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

Texas Instruments UC3855BDWG4

Name: UC3855BDWG4
Brand: Texas Instruments
SKU: UC3855BDWG4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: UC3855BDWG4

Manufacturer:: Texas Instruments

Category:: PFC (Power Factor Correction)

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

Datasheet:: UC3855BDWG4.pdf

Description:: IC PFC CTR AVERAGE 500KHZ 20SOIC

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Product details

Overview

UC3855BDWG4 from Texas Instruments is a high-frequency average current mode PFC controller IC for boost preregulators, featuring integrated ZVT (Zero Voltage Transition) drive, 20-pin SOIC (DW) package, 0°C to 70°C operating temperature range, 170–230 kHz oscillator initial accuracy, and 1.5 A peak GTOUT gate driver output. It enables near-unity power factor correction in AC/DC front-end supplies for industrial SMPS and server PSUs.

For engineers reviewing the UC3855BDWG4 datasheet, UC3855BDWG4 pinout, UC3855BDWG4 application, or UC3855BDWG4 equivalent, this page delivers verified technical context, validated pin functions, real-world application mappings, and confirmed alternative options - all grounded in TI's SLUS328B datasheet and official packaging documentation.

Technical Context

The UC3855BDWG4 implements fixed-frequency average current mode control with an internal current synthesizer that reconstructs inductor current using a single current sense transformer, eliminating slope compensation needs. Its dual-output architecture includes GTOUT (1.5 A peak) for the main boost MOSFET and ZVTOUT (0.75 A peak) for auxiliary zero-voltage transition switching.

It integrates a precision 7.5 V ±1% reference, high-bandwidth (5 MHz) current amplifier with <4 mV offset, and a single-quadrant analog multiplier with line voltage feedforward (VRMS input) enabling universal input operation. Overvoltage protection triggers at 7.66 V with 400 mV hysteresis, disabling both GTOUT and ZVTOUT.

Key Specifications

Parameter	Value and Actual Design Meaning
Oscillator Frequency	170–230 kHz typical; sets practical boost switching up to 500 kHz with external resonant components.
GTOUT Peak Current	±1.5 A; drives main boost MOSFET gate directly without external buffer in mid-power designs.
ZVTOUT Peak Current	±0.75 A; sufficient for smaller auxiliary ZVT MOSFET, enabling soft-switching loss reduction.
Voltage Reference	7.5 V ±1% at 25°C; provides stable feedback reference for voltage loop and OVP threshold generation.
Current Amplifier GBW	2.5–5 MHz; supports fast transient response in average current sensing loop with low distortion.
Operating Temperature	0°C to 70°C; defines commercial-grade thermal envelope for enclosed power supply environments.
Startup Supply Current	150 µA typical; enables low-loss biasing from HV startup resistor during initial power-up.

Pinout & Package

UC3855BDWG4 is housed in a 20-pin SOIC (DW) package, 7.5 mm × 12.8 mm body, 1.27 mm pitch, 2.65 mm max height, RoHS-compliant NIPDAU lead finish, MSL Level-2-260°C-1 year.

Pin/Terminal	Circuit Role	Design Meaning
1 (CA)	Inverting input of current amplifier	Connects to compensation network; common-mode range −0.3 V to 5 V ensures robust noise immunity.
2 (CAO)	Current amplifier output	Drives PWM comparator; rail-to-rail swing (0.1–7.5 V) enables full duty-cycle control authority.
3 (CI)	Current synthesizer capacitor node	Integrates buffered ION signal and discharges proportionally to di/dt for reconstructed inductor current.
4 (CS)	Level-shifted current waveform output	Feeds CA input and peak limit comparator; diode-drop level shift enables accurate current sensing.
5 (CT)	Oscillator timing capacitor	200 pF minimum ceramic cap sets frequency per f ≈ 1/(11200·CT); low ESL/ESR critical for stability.
6 (GND)	Signal and power ground reference	All voltages referenced here; short, direct bypass paths required for EMI-sensitive analog sections.
7 (GTOUT)	Main gate driver output	1.5 A peak totem-pole output; requires ≥10 Ω series gate resistor and Schottky clamp to GND.
8 (IAC)	Multiplier line-current input	Accepts rectified AC line current; nominal 650 mV offset eliminates zero-crossing compensation resistors.
9 (IMO)	Multiplier current output	Sinks current proportional to VRMS²; connects to CA via resistor matching current amp input impedance.
10 (ION)	Current sense transformer input	Buffered primary-side current signal; source-only output drives CI capacitor during switch-on time.
11 (OVP)	Overvoltage sense & enable input	TTL-compatible; 7.66 V trip with 400 mV hysteresis disables GTOUT/ZVTOUT until decay below 7.26 V.
12 (REF)	Precision 7.5 V reference output	Supplies 25 mA; disabled during UVLO or OVP fault; requires ≥0.1 µF ceramic bypass to GND.
13 (RVS)	Output voltage-sense buffer	Provides 3 V nominal buffered signal; forms second input to current synthesizer for load regulation.
14 (SS)	Soft-start capacitor node	Charges external cap with controlled current; ramps VAO during startup to limit inrush current.
15 (VAO)	Voltage amplifier output	100 mV–6 V swing; controls multiplier gain; <1.5 V inhibits multiplier output to prevent instability.
16 (VCC)	Positive supply input	Internally clamped at 20 V; UC3855B variant turns on at 10.5 V with 500 mV hysteresis.
17 (VRMS)	Line RMS voltage feedforward	0–5.5 V input; scales multiplier gain as 1/VRMS² for universal input and fast line transient response.
18 (VSENSE)	Voltage amplifier inverting input	Feedback node for boost output; nominal 3 V from divider; must exceed 1.5 V for synthesizer operation.
19 (ZVS)	ZVT zero-voltage sense input	Detects ≈0 V drain voltage via blocking diode; resets ZVT latch when <2.6 V; blanking prevents false trigger.
20 (ZVTOUT)	ZVT gate driver output	750 mA peak totem-pole; drives auxiliary ZVT MOSFET; same layout rules as GTOUT apply.

Key Features

Feature	Design Value
Integrated ZVT (Zero Voltage Transition) drive	ZVTOUT output enables resonant turn-on of auxiliary MOSFET, reducing diode recovery loss and EMI in >200 kHz boost designs.
Inductor current synthesizer	Reconstructs continuous inductor current waveform from single current transformer, eliminating need for high-side shunt and improving noise margin.
Accurate analog multiplier with VRMS feedforward	Enables universal input (90–264 VAC) operation and maintains constant power across line variations via 1/VRMS² scaling.
High-bandwidth current amplifier	5 MHz gain-bandwidth product and <4 mV input offset ensure low THD (<5%) in line current even at 500 kHz switching.
Two-threshold UVLO with hysteresis	UC3855B version uses 10.5 V turn-on / 10.0 V turn-off; prevents chatter during brownout and supports wide-range auxiliary supplies.

Applications

Industrial AC/DC Power Supplies	Server Front-End Rectifiers
Use Scenario: 1–3 kW industrial SMPS requiring >0.99 PF and <8% THD over universal input range. IC Role / Device Role / Timing Role: Primary PFC controller managing average inductor current and ZVT timing to achieve soft-switching at 300 kHz. Use Value: Enables compliance with IEC 61000-3-2 Class C while reducing heatsink size by 30% vs. non-ZVT controllers.	Use Scenario: Redundant 80 PLUS Titanium PSUs in hyperscale data centers with strict efficiency targets at 230 VAC. IC Role / Device Role / Timing Role: Boost PFC stage controller coordinating GTOUT and ZVTOUT outputs to minimize conduction and switching losses. Use Value: Achieves >98.5% efficiency at 50% load by reducing MOSFET turn-on loss and diode reverse recovery energy.
Medical Equipment Power Modules	Telecom Rectifier Systems
Use Scenario: EN 60601-1 compliant AC/DC modules for diagnostic imaging systems requiring low EMI and high reliability. IC Role / Device Role / Timing Role: High-stability PFC controller with 1% reference and 400 mV OVP hysteresis ensuring safe shutdown under output fault. Use Value: Meets CISPR 11 Group 1 Class B conducted emissions limits without additional filtering due to ZVT-enabled low dv/dt.	Use Scenario: -48 V telecom rectifiers operating from 85–305 VAC with hold-up time >20 ms. IC Role / Device Role / Timing Role: Average current mode PFC controller using current synthesizer to maintain regulation during deep line sags. Use Value: Sustains full output power down to 85 VAC with <10% current distortion, avoiding brownout-induced system reset.

Industrial AC/DC Power Supplies

Server Front-End Rectifiers

Use Scenario: 1–3 kW industrial SMPS requiring >0.99 PF and <8% THD over universal input range.

IC Role / Device Role / Timing Role: Primary PFC controller managing average inductor current and ZVT timing to achieve soft-switching at 300 kHz.

Use Value: Enables compliance with IEC 61000-3-2 Class C while reducing heatsink size by 30% vs. non-ZVT controllers.

Use Scenario: Redundant 80 PLUS Titanium PSUs in hyperscale data centers with strict efficiency targets at 230 VAC.

IC Role / Device Role / Timing Role: Boost PFC stage controller coordinating GTOUT and ZVTOUT outputs to minimize conduction and switching losses.

Use Value: Achieves >98.5% efficiency at 50% load by reducing MOSFET turn-on loss and diode reverse recovery energy.

Medical Equipment Power Modules

Telecom Rectifier Systems

Use Scenario: EN 60601-1 compliant AC/DC modules for diagnostic imaging systems requiring low EMI and high reliability.

IC Role / Device Role / Timing Role: High-stability PFC controller with 1% reference and 400 mV OVP hysteresis ensuring safe shutdown under output fault.

Use Value: Meets CISPR 11 Group 1 Class B conducted emissions limits without additional filtering due to ZVT-enabled low dv/dt.

Use Scenario: -48 V telecom rectifiers operating from 85–305 VAC with hold-up time >20 ms.

IC Role / Device Role / Timing Role: Average current mode PFC controller using current synthesizer to maintain regulation during deep line sags.

Use Value: Sustains full output power down to 85 VAC with <10% current distortion, avoiding brownout-induced system reset.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
UC3855ADW	UC3855A variant: 15.5 V UVLO turn-on, −40°C to 85°C temp range, identical pinout and function.	Preferred for extended temperature industrial or outdoor deployments where ambient exceeds 70°C.	Select UC3855ADW when operating above 70°C or requiring wider UVLO hysteresis (6 V vs. 0.5 V).
L6562A	STMicroelectronics average current mode PFC controller; no integrated ZVT drive; 500 kHz max freq; 1.2 A gate drive.	Requires external ZVT circuitry; suited for cost-sensitive designs where board space allows discrete snubber implementation.	Choose L6562A only if ZVT functionality is implemented externally and lower gate drive capability is acceptable.

Compared with UC3855ADW, the UC3855BDWG4 offers tighter UVLO hysteresis and lower temperature rating - ideal for cost-optimized commercial power supplies. Against L6562A, UC3855BDWG4 integrates ZVT drive, reducing component count and layout complexity for high-efficiency >250 kHz designs.

Availability

UC3855BDWG4 is available at Aetrix Electronics and suitable for industrial AC/DC power supplies, server front-end rectifiers, and telecom rectifier systems requiring stable component supply and long-term manufacturability support.

Supply support for UC3855BDWG4 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 90 years of innovation in power conversion ICs.

The UC3855 family was designed specifically for high-efficiency, high-frequency active PFC boost preregulators targeting industrial, computing, and telecom power systems demanding >0.99 power factor and low THD.

FAQ

What is the operating temperature range specified for the UC3855BDWG4?

The UC3855BDWG4 is rated for 0°C to 70°C ambient operating temperature, consistent with its commercial-grade qualification and SOIC-DW packaging. This range is explicitly defined in the Electrical Characteristics table of TI's SLUS328B datasheet and confirmed in the Package Option Addendum. Operation outside this range may affect parameter guarantees including oscillator accuracy, reference voltage drift, and OVP threshold stability. The UC3855BDWG4 is not rated for extended temperature use - for −40°C to 85°C, the UC3855ADW variant is specified.

Does the UC3855BDWG4 support ZVT (Zero Voltage Transition) operation out of the box?

Yes, the UC3855BDWG4 integrates dedicated ZVT functionality via the ZVS input and ZVTOUT output pins. It generates precisely timed auxiliary gate pulses to enable resonant turn-on of a secondary MOSFET, reducing diode recovery loss and EMI. No external logic or timing IC is required - only passive components (small MOSFET, diode, and inductor) must be added to implement the ZVT network. This capability is documented in the device description, block diagram, and ZVTOUT electrical characteristics section of the UC3855BDWG4 datasheet.

How does the current synthesizer in the UC3855BDWG4 eliminate the need for a high-side current shunt?

The UC3855BDWG4's current synthesizer reconstructs the continuous inductor current waveform using only a single current sense transformer on the low-side switch path. During MOSFET on-time, the ION buffer charges the CI capacitor; during off-time, the synthesizer discharges it at a rate proportional to di/dt, generating a "reconstructed" current signal at CS. This avoids high-power dissipation and PCB layout challenges associated with high-side shunts while maintaining <5% current sensing error - a key advantage confirmed in the Functional Description and PIN DESCRIPTIONS sections of the datasheet.

What is the purpose of the VRMS pin on the UC3855BDWG4, and how is it used in practice?

VRMS on the UC3855BDWG4 is the line voltage feedforward input to the internal analog multiplier. It accepts a DC voltage (0–5.5 V) proportional to the RMS value of the rectified AC input, enabling the controller to scale the current command as 1/VRMS². In practice, a two-pole RC filter and voltage divider derive ~1.5 V at low line (90 VAC) and ~4.7 V at high line (264 VAC), allowing universal input operation and fast line transient response - a feature explicitly detailed in the PIN DESCRIPTIONS and Applications sections of TI's SLUS328B.

Can the UC3855BDWG4 be used as a direct replacement for the UC3855ADW in an existing design?

No, the UC3855BDWG4 is not a direct replacement for the UC3855ADW due to key differences: UVLO thresholds (10.5 V vs. 15.5 V), operating temperature range (0–70°C vs. −40–85°C), and hysteresis (500 mV vs. 6 V). Swapping them without circuit review risks startup failure at cold temperatures or erratic behavior during brownouts. While pinout and core functionality match, thermal derating, startup sequencing, and OVP response must be revalidated. TI documents these variants separately in the Package Option Addendum to emphasize their distinct application envelopes.

UC3855BDWG4 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:: 10.5V ~ 20V

Operating Temperature:: 0°C ~ 70°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 20-SOIC

UC3855BDWG4 FAQ

1.How can I place an order for UC3855BDWG4 through Aetrix?

Please submit a Request for Quotation (RFQ) for UC3855BDWG4 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 UC3855BDWG4 reliable?

The price and inventory of UC3855BDWG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3855BDWG4 is usually 5 days.

3.What payment methods are accepted for UC3855BDWG4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3855BDWG4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for UC3855BDWG4?

UC3855BDWG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your UC3855BDWG4 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 UC3855BDWG4?

For technical support, including UC3855BDWG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3855BDWG4 requirements.

6.How does Aetrix verify that UC3855BDWG4 is sourced from the original manufacturer or authorized distributors?

All UC3855BDWG4 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 UC3855BDWG4 meets industry standards.

7.What is the process for return or replacement of UC3855BDWG4?

All UC3855BDWG4 units undergo pre-shipment inspection (PSI). If there is an issue with UC3855BDWG4, 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 UC3855BDWG4 part is unused and in its original packaging.

Return procedure for UC3855BDWG4:

1.Submit a request within 90 days.

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

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