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

Texas Instruments UC2855BN

Name: UC2855BN
Brand: Texas Instruments
SKU: UC2855BN
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: UC2855BN

Manufacturer:: Texas Instruments

Category:: PFC (Power Factor Correction)

Package:: 20-DIP (0.300", 7.62mm)

Datasheet:: UC2855BN.pdf

Description:: IC PFC CTR AV CURR 500KHZ 20DIP

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Product details

Overview

UC2855BN from Texas Instruments is a high-frequency average current-mode PFC controller IC designed for boost-type power factor correction preregulators. It integrates ZVT (Zero Voltage Transition) active snubbing, inductor current synthesizer, analog multiplier with line compensation, 7.5V precision reference (±1%), and dual gate drivers (GTOUT/ZVTOUT) for operation up to 500kHz in industrial AC-DC front-ends.

For engineers reviewing the UC2855BN datasheet, UC2855BN pinout, UC2855BN application, or UC2855BN equivalent, this device supports universal-input (90–264VAC) PFC designs requiring low THD, high efficiency (>95%), EMI reduction via soft-switching, and stable operation across –40°C to +85°C ambient.

Technical Context

The UC2855BN implements fixed-frequency average current mode control using an internal current synthesizer that reconstructs inductor current from a single current sense transformer-eliminating slope compensation and enabling stable operation at high switching frequencies. Its integrated ZVT circuitry senses MOSFET drain voltage via ZVS pin and generates resonant turn-on timing on ZVTOUT to minimize diode recovery loss and MOSFET switching loss.

It features a single-quadrant analog multiplier with VRMS feedforward (0–5.5V range), enabling accurate line-voltage-compensated current programming for near-unity power factor. The voltage amplifier (5MHz GBW, 80dB open-loop gain) and current amplifier (2.5–5MHz GBW, ±4mV offset) provide tight output regulation and fast transient response in closed-loop PFC systems.

Key Specifications

Parameter	Value and Actual Design Meaning
Oscillator Frequency	160–240 kHz typical; sets PWM timing base for boost switch control up to 500kHz with external ZVT circuitry.
Voltage Reference	7.5 V ±1% at 25°C; supplies stable bias for internal amplifiers and enables accurate error amplification.
Current Amplifier GBW	2.5–5 MHz; ensures fast response to input current transients while maintaining stability with standard compensation networks.
Gate Driver Output	±1.5 A peak GTOUT / ±0.75 A peak ZVTOUT; drives main and auxiliary MOSFET gates directly without external buffers.
Operating Temperature	–40°C to +85°C; qualified for industrial-grade AC-DC power supply applications with extended thermal margin.
UVLO Threshold	UC2855B variant: 10.5 V turn-on, 9–10 V turn-off hysteresis; enables reliable startup under brownout conditions.
Multiplier Gain Constant	–0.95 to –0.75 1/V; defines scaling between VRMS feedforward and current command signal for universal input operation.

Pinout & Package

UC2855BN is housed in a 20-pin Plastic Dual In-line Package (PDIP-N), 0.300-inch wide body, with standard DIL-20 pinout compatible with JEDEC MS-001. Pin numbering follows top-view orientation with Pin 1 marked by notch or dot.

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 current-sense network.
CAO	Current amplifier output	Drives PWM comparator; rail-to-rail swing (0.1–7.5 V) provides full-duty-cycle control authority over GTOUT.
CI	Current synthesizer capacitor node	Integrates buffered ION signal during switch ON; discharges at rate proportional to dI/dt during OFF to reconstruct inductor current waveform.
CS	Level-shifted current synthesizer output	Provides reconstructed current signal to CA/CAO; also feeds peak-limit comparator (trip >1.5 V disables GTOUT).
CT	Oscillator timing capacitor	Connects to GND; sets frequency per f ≈ 1/(11200·CT); min 200 pF recommended for layout immunity and accuracy.
GTOUT	Main boost MOSFET gate driver	1.5 A peak totem-pole output; requires ≥10 Ω series resistor and Schottky clamp to GND for overshoot/undershoot control.
IAC	Multiplier current input	Accepts rectified line current proportional signal; nominal 650 mV DC offset eliminates zero-crossing compensation resistors.
IMO	Multiplier output	Current-source output; connects to CA via resistor matching current amplifier input impedance for proper gain setting.
ION	Current sense transformer input	Buffered input for secondary-side current transformer; source-only output drives CI capacitor during switch ON time.
OVP	Overvoltage protection input	TTL-compatible; trips at 7.5–7.66 V with 200–600 mV hysteresis; disables both GTOUT and ZVTOUT until decay below threshold.
REF	Precision 7.5 V reference output	Supplies 25 mA max; disabled during UVLO or OVP fault; requires ≥0.1 µF ceramic bypass to GND for stability.
RVS	Output voltage sensing buffer	Provides 3 V nominal buffered signal; used as second input to current synthesizer for output-voltage-dependent current shaping.
SS	Soft-start control	Charges external capacitor with controlled current; ramps VAO during startup to limit inrush and ensure monotonic duty-cycle increase.
VAO	Voltage amplifier output	100 mV–6 V swing; serves as multiplier input; <1.5 V inhibits multiplier output, preventing erroneous current commands at low load.
VCC	Positive supply rail	Internally clamped to 20 V; 15.5 V (A) or 10.5 V (B) turn-on threshold; 150 µA typical startup current reduces no-load loss.
VRMS	Line voltage feedforward input	0–5.5 V range; scales multiplier gain as 1/VRMS² to maintain constant power delivery across universal AC inputs.
VSENSE	Voltage amplifier inverting input	Feedback node for output voltage divider; nominal 3 V setpoint; must exceed 1.5 V (25°C) for current synthesizer to function.
ZVS	ZVT zero-voltage sense input	Detects ≈0 V drain voltage via blocking diode; resets ZVT latch when level drops below 2.6 V threshold.
ZVTOUT	ZVT auxiliary MOSFET driver	750 mA peak totem-pole output; drives smaller ZVT switch; supports synchronization use with external timing signals.
GND	Signal and power ground reference	All voltages referenced here; bypass capacitors must connect with shortest possible leads to minimize noise coupling.

Key Features

Feature	Design Value
ZVT Active Snubbing	Reduces MOSFET turn-on loss and diode reverse-recovery stress, enabling 500kHz operation with lower EMI and higher system efficiency.
Inductor Current Synthesizer	Reconstructs full inductor current waveform from single current transformer, eliminating need for high-side shunt and improving noise immunity.
Line-Compensated Analog Multiplier	Uses VRMS feedforward (0–5.5V) to scale current command as 1/VRMS², ensuring stable PFC across 90–264VAC universal input range.
High-Bandwidth Current Amplifier	2.5–5 MHz gain-bandwidth product with ±4 mV offset enables fast current loop response and low THD (<5%) at full load.
Dual Independent Gate Drivers	GTOUT (±1.5 A peak) and ZVTOUT (±0.75 A peak) support separate main and auxiliary switch control without external drivers.

Applications

Server Power Supply	Industrial Motor Drive Input Stage
Use Scenario: 1U/2U AC-DC front-end in 80 PLUS Titanium-certified server PSUs delivering 1–3 kW with <5% THD. IC Role / Device Role / Timing Role: Primary PFC controller managing boost stage; regulates input current waveform to match sinusoidal voltage with near-unity PF. Use Value: Enables 500kHz ZVT operation, reducing magnetics size by 40% and lowering conducted EMI to meet CISPR-32 Class A limits without added filtering.	Use Scenario: Three-phase rectified input stage in variable-frequency drive (VFD) with regenerative braking capability. IC Role / Device Role / Timing Role: Boost PFC controller operating from 380–480VDC bus; maintains stable DC link voltage during regeneration events. Use Value: UVLO hysteresis (10.5 V on / 9 V off) prevents nuisance tripping during line sags; OVP lockout protects downstream IGBTs from overvoltage faults.
Medical Imaging Power System	Telecom Rectifier Shelf
Use Scenario: High-reliability PFC stage in CT/MRI scanner power supply requiring >96% efficiency and <3% THD at full load. IC Role / Device Role / Timing Role: Average current-mode PFC controller with precise 7.5 V reference (±1%) and low-offset amplifiers for tight regulation. Use Value: 2.5–5 MHz current amplifier GBW ensures sub-100 µs current loop response, critical for handling rapid load steps during X-ray pulse generation.	Use Scenario: 48 V telecom rectifier module supporting -48 VDC output with hot-swap and redundancy management. IC Role / Device Role / Timing Role: PFC controller interfacing with digital PMBus supervisor; uses OVP/EN pins for remote shutdown and fault signaling. Use Value: TTL-compatible OVP pin (7.5 V trip, 400 mV hysteresis) enables direct interface with FPGA-based supervision logic without level-shifting.

Server Power Supply

Industrial Motor Drive Input Stage

Use Scenario: 1U/2U AC-DC front-end in 80 PLUS Titanium-certified server PSUs delivering 1–3 kW with <5% THD.

IC Role / Device Role / Timing Role: Primary PFC controller managing boost stage; regulates input current waveform to match sinusoidal voltage with near-unity PF.

Use Value: Enables 500kHz ZVT operation, reducing magnetics size by 40% and lowering conducted EMI to meet CISPR-32 Class A limits without added filtering.

Use Scenario: Three-phase rectified input stage in variable-frequency drive (VFD) with regenerative braking capability.

IC Role / Device Role / Timing Role: Boost PFC controller operating from 380–480VDC bus; maintains stable DC link voltage during regeneration events.

Use Value: UVLO hysteresis (10.5 V on / 9 V off) prevents nuisance tripping during line sags; OVP lockout protects downstream IGBTs from overvoltage faults.

Medical Imaging Power System

Telecom Rectifier Shelf

Use Scenario: High-reliability PFC stage in CT/MRI scanner power supply requiring >96% efficiency and <3% THD at full load.

IC Role / Device Role / Timing Role: Average current-mode PFC controller with precise 7.5 V reference (±1%) and low-offset amplifiers for tight regulation.

Use Value: 2.5–5 MHz current amplifier GBW ensures sub-100 µs current loop response, critical for handling rapid load steps during X-ray pulse generation.

Use Scenario: 48 V telecom rectifier module supporting -48 VDC output with hot-swap and redundancy management.

IC Role / Device Role / Timing Role: PFC controller interfacing with digital PMBus supervisor; uses OVP/EN pins for remote shutdown and fault signaling.

Use Value: TTL-compatible OVP pin (7.5 V trip, 400 mV hysteresis) enables direct interface with FPGA-based supervision logic without level-shifting.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
UC3855BN	Same pinout and architecture but rated for 0°C to +70°C; lower UVLO turn-on (10.5 V) matches UC2855BN B-version; no functional difference in ZVT or current synthesis.	Targeted at commercial-temperature applications; not qualified for extended industrial temperature range (–40°C to +85°C).	Select UC3855BN only if ambient operating temperature remains within 0–70°C and industrial qualification is unnecessary.
UCC28511N	Single-ended PFC controller with integrated 600 V startup regulator; lacks ZVT circuitry and current synthesizer; uses conventional shunt-based current sensing.	Designed for cost-sensitive, lower-power (<500 W) PFC stages without soft-switching requirements; no VRMS feedforward multiplier.	Choose UCC28511N for simplified design where ZVT efficiency gains are non-critical and thermal derating allows wider ambient tolerance.

Compared with UC3855BN and UCC28511N, UC2855BN delivers extended temperature operation, ZVT-enabled high-frequency efficiency, and current synthesizer-based noise-immune sensing-making it optimal for high-reliability industrial and medical PFC designs demanding >95% efficiency and <5% THD.

Availability

UC2855BN is available at Aetrix Electronics and suitable for server power supplies, industrial motor drive input stages, medical imaging power systems, and telecom rectifier shelves requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for UC2855BN 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 power conversion IC expertise.

The UC2855x family was engineered specifically for high-efficiency, high-frequency active PFC in industrial and computing power supplies-emphasizing ZVT soft-switching, universal input operation, and robust protection integration.

FAQ

What is the operating temperature range of the UC2855BN?

The UC2855BN is specified for operation from –40°C to +85°C ambient temperature. This extended industrial temperature rating distinguishes it from the UC3855BN (0°C to +70°C) and makes it suitable for high-reliability applications such as medical imaging equipment and industrial motor drives where thermal margins are critical. The datasheet confirms this range applies to both UC2855A/B variants, and UC2855BN corresponds to the B-version UVLO threshold.

Does the UC2855BN require external slope compensation?

No, the UC2855BN does not require external slope compensation. Its average current mode control architecture-combined with the internal current synthesizer that reconstructs inductor current from a single current sense transformer-provides inherent stability across the full duty cycle range. This eliminates the need for slope compensation components and simplifies PCB layout compared to peak current mode controllers.

How does the UC2855BN implement Zero Voltage Transition (ZVT)?

The UC2855BN implements ZVT by monitoring the main MOSFET drain voltage via the ZVS pin. When the voltage falls to ≈0.7 V (indicating near-zero drain-source voltage), the internal ZVT comparator resets the ZVT latch and triggers ZVTOUT to drive the auxiliary ZVT MOSFET. This initiates resonant turn-on, reducing switching losses and EMI. The ZVTOUT driver delivers ±0.75 A peak current and supports programmable pulse width via ZVS pin configuration.

What is the purpose of the VRMS pin on the UC2855BN?

The VRMS pin on the UC2855BN accepts a voltage proportional to the RMS value of the rectified AC input (typically 1.5 V at low line, 4.7 V at high line). It feeds the analog multiplier to scale the current command as 1/VRMS²-ensuring constant output power across universal input voltages (90–264 VAC) without manual reconfiguration. The pin accepts 0–5.5 V and enables fast line transient response in PFC preregulators.

Can the UC2855BN be used with a current sense shunt instead of a transformer?

Yes, the UC2855BN supports both current sense transformer and resistive shunt methods. The datasheet explicitly states "average current sensing can be employed using a simple resistive shunt or a current sense transformer." When using a shunt, connect it between the boost switch source and GND, feed the differential voltage into CA/CS via appropriate scaling, and disable the current synthesizer path by leaving ION open or grounding it per application note U-153 guidance.

UC2855BN Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: -

Package/Case:: 20-DIP (0.300", 7.62mm)

Packaging:: Bulk

Product Status:: Obsolete

Mode:: Average Current

Frequency - Switching:: 500kHz

Current - Startup:: 150 µA

Voltage - Supply:: 10.5V ~ 20V

Operating Temperature:: -40°C ~ 85°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 20-PDIP

UC2855BN FAQ

1.How can I place an order for UC2855BN through Aetrix?

Please submit a Request for Quotation (RFQ) for UC2855BN 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 UC2855BN reliable?

The price and inventory of UC2855BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC2855BN is usually 5 days.

3.What payment methods are accepted for UC2855BN?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC2855BN transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for UC2855BN?

UC2855BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your UC2855BN 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 UC2855BN?

For technical support, including UC2855BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC2855BN requirements.

6.How does Aetrix verify that UC2855BN is sourced from the original manufacturer or authorized distributors?

All UC2855BN 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 UC2855BN meets industry standards.

7.What is the process for return or replacement of UC2855BN?

All UC2855BN units undergo pre-shipment inspection (PSI). If there is an issue with UC2855BN, 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 UC2855BN part is unused and in its original packaging.

Return procedure for UC2855BN:

1.Submit a request within 90 days.

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

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