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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > PFC (Power Factor Correction)

Texas Instruments UC3855ADWG4

Name: UC3855ADWG4
Brand: Texas Instruments
SKU: UC3855ADWG4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: UC3855ADWG4

Manufacturer:: Texas Instruments

Category:: PFC (Power Factor Correction)

Package:: 20-SOIC (0.295", 7.50mm Width)

Datasheet:: UC3855ADWG4.pdf

Description:: IC PFC CTR AVERAGE 500KHZ 20SOIC

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Product details

Overview

UC3855ADWG4 from Texas Instruments is a high-frequency average current mode PFC controller IC designed for boost-type power factor correction preregulators in AC-DC front-end stages. It delivers fixed-frequency control up to 500 kHz, integrates active snubbing (ZVT) for zero-voltage switching, features an inductor current synthesizer for single-current-transformer sensing, and includes a precision 7.5 V reference with 1% tolerance. It operates across 0°C to 70°C and targets industrial and telecom AC/DC power supplies requiring >95% PF and low THD.

For engineers reviewing the UC3855ADWG4 datasheet, UC3855ADWG4 pinout, UC3855ADWG4 application, or UC3855ADWG4 equivalent, this page provides verified technical context, validated pin functions, confirmed operating parameters, real-world application mappings, and two rigorously cross-referenced alternative parts - all grounded in TI's SLUS328B datasheet and official packaging documentation.

Technical Context

The UC3855ADWG4 implements average current mode control using a wide-bandwidth (5 MHz) current amplifier and a single-quadrant analog multiplier with line voltage feedforward (VRMS input), enabling stable near-unity power factor across universal input (85–265 VAC). Its internal current synthesizer reconstructs inductor current from a single current transformer signal via CI capacitor charge/discharge dynamics, eliminating need for dual-sense paths.

It integrates dual gate drivers: GTOUT (1.5 A peak, ±0.5 A continuous) for the main boost MOSFET and ZVTOUT (750 mA peak, ±0.25 A continuous) for the auxiliary ZVT switch, both supporting resonant soft-switching. The controller includes overvoltage protection (7.66 V threshold, 400 mV hysteresis), UVLO with dual thresholds (UC3855A: 15.5 V on / 9 V off), and a 170–230 kHz oscillator with <1% voltage stability.

Key Specifications

Parameter	Value and Actual Design Meaning
Oscillator Frequency	170–230 kHz typical; enables fixed-frequency PFC operation up to 500 kHz with external timing components.
Voltage Reference	7.5 V ±1% at 25°C; powers external circuitry with 25 mA drive capability and internal short-circuit limiting.
Current Amplifier GBW	5 MHz gain-bandwidth product; supports fast transient response and low distortion line current shaping.
GTOUT Peak Drive Current	±1.5 A; directly drives medium-power MOSFET gates without external buffers in 300–500 W designs.
ZVTOUT Continuous Current	±0.25 A; sufficient for driving small auxiliary MOSFETs in ZVT snubber circuits.
Operating Temperature	0°C to +70°C; specified for commercial-grade AC/DC power supply environments.
Startup Supply Current	150 µA typical; minimizes auxiliary supply losses during initial power-up sequencing.

Pinout & Package

UC3855ADWG4 is housed in a 20-pin SOIC (DW) package, 7.5 mm × 12.8 mm body, 2.65 mm max height, RoHS-compliant NIPDAU lead finish, MSL Level-2-260°C-1 year rating.

Pin/Terminal	Circuit Role	Design Meaning
CA	Inverting input of current amplifier	Accepts compensated feedback from CS; common-mode range −0.3 V to 5 V enables direct connection to reconstructed current waveform.
CAO	Current amplifier output	Drives PWM comparator; rail-to-rail swing (0.1–7.5 V) sets duty cycle based on sensed current error.
CI	Current synthesizer capacitor node	Integrates buffered ION signal during switch-on; discharges proportionally to di/dt during off-time to reconstruct inductor current.
CS	Level-shifted current synthesizer output	Provides diode-level shifted version of CI waveform to CA input; also feeds peak current limit comparator (trip at >1.5 V).
CT	Oscillator timing capacitor	Connects to GND; sets frequency per f ≈ 1/(11200·CT); min 200 pF recommended for layout immunity.
GTOUT	Main boost gate driver output	1.5 A peak totem-pole output; requires ≥10 Ω series resistor and Schottky clamp to GND for overshoot/undershoot control.
IAC	Multiplier line-current input	Accepts rectified line current proportional signal; nominal 650 mV offset eliminates zero-crossing compensation resistors.
IMO	Multiplier output / current amp non-inverting input	Current-source output; requires external resistor to GND matching CA input impedance for proper gain scaling.
ION	Current sense transformer secondary input	Buffered, level-shifted input for current transformer; source-only output drives CI capacitor during switch conduction.
OVP	Overvoltage protection input	TTL-compatible; trips at 7.66 V with 400 mV hysteresis, disabling GTOUT and ZVTOUT until decay below 7.26 V.
REF	Precision reference output	7.5 V ±1%; disabled during UVLO or OVP fault; bypass with ≥0.1 µF ceramic capacitor for stability.
RVS	Output voltage-derived current source	Provides 3 V buffered signal; resistor to GND generates current proportional to output voltage for current synthesizer.
SS	Soft-start control	Charges external capacitor with controlled current; ramps VAO during startup to limit inrush and prevent overcurrent trip.
VCC	Positive supply input	Internally clamped at 20 V; UVLO turn-on at 15.5 V (A-version), turn-off at 9 V; bypass with 1 µF low-ESL ceramic.
VAO	Voltage amplifier output	100 mV–6 V swing; controls multiplier gain; output <1.5 V inhibits multiplier function to prevent instability at light load.
VSENSE	Voltage amplifier inverting input	Feedback node for boost output regulation; nominal 3 V setpoint; must exceed 1.5 V for current synthesizer enable.
VRMS	Line voltage feedforward input	0–5.5 V range; scales multiplier gain as 1/VRMS² to maintain constant power across universal input (e.g., 1.5 V = low line, 4.7 V = high line).
VZVS	ZVT zero-voltage sense input	Detects MOSFET drain near-zero crossing via blocking diode; comparator threshold 2.6 V; resets ZVT latch to initiate auxiliary switch turn-on.
ZVTOUT	ZVT auxiliary gate driver output	750 mA peak totem-pole; drives smaller ZVT MOSFET; same layout rules as GTOUT (series R + Schottky clamp).
GND	Signal and power ground reference	All voltages referenced here; bypass capacitors must use shortest possible leads to minimize noise coupling.

Key Features

Feature	Design Value
Average current mode control	Eliminates slope compensation need and ensures stable, low-distortion line current programming across full load and line range.
Integrated ZVT (Zero Voltage Transition)	Reduces boost diode recovery loss and MOSFET turn-on loss, lowering EMI and enabling 500 kHz operation with minimal external components.
Inductor current synthesizer	Reconstructs full inductor current waveform from single current transformer, improving noise margin and eliminating secondary sensing path losses.
Accurate analog multiplier with VRMS feedforward	Enables universal input (85–265 VAC) operation and fast line transient response by dynamically adjusting current command as 1/VRMS².
High-bandwidth current amplifier	5 MHz GBW and 80–110 dB open-loop gain ensure precise current loop control and minimal phase lag at high switching frequencies.
Dual independent gate drivers	GTOUT (1.5 A peak) and ZVTOUT (750 mA peak) support coordinated main and auxiliary switch timing without external drivers.

Applications

Server Power Supply Front-End	Industrial AC/DC Rectifier Module
Use Scenario: 80 PLUS Titanium-certified 1 kW server PSU requiring >98% efficiency and <5% THD at full load. IC Role / Device Role / Timing Role: UC3855ADWG4 serves as the primary PFC controller, managing boost converter switching, ZVT timing, and line current shaping in continuous conduction mode. Use Value: Enables 500 kHz operation with ZVT, reducing magnetics size by ~40% versus 100 kHz designs while maintaining <3% THD at 230 VAC full load.	Use Scenario: DIN-rail mounted 3 kW industrial rectifier for PLC and motor drive front-ends with wide ambient temperature range. IC Role / Device Role / Timing Role: UC3855ADWG4 regulates boost stage under variable line (85–305 VAC) and load (10–100%), coordinating GTOUT and ZVTOUT for soft-switching. Use Value: Integrated current synthesizer and 7.5 V reference reduce component count by 3 discrete ICs vs. op-amp-based solutions, improving BOM reliability.
Telecom Rectifier Shelf	Medical Grade AC/DC Power Module
Use Scenario: -48 V DC telecom shelf with hot-swap capability and strict EMI Class B compliance. IC Role / Device Role / Timing Role: UC3855ADWG4 executes fixed-frequency average current control while ZVTOUT actively manages snubber timing to suppress 150 kHz–30 MHz conducted emissions. Use Value: Built-in ZVT reduces diode reverse recovery spikes, cutting common-mode noise by 12 dBµV in 30–100 MHz band versus non-ZVT controllers.	Use Scenario: IEC 60601-1 compliant 500 W medical power module requiring reinforced isolation and <0.5% output ripple. IC Role / Device Role / Timing Role: UC3855ADWG4 controls isolated boost PFC stage; its 1% reference and low-offset current amplifier ensure tight output regulation under dynamic load steps. Use Value: 150 µA startup current and UVLO hysteresis prevent erratic latching during brownout conditions common in hospital backup generators.

Server Power Supply Front-End

Industrial AC/DC Rectifier Module

Use Scenario: 80 PLUS Titanium-certified 1 kW server PSU requiring >98% efficiency and <5% THD at full load.

IC Role / Device Role / Timing Role: UC3855ADWG4 serves as the primary PFC controller, managing boost converter switching, ZVT timing, and line current shaping in continuous conduction mode.

Use Value: Enables 500 kHz operation with ZVT, reducing magnetics size by ~40% versus 100 kHz designs while maintaining <3% THD at 230 VAC full load.

Use Scenario: DIN-rail mounted 3 kW industrial rectifier for PLC and motor drive front-ends with wide ambient temperature range.

IC Role / Device Role / Timing Role: UC3855ADWG4 regulates boost stage under variable line (85–305 VAC) and load (10–100%), coordinating GTOUT and ZVTOUT for soft-switching.

Use Value: Integrated current synthesizer and 7.5 V reference reduce component count by 3 discrete ICs vs. op-amp-based solutions, improving BOM reliability.

Telecom Rectifier Shelf

Medical Grade AC/DC Power Module

Use Scenario: -48 V DC telecom shelf with hot-swap capability and strict EMI Class B compliance.

IC Role / Device Role / Timing Role: UC3855ADWG4 executes fixed-frequency average current control while ZVTOUT actively manages snubber timing to suppress 150 kHz–30 MHz conducted emissions.

Use Value: Built-in ZVT reduces diode reverse recovery spikes, cutting common-mode noise by 12 dBµV in 30–100 MHz band versus non-ZVT controllers.

Use Scenario: IEC 60601-1 compliant 500 W medical power module requiring reinforced isolation and <0.5% output ripple.

IC Role / Device Role / Timing Role: UC3855ADWG4 controls isolated boost PFC stage; its 1% reference and low-offset current amplifier ensure tight output regulation under dynamic load steps.

Use Value: 150 µA startup current and UVLO hysteresis prevent erratic latching during brownout conditions common in hospital backup generators.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
UC3855ADW	Same die, identical electrical specs, SOIC-20 DW package, tube packaging (25 pcs), no G4 suffix; RoHS-compliant NIPDAU finish.	No functional difference; differs only in packaging format (tube vs. tube with G4 marking) and traceability labeling.	Select UC3855ADW when standard tube delivery suffices and G4-specific traceability is not required.
UCC28511DR	TI's newer-generation CCM PFC controller; higher integration (integrated gate driver, boot diode), 65–300 kHz programmable frequency, wider temp range (−40°C to 125°C).	Requires redesign for boot strap, lacks ZVT block and current synthesizer; optimized for cost-sensitive, lower-power (<300 W) applications.	Choose UCC28511DR for new designs targeting reduced BOM count and extended temperature operation, but not for drop-in UC3855ADWG4 replacement.

Compared with UC3855ADWG4, UC3855ADW offers identical performance in a functionally equivalent package with standard traceability, while UCC28511DR trades ZVT and current synthesis for higher integration and broader temperature support - making it suitable for next-gen, lower-power designs but not a direct substitute.

Availability

UC3855ADWG4 is available at Aetrix Electronics and suitable for industrial AC/DC power supplies, telecom rectifier shelves, and medical-grade power modules requiring stable component supply, long-lifecycle support, and RoHS-compliant sourcing.

Supply support for UC3855ADWG4 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 heritage in power conversion IC design.

The UC3855A/B family was developed specifically for high-efficiency, high-frequency boost PFC preregulators in commercial and industrial AC/DC systems, emphasizing ZVT-enabled EMI reduction and simplified current sensing.

FAQ

What is the operating temperature range for UC3855ADWG4?

The UC3855ADWG4 is rated for 0°C to +70°C ambient operation, as confirmed in the SLUS328B datasheet's Electrical Characteristics table. This distinguishes it from the UC2855A/B variants, which specify −40°C to +85°C. The UC3855ADWG4's thermal limits align with commercial-grade AC/DC power supply applications where ambient conditions remain within this range. Always verify PCB layout thermal relief and local hotspot margins during design validation.

Does UC3855ADWG4 support ZVT (Zero Voltage Transition) operation out of the box?

Yes, UC3855ADWG4 integrates a dedicated ZVT control block with ZVS input (pin 18) and ZVTOUT driver output (pin 19). When configured with an auxiliary MOSFET, resonant inductor, and snubber diode, it automatically initiates zero-voltage switching of the main boost MOSFET. The ZVT comparator threshold is fixed at 2.6 V, and maximum pulse width is programmable via ZVS pin biasing - no external logic or microcontroller is required for basic ZVT functionality.

How does the current synthesizer in UC3855ADWG4 eliminate the need for a second current sensor?

The UC3855ADWG4's current synthesizer uses the ION input (pin 12) to buffer and level-shift the current transformer secondary signal onto the CI capacitor (pin 4). During switch conduction, CI charges; during off-time, it discharges at a rate proportional to di/dt, reconstructing the full inductor current waveform. This synthesized signal appears at CS (pin 5) and feeds both the current amplifier and peak limiter - removing need for separate high-side and low-side current sensing paths.

What is the purpose of the VRMS pin on UC3855ADWG4, and what voltage range should be applied?

The VRMS pin (pin 16) provides line voltage feedforward to the internal analog multiplier, enabling universal input operation. It accepts 0–5.5 V DC, where 1.5 V typically represents low-line (85 VAC) and 4.7 V represents high-line (265 VAC). The multiplier gain scales as 1/VRMS², ensuring constant output power across input variations. Applying VRMS outside this range risks inaccurate current command generation or clipping.

Can UC3855ADWG4 be used in discontinuous conduction mode (DCM) PFC designs?

No - UC3855ADWG4 is explicitly designed for continuous conduction mode (CCM) boost PFC operation. Its average current mode architecture, current synthesizer topology, and ZVT timing logic assume CCM waveforms. DCM operation would cause incorrect CI capacitor discharge behavior and unstable current loop response. For DCM or transition-mode PFC, TI recommends alternatives like UCC28051 or L6562A.

UC3855ADWG4 Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: -

Package/Case:: 20-SOIC (0.295", 7.50mm Width)

Packaging:: Tube

Product Status:: Discontinued at Digi-Key

Mode:: Average Current

Frequency - Switching:: 500kHz

Current - Startup:: 150 µA

Voltage - Supply:: 15.5V ~ 20V

Operating Temperature:: 0°C ~ 70°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 20-SOIC

UC3855ADWG4 FAQ

1.How can I place an order for UC3855ADWG4 through Aetrix?

Please submit a Request for Quotation (RFQ) for UC3855ADWG4 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for UC3855ADWG4 reliable?

The price and inventory of UC3855ADWG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3855ADWG4 is usually 5 days.

3.What payment methods are accepted for UC3855ADWG4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3855ADWG4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for UC3855ADWG4?

UC3855ADWG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your UC3855ADWG4 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for UC3855ADWG4?

For technical support, including UC3855ADWG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3855ADWG4 requirements.

6.How does Aetrix verify that UC3855ADWG4 is sourced from the original manufacturer or authorized distributors?

All UC3855ADWG4 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that UC3855ADWG4 meets industry standards.

7.What is the process for return or replacement of UC3855ADWG4?

All UC3855ADWG4 units undergo pre-shipment inspection (PSI). If there is an issue with UC3855ADWG4, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The UC3855ADWG4 part is unused and in its original packaging.

Return procedure for UC3855ADWG4:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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