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Texas Instruments UC2855ADW
- Part No.:
- UC2855ADW
- Manufacturer:
- Texas Instruments
- Category:
- PFC (Power Factor Correction)
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
UC2855ADW.pdf
- Description:
- IC PFC CTR AVERAGE 500KHZ 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,163
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Product details
Overview
UC2855ADW 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, and dual gate drivers (GTOUT and ZVTOUT). It operates across −40°C to +85°C and supports switching frequencies up to 500kHz in universal-input AC/DC front-end applications.
For engineers reviewing the UC2855ADW datasheet, UC2855ADW pinout, UC2855ADW application, or UC2855ADW equivalent, this page delivers verified technical context, real-world design meaning of key specs, validated SOIC-20 package mapping, confirmed pin functions per TI SLUS328B, and two rigorously cross-checked alternative parts for PFC control in industrial and telecom power supplies.
Technical Context
The UC2855ADW implements fixed-frequency average current mode control using an internal current amplifier (CA/CAO), voltage amplifier (VSENSE/VAO), and analog multiplier (IAC/VRMS/IMO) to generate precise line-synchronized current commands. Its inductor current synthesizer reconstructs the boost inductor waveform from a single current transformer via CI/CS/ION paths, eliminating need for direct high-side sensing.
ZVT functionality is enabled through ZVS input monitoring and ZVTOUT gate drive, allowing resonant turn-on of auxiliary MOSFETs to reduce diode recovery loss and EMI. The controller features dual UVLO thresholds (15.5V ON / 9V OFF), overvoltage protection with 400mV hysteresis, and soft-start via SS pin with programmable charge/discharge currents.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 160–240 kHz typical; sets PWM timing base - enables stable 500kHz boost operation with external ZVT circuitry. |
| Reference Voltage | 7.5 V ±1% at 25°C; provides stable bias for voltage loop and multiplier - ensures consistent output regulation across line/load. |
| Current Amplifier GBW | 2.5–5 MHz; supports fast transient response in average current loop - critical for low THD under dynamic line conditions. |
| Gate Driver Peak Current | ±1.5 A on GTOUT; drives main boost MOSFET gate directly - eliminates need for external driver stage in ≤1kW designs. |
| ZVTOUT Drive Capability | ±0.75 A peak; drives auxiliary ZVT MOSFET - enables efficient zero-voltage switching without added complexity. |
| Operating Temperature | −40°C to +85°C; qualified for industrial-grade power supply environments - supports convection-cooled server and telecom rectifiers. |
| Startup Supply Current | 150 µA typical; minimizes auxiliary supply burden during cold start - reduces standby loss in high-efficiency PFC stages. |
Pinout & Package
UC2855ADW 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 |
|---|---|---|
| CA | Inverting input of current amplifier | Accepts reconstructed inductor current signal from CS - sets current loop error with CAO feedback network. |
| CAO | Current amplifier output | Drives PWM comparator - directly determines duty cycle based on sensed vs. commanded current. |
| CI | Current synthesizer capacitor node | Integrates ION-buffered signal during switch ON; discharges proportionally to dI/dt during OFF - generates synthetic inductor current waveform. |
| CS | Level-shifted current synthesizer output | Feeds CA input after diode drop - provides clean, noise-immune current sense for average-mode control. |
| CT | Oscillator timing capacitor | Defines PWM frequency via f ≈ 1/(11200·CT) - ceramic cap required for stability up to 500kHz operation. |
| GTOUT | Main boost MOSFET gate driver | ±1.5 A capable totem-pole output - directly drives gate with minimal external components. |
| IAC | Multiplier line-voltage current input | Accepts rectified AC line current proportional signal - enables feedforward-based power regulation across universal input range. |
| IMO | Multiplier output current | Serves as non-inverting input to current amplifier - scales current command by 1/VRMS² for constant power operation. |
| ION | Current transformer secondary input | Buffered, level-shifted input to CI - allows single-turn CT implementation with negligible insertion loss. |
| OVP | Overvoltage protection input | Monitors boost output via resistor divider - disables GTOUT/ZVTOUT within 200 ns if >7.66 V detected. |
| REF | 7.5 V precision reference output | Supplies 25 mA max - powers external circuits (e.g., voltage divider, op-amps) with <15 mV load regulation. |
| RVS | VSENSE buffer output | Provides 3 V nominal buffered signal - forms second input to current synthesizer for output voltage feedforward. |
| SS | Soft-start control | Charges external capacitor with −13 µA current - linearly ramps PWM duty cycle to limit inrush current. |
| VCC | Supply rail | Internally clamped at 20 V; UVLO threshold 15.5 V (ON) / 9 V (OFF) - ensures reliable startup and brownout recovery. |
| VRMS | Line RMS voltage feedforward | Accepts 0–5.5 V signal - enables universal input (85–265 VAC) operation and fast line transient response. |
| VSENSE | Voltage amplifier inverting input | Feedback node for boost output voltage - requires 3 V nominal divider output; must exceed 1.5 V for synthesizer enable. |
| ZVS | ZVT zero-voltage sense input | Detects MOSFET drain near 0 V via blocking diode - triggers ZVTOUT pulse to initiate resonant turn-on. |
| ZVTOUT | ZVT auxiliary MOSFET driver | ±0.75 A peak output - drives smaller auxiliary switch to achieve ZVS, reducing EMI and conduction loss. |
| GND | Signal and power ground | Common reference for all analog/digital functions - requires low-inductance connection to minimize noise coupling. |
Key Features
| Feature | Design Value |
|---|---|
| Average current mode control | Eliminates slope compensation need and achieves <5% THD across full line/load range - enables stable high-power PFC without instability risk. |
| ZVT (Zero Voltage Transition) | Reduces boost diode reverse recovery loss and MOSFET turn-on loss - improves efficiency by 1–2% and lowers EMI emissions in 300–500 kHz designs. |
| Inductor current synthesizer | Reconstructs full inductor current waveform from single current transformer - avoids high-side shunt losses and enables compact, low-noise sensing. |
| Analog multiplier with line compensation | Implements 1/VRMS² feedforward - maintains constant output power across 85–265 VAC input without software or digital calibration. |
| High-bandwidth current amplifier | 5 MHz gain-bandwidth product - supports fast current loop response to line transients, ensuring compliance with IEC 61000-3-2 Class D limits. |
Applications
| Server Power Supply | Industrial AC/DC Rectifier |
|---|---|
|
Use Scenario: 1 kW front-end PFC stage in 1U rack-mounted server PSU with universal AC input and 380 VDC bus. IC Role / Device Role / Timing Role: Primary PFC controller managing boost converter switching, ZVT timing, and line-synchronized current shaping. Use Value: Enables >96% efficiency at full load and meets IEC 61000-3-2 harmonic limits without additional filtering - reduces heatsink size and system cost. |
Use Scenario: 2 kW industrial motor drive input stage operating in harsh ambient (−25°C to +70°C) with wide line variation. IC Role / Device Role / Timing Role: Average-current-mode PFC controller with robust UVLO, OVP, and thermal-stable reference for continuous operation. Use Value: Delivers stable power factor >0.99 across 47–63 Hz and 180–277 VAC - prevents utility penalties and improves grid compatibility. |
| Telecom Rectifier | Medical Imaging Power System |
|
Use Scenario: -48 VDC telecom rectifier with hot-swap capability and strict EMI requirements (CISPR 22 Class B). IC Role / Device Role / Timing Role: High-frequency PFC controller coordinating GTOUT and ZVTOUT to suppress conducted/radiated emissions. Use Value: ZVT operation reduces high-frequency ringing above 30 MHz - simplifies EMI filter design and passes compliance testing on first pass. |
Use Scenario: MRI or CT scanner power supply requiring ultra-low audible noise and zero output voltage droop during imaging bursts. IC Role / Device Role / Timing Role: Precision PFC controller with 1% reference and low-offset amplifiers ensuring stable 400 VDC bus under pulsed loads. Use Value: Soft-start and OVP hysteresis prevent false trips during high dv/dt events - ensures uninterrupted imaging sequences. |
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 architecture and pinout; rated for 0°C to +70°C (vs. UC2855ADW's −40°C to +85°C); identical electrical specs except temp range. | Targeted at commercial-grade systems where extended temperature is not required - e.g., consumer electronics, non-ruggedized telecom. | Select UC3855ADW only when ambient operating temperature stays above 0°C and industrial qualification is unnecessary. |
| UCC28070 | Two-phase interleaved CCM PFC controller; no ZVT support; higher integration (internal oscillator, Vref, drivers); different pinout and control architecture. | Designed for higher-power (>2 kW), lower-EMI applications using dual boost channels - not drop-in compatible with UC2855ADW layouts. | Choose UCC28070 when upgrading to interleaved topology for improved ripple cancellation and thermal distribution - requires PCB redesign. |
Compared with UC3855ADW and UCC28070, the UC2855ADW uniquely combines industrial temperature range, ZVT capability, and single-phase average-current control in SOIC-20 - making it optimal for ruggedized 500–1500 W PFC stages where efficiency, EMI, and reliability are co-prioritized.
Availability
UC2855ADW is available at Aetrix Electronics and suitable for server power supplies, industrial AC/DC rectifiers, telecom rectifiers, and medical imaging power systems requiring stable component supply and long-term industrial temperature support.
Supply support for UC2855ADW 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 UC2855A/B family was engineered specifically for high-efficiency, high-frequency boost PFC preregulators - targeting industrial, telecom, and medical power systems demanding unity power factor, low THD, and robust protection.
FAQ
What is the operating temperature range of the UC2855ADW?
The UC2855ADW is specified for operation from −40°C to +85°C, qualifying it for industrial-grade power supply applications including server PSUs, telecom rectifiers, and motor drives exposed to wide ambient variations. This range is confirmed in the Electrical Characteristics table of TI SLUS328B and distinguishes it from the UC3855ADW (0°C to +70°C). The UC2855ADW maintains full parameter performance across this span, including reference accuracy, amplifier offset, and oscillator stability.
Does the UC2855ADW support ZVT (Zero Voltage Transition) operation?
Yes, the UC2855ADW integrates dedicated ZVT circuitry including ZVS input sensing, ZVTOUT gate driver (±0.75 A peak), and internal logic to enable resonant turn-on of auxiliary switches. As documented in the Description and Block Diagram sections of SLUS328B, this feature reduces MOSFET turn-on loss and diode recovery EMI - enabling practical 500 kHz boost operation. External components (small MOSFET, diode, inductor) are required to complete the ZVT network.
How does the UC2855ADW implement average current mode control without slope compensation?
The UC2855ADW uses an internal current synthesizer that reconstructs the full boost inductor current waveform from a single current transformer (via ION→CI→CS path), feeding a high-bandwidth (5 MHz) current amplifier. This accurate, noise-immune current representation eliminates subharmonic oscillation risk - removing the need for external slope compensation. The technique is explicitly described in the UC2855A/B datasheet under "Inductor Current Synthesizer" and "Average Current Sensing".
What is the purpose of the VRMS and IAC pins on the UC2855ADW?
The VRMS pin accepts a DC voltage proportional to AC input RMS (e.g., 1.5 V at low line, 4.7 V at high line), while IAC receives a current proportional to instantaneous rectified line voltage. Together, they feed the internal analog multiplier to generate a current command scaled by 1/VRMS² - enabling automatic adjustment of current reference across universal input (85–265 VAC) without microcontroller intervention. This is detailed in the Multiplier section and Figure 1 of SLUS328B.
Can the UC2855ADW be used in place of the UC3855ADW?
The UC2855ADW is pin-compatible and functionally identical to the UC3855ADW except for its extended temperature rating (−40°C to +85°C vs. 0°C to +70°C) and part marking. All electrical parameters, pin functions, and application circuits match per TI documentation. Therefore, UC2855ADW may replace UC3855ADW in any design - especially where industrial temperature operation or long-term availability is required. No schematic or layout changes are needed.
UC2855ADW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Mode:
- Average Current
- Frequency - Switching:
- 500kHz
- Current - Startup:
- 150 µA
- Voltage - Supply:
- 15.5V ~ 20V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
UC2855ADW FAQ
1.How can I place an order for UC2855ADW through Aetrix?
Please submit a Request for Quotation (RFQ) for UC2855ADW 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 UC2855ADW reliable?
The price and inventory of UC2855ADW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC2855ADW is usually 5 days.
3.What payment methods are accepted for UC2855ADW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC2855ADW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC2855ADW?
UC2855ADW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC2855ADW 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 UC2855ADW?
For technical support, including UC2855ADW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC2855ADW requirements.
6.How does Aetrix verify that UC2855ADW is sourced from the original manufacturer or authorized distributors?
All UC2855ADW 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 UC2855ADW meets industry standards.
7.What is the process for return or replacement of UC2855ADW?
All UC2855ADW units undergo pre-shipment inspection (PSI). If there is an issue with UC2855ADW, 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 UC2855ADW part is unused and in its original packaging.
Return procedure for UC2855ADW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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