mode control with external error feedback via VERR, 50% maximum duty cycle clamp, and programmable soft-start via SS2 charge current (−7.3 to −12.5 µA).

Line feedforward is generated by mirroring IAC current into an external RC filter at the VFF pin, producing a voltage proportional to RMS line voltage-enabling constant input power regulation without high-voltage sensing components. The device supports synchronized start-up: the second stage remains disabled until PFC output reaches regulation (within 10%), then executes controlled soft-start to limit inrush stress.

Key Specifications

Pinout & Package

UCC28501DWTR is housed in a 20-pin SOIC (DW) package with 0.65 mm pitch, rated for –40°C to +85°C operating temperature and compatible with standard surface-mount reflow profiles.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-stage PFC+PWM controller applications.

Compared with UCC28502DWTR and UCC28070DR, the UCC28501DWTR uniquely combines fixed-bias UVLO compatibility, integrated dual-stage control, and synchronized modulation-reducing component count and simplifying timing coordination in compact universal-input power supplies.

Availability

UCC28501DWTR is available at Aetrix Electronics and suitable for industrial AC-DC power supplies, medical equipment power modules, and telecom rectifier units requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for UCC28501DWTR 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 over 50 years of innovation in power conversion ICs.

The UCC2850x product line was engineered specifically for cost-sensitive, high-reliability two-stage AC-DC power supplies requiring integrated PFC and isolated DC-DC control in a single package.

FAQ

What is the UVLO behavior of the UCC28501DWTR and how does it differ from other UCC2850x variants?

The UCC28501DWTR features a narrow UVLO threshold of 10.5 V turn-on and 10 V turn-off (0.5 V hysteresis), optimized for fixed-bias operation where VCC is supplied from a regulated rail. This contrasts with UCC28500/UCC28502, which use a wider 16.5 V/10 V threshold for bootstrap startup. The UCC28501DWTR's tight hysteresis prevents erratic cycling during marginal bias conditions and ensures predictable startup in fixed-supply configurations-critical for industrial and medical power supplies where bias stability is paramount. Its UVLO2 stage for the DC-DC section turns on at 6.75 V with 1.2 V hysteresis.

How does the UCC28501DWTR implement line feedforward and why is it important for PFC performance?

The UCC28501DWTR implements line feedforward by mirroring the IAC current into the VFF pin through an external RC filter, generating a voltage proportional to the RMS input line voltage. This VFF signal scales the analog multiplier's gain inversely with the square of line voltage, ensuring constant input power across 85–265 V_RMS inputs. Unlike traditional high-voltage sensing methods, this approach avoids costly isolation components and improves noise immunity. In the UCC28501DWTR, accurate feedforward directly enables near-unity power factor and stable regulation without requiring additional op-amps or precision dividers-reducing bill-of-materials and layout complexity.

Can the UCC28501DWTR support both voltage-mode and current-mode control for the downstream DC-DC converter?

Yes, the UCC28501DWTR supports both control modes for the downstream DC-DC stage. In current-mode configuration-which is the default-the VERR pin receives optocoupler feedback from the secondary side, and ISENSE2 senses peak switch current for cycle-by-cycle limiting. For voltage-mode operation, the CT oscillator ramp is fed back into ISENSE2 via a voltage divider, replacing current sensing with slope-compensated voltage feedback. This flexibility allows designers to select the optimal control strategy based on transformer design, noise environment, and transient response requirements-without changing the UCC28501DWTR itself or adding external mode-select circuitry.

What protection features are integrated into the UCC28501DWTR and how are they activated?

The UCC28501DWTR integrates multiple hardware-based protections: PFC overvoltage lockout triggers if boost output exceeds VREF + 0.5 V (≈8.0 V); zero-power detection disables PFC when VAOUT falls below 0.33 V; pulse-by-pulse current limiting on ISENSE2 trips at 0.94–1.15 V; and OVP/ENBL pin can force full shutdown when pulled below 1.9 V. All protections operate independently of software or external supervision, responding within nanoseconds to microseconds. The UCC28501DWTR also includes thermal foldback via junction temperature derating and UVLO hysteresis to prevent latch-up during brownouts-making it suitable for mission-critical applications where fail-safe behavior is mandatory.

How does the UCC28501DWTR coordinate startup sequencing between the PFC and DC-DC stages?

The UCC28501DWTR coordinates startup automatically: the DC-DC stage remains disabled until the PFC output voltage (monitored via VAOUT and OVP/ENBL) reaches within 10% of its regulation point. Once triggered, SS2 begins charging an external capacitor, ramping the PWM duty cycle linearly to limit inrush current and prevent transformer saturation. If PFC output drops below 74% of nominal (for UCC28501), the DC-DC stage shuts down cleanly. This internal sequencing eliminates the need for external timers or microcontroller intervention, reduces component count, and ensures robust, repeatable startup-even under varying line and load conditions. The entire sequence is implemented in analog hardware for deterministic timing.