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Texas Instruments UC2855BDW
- Part No.:
- UC2855BDW
- Manufacturer:
- Texas Instruments
- Category:
- PFC (Power Factor Correction)
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
UC2855BDW.pdf
- Description:
- IC PFC CTR AVERAGE 500KHZ 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,267
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Product details
Overview
UC2855BDW from Texas Instruments is a high-frequency average current-mode PFC controller IC for boost preregulators, featuring integrated ZVT (Zero Voltage Transition) active snubbing, 7.5V ±1% reference, 5MHz current amplifier bandwidth, and operation up to 500kHz in industrial-grade (−40°C to +85°C) applications such as server power supplies and industrial AC-DC front-ends.
For engineers reviewing the UC2855BDW datasheet, UC2855BDW pinout, UC2855BDW application, or UC2855BDW equivalent, key selection criteria include its dual-gate drive capability (GTOUT/ZVTOUT), inductor current synthesizer for transformer-based sensing, line-compensated analog multiplier, OVP/UVLO hysteresis thresholds, and SOIC-20 package compatibility with high-density PFC board layouts.
Technical Context
The UC2855BDW implements fixed-frequency average current mode control using an internal current synthesizer that reconstructs inductor current from a single current sense transformer signal on CI, eliminating slope compensation needs. Its single-quadrant analog multiplier accepts VRMS and VAOUT inputs to generate a line-compensated current command proportional to 1/VRMS².
ZVT functionality is enabled via ZVS input monitoring and ZVTOUT gate drive, supporting resonant soft-switching of auxiliary MOSFETs to reduce diode recovery loss and EMI. The voltage amplifier features 80dB open-loop gain and soft-start integration via SS pin, while OVP protection disables both GTOUT and ZVTOUT with 400mV hysteresis when VSENSE-derived feedback exceeds 7.66V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 160–240 kHz typical; sets PFC switching frequency via CT capacitor, enabling stable operation up to 500 kHz with external ZVT components. |
| Reference Voltage | 7.5 V ±1%; provides precision bias for voltage amplifier and multiplier circuits, ensuring accurate output regulation across temperature. |
| Current Amplifier BW | 5 MHz typical; enables fast transient response to input current changes without instability, critical for low THD line current shaping. |
| VCC UVLO Threshold | 10.5–10.8 V turn-on, 9–10 V turn-off; supports reliable startup under brownout conditions with 500 mV hysteresis for noise immunity. |
| OVP Threshold | 7.5–7.66 V with 200–600 mV hysteresis; triggers latch-off of GTOUT/ZVTOUT to protect boost stage during overvoltage faults. |
| Gate Drive Peak Current | ±1.5 A on GTOUT, ±0.75 A on ZVTOUT; drives main and auxiliary MOSFET gates directly without external buffers in most designs. |
| Operating Temp Range | −40°C to +85°C; qualified for industrial environments where ambient thermal stress impacts long-term PFC reliability. |
Pinout & Package
UC2855BDW is housed in a 20-pin SOIC (DW) package, 7.5 mm × 12.8 mm body size, 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 |
|---|---|---|
| GTOUT | Main boost switch gate driver output | 1.5A peak totem-pole output driving primary MOSFET; requires ≥10Ω series gate resistor and Schottky clamp to GND. |
| ZVTOUT | Zero-voltage transition auxiliary switch driver | 750mA peak output for resonant snubber MOSFET; enables soft-switching to reduce EMI and conduction losses. |
| CI | Current synthesizer capacitor node | Integrates buffered ION signal during switch ON and discharges proportionally to di/dt during OFF to reconstruct inductor current. |
| CS | Level-shifted reconstructed current output | Diode-level shifted version of CI waveform fed to CA input; used for average current sensing and peak limiting at >1.5V. |
| VSENSE | Inverting input of voltage amplifier | Feedback node for boost output voltage regulation; requires 3V nominal divider output and >1.5V minimum for synthesizer enable. |
| VRMS | Line voltage feedforward input | Accepts 0–5.5V RMS-scaled signal to adjust multiplier gain as 1/VRMS², enabling universal input (90–264VAC) operation. |
| OVP | Hysteretic overvoltage sense input | Monitors boosted DC bus via resistor divider; trips at 7.66V with 400mV hysteresis to disable both gate drivers until decay below 7.26V. |
| SS | Soft-start voltage ramp node | Charges external capacitor with −13µA current source; controls PWM duty cycle ramp-up to limit inrush current during startup. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated ZVT control | Reduces boost diode reverse recovery loss and MOSFET turn-on loss via resonant auxiliary switching, lowering system EMI and improving efficiency above 250kHz. |
| Inductor current synthesizer | Enables single current transformer sensing by reconstructing full inductor waveform on CI/CS pins-eliminates shunt resistor losses and improves noise margin. |
| Line-compensated analog multiplier | Uses VRMS and VAOUT inputs to generate precise current command proportional to 1/VRMS², maintaining near-unity PF across universal AC input range. |
| High-bandwidth current amplifier | 5MHz gain-bandwidth product and 80dB open-loop gain ensure fast, stable current loop response with minimal phase lag at high switching frequencies. |
| Dual independent gate drivers | GTOUT (±1.5A) and ZVTOUT (±0.75A) support discrete main/auxiliary MOSFETs without external drivers, simplifying layout and reducing BOM count. |
Applications
| Server Power Supply Front-End | Industrial Motor Drive Input Stage |
|---|---|
Use Scenario: 3kW redundant AC-DC rectification in data center PSUs requiring >98% efficiency and EN61000-3-2 Class A compliance. IC Role / Device Role / Timing Role: Primary PFC controller managing boost converter switching, ZVT timing, and line-current shaping via average current mode control. Use Value: Enables 500kHz operation with low THD (<5%) and reduced heatsink requirements due to ZVT-assisted soft-switching and high-efficiency current sensing. | Use Scenario: 7.5kW variable-frequency drive input stage operating in harsh factory environments with wide input voltage variation (85–264VAC). IC Role / Device Role / Timing Role: Industrial-grade PFC regulator providing regulated 400VDC bus with robust OVP/UVLO and thermal-stable reference for downstream inverter stage. Use Value: −40°C to +85°C rating ensures reliability under ambient thermal cycling; VRMS feedforward maintains PF >0.99 across full input range without firmware tuning. |
| Medical Imaging Power Module | Telecom Rectifier Shelf |
Use Scenario: High-reliability 1.5kW X-ray generator power supply demanding low EMI, fast transient response, and fault-safe shutdown. IC Role / Device Role / Timing Role: Safety-critical PFC controller with dual OVP latching, soft-start controlled ramp, and precise 7.5V reference for stable bus regulation. Use Value: 400mV OVP hysteresis prevents nuisance tripping during load transients; ZVTOUT-driven snubbing suppresses conducted EMI below CISPR 11 limits. | Use Scenario: 48V telecom rectifier with hot-swap capability and strict hold-up time requirements under 200VAC nominal input. IC Role / Device Role / Timing Role: High-accuracy PFC controller delivering tightly regulated 380VDC bus with <±1% ripple and programmable soft-start timing. Use Value: 1% reference tolerance and 80dB voltage amplifier gain ensure <0.5% output regulation error; SS pin allows adjustable start-up slew rate for inrush control. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PFC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC3855BDW | Commercial temperature grade (0°C to +70°C); identical pinout, architecture, and electrical specs except UVLO (10.5V) and temp range. | Not rated for industrial ambient extremes; unsuitable for deployments exceeding 70°C case temperature or sub-zero startup. | Select UC2855BDW for systems requiring guaranteed operation at −40°C or continuous 85°C ambient. |
| L6562A | Single-channel average current-mode PFC controller without ZVT; 65kHz–250kHz range; no CI/CS synthesizer; uses shunt-based current sensing only. | Lacks resonant snubbing capability and current transformer synthesis-requires higher-loss shunt resistor and cannot achieve same EMI/efficiency at >300kHz. | Choose L6562A only if ZVT complexity is unnecessary and cost sensitivity outweighs efficiency/EMI targets. |
Compared with UC3855BDW, UC2855BDW adds industrial temperature qualification and tighter UVLO hysteresis, while L6562A offers lower-cost basic PFC control but omits ZVT, current synthesis, and high-frequency scalability-making UC2855BDW optimal for high-density, high-efficiency industrial PFC designs.
Availability
UC2855BDW is available at Aetrix Electronics and suitable for server power supplies, industrial motor drives, medical imaging equipment, and telecom rectifiers requiring stable component supply with long lifecycle visibility.
Supply support for UC2855BDW 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 ICs, with decades of expertise in power conversion and control architectures.
The UC2855BDW belongs to TI's legacy Unitrode PFC controller family, designed specifically for high-efficiency, high-power-factor AC-DC front-end regulation in industrial and computing power systems.
FAQ
What is the operating temperature range of the UC2855BDW?
The UC2855BDW is specified for industrial operation from −40°C to +85°C junction temperature. This range is validated per TI's characterization and qualifies the device for use in server PSUs, industrial motor drives, and telecom rectifiers exposed to extended ambient thermal stress. The UC2855BDW datasheet confirms this range explicitly for the "B" variant, distinguishing it from the commercial-grade UC3855BDW (0°C to +70°C). All electrical parameters in the datasheet's Electrical Characteristics table are guaranteed across this full range.
Does the UC2855BDW support zero-voltage switching (ZVS) for the main boost MOSFET?
The UC2855BDW does not directly sense or control ZVS of the main boost MOSFET. Instead, it implements Zero Voltage Transition (ZVT) via the ZVS input and ZVTOUT driver to control an auxiliary MOSFET that resonantly discharges the boost diode's stored charge before the main switch turns on. This indirect ZVT technique reduces diode recovery loss and main switch turn-on loss, enabling higher efficiency and lower EMI-but does not require direct drain-source voltage sensing on the primary switch. The UC2855BDW datasheet defines ZVTOUT as a dedicated 750mA peak driver for this auxiliary function.
Can the UC2855BDW operate without a current sense transformer?
Yes, the UC2855BDW supports resistive shunt-based current sensing as an alternative to transformer coupling. The CA and CS pins accept direct voltage signals from a shunt, though the current synthesizer circuitry (CI/ION path) is optimized for transformer input. When using a shunt, designers must bypass the ION buffer and connect the shunt voltage directly to CS, disabling the synthesizer's reconstruction function. The UC2855BDW datasheet states "Average current sensing can be employed using a simple resistive shunt or a current sense transformer," confirming dual-sensing flexibility-though transformer use delivers superior noise immunity and efficiency.
What is the purpose of the VRMS pin on the UC2855BDW?
On the UC2855BDW, the VRMS pin accepts a DC voltage proportional to the RMS value of the rectified AC input (typically 1.5V at low line, 4.7V at high line). This signal feeds the internal analog multiplier to scale the current command inversely with VRMS², ensuring constant power delivery and near-unity power factor across universal input ranges (90–264VAC). The VRMS input extends from 0 to 5.5V and enables faster line transient response than conventional feedforward methods. Its use is mandatory for automatic universal input operation and is explicitly required in all UC2855BDW reference designs.
How does the UC2855BDW handle overvoltage protection?
The UC2855BDW implements hardware-based overvoltage protection (OVP) via the OVP pin, which monitors the boost output through an external resistor divider. When the sensed voltage exceeds 7.66V (typical), the internal hysteretic comparator latches and disables both GTOUT and ZVTOUT outputs until the voltage decays by at least 400mV (hysteresis). This action is independent of the main control loop and occurs within 200ns propagation delay. The OVP function is fully self-contained-no external logic or microcontroller intervention is needed-and remains active even during UVLO or soft-start phases, ensuring fail-safe boost stage protection.
UC2855BDW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- 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:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
UC2855BDW FAQ
1.How can I place an order for UC2855BDW through Aetrix?
Please submit a Request for Quotation (RFQ) for UC2855BDW 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 UC2855BDW reliable?
The price and inventory of UC2855BDW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC2855BDW is usually 5 days.
3.What payment methods are accepted for UC2855BDW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC2855BDW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC2855BDW?
UC2855BDW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC2855BDW 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 UC2855BDW?
For technical support, including UC2855BDW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC2855BDW requirements.
6.How does Aetrix verify that UC2855BDW is sourced from the original manufacturer or authorized distributors?
All UC2855BDW 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 UC2855BDW meets industry standards.
7.What is the process for return or replacement of UC2855BDW?
All UC2855BDW units undergo pre-shipment inspection (PSI). If there is an issue with UC2855BDW, 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 UC2855BDW part is unused and in its original packaging.
Return procedure for UC2855BDW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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