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Texas Instruments UC2854BQ
- Part No.:
- UC2854BQ
- Manufacturer:
- Texas Instruments
- Category:
- PFC (Power Factor Correction)
- Package:
- 20-LCC (J-Lead)
- Datasheet:
-
UC2854BQ.pdf
- Description:
- IC PFC CTR AVERAGE 120KHZ 20PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:3,050
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Product details
Overview
UC2854BQ from Texas Instruments is a high-power-factor preregulator IC implementing average current-mode control for boost-type active PFC stages. It integrates a 7.5-V precision voltage reference, analog multiplier/divider, voltage and current amplifiers, fixed-frequency PWM, and 1-A totem-pole gate driver. Designed for universal-input (75–275 VAC) offline AC/DC supplies, it achieves 0.99 power factor and <5% line-current distortion in medical, telecom, and industrial power systems.
For engineers reviewing the UC2854BQ datasheet, UC2854BQ pinout, UC2854BQ application, or UC2854BQ equivalent, key selection considerations include its 46–62 kHz programmable oscillator frequency, ±4 mV current amplifier offset, 70–100 dB voltage amplifier gain, 14.5-V max gate drive output, and –40°C to +85°C operating junction temperature range.
Technical Context
The UC2854BQ employs average current-mode control-eliminating slope compensation needs and delivering stable, low-distortion sinusoidal line current across continuous and discontinuous conduction modes. Its analog multiplier accepts IAC (line-voltage-derived current) and VRMS (RMS feedforward) inputs to generate a shaped current command at MULTOUT.
Internal functional blocks include a voltage error amplifier with soft-start via SS pin, a current error amplifier with ISENSE/MULTOUT differential input, a 55 kHz oscillator set by RSET and CT, and a clamped GTDRV output limiting gate voltage to 15 V. The device features 10.5-V VCC turn-on threshold and 0.5-V UVLO hysteresis-optimized for reliable startup under brownout conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator frequency | 46–62 kHz (set by RSET=15 kΩ & CT=1.5 nF; enables EMI-compliant switching in boost PFC) |
| Voltage reference output | 7.5 V ±0.15 V (stable, 10 mA capable reference for feedback and biasing; enables accurate loop scaling) |
| Current amplifier offset | ±4 mV (low offset ensures minimal DC error in sensed line current, critical for THD <5%) |
| Gate driver output voltage | 14.5 V max (internally clamped; safely drives N-channel MOSFET gates without external Zener) |
| VCC UVLO turn-on threshold | 10.5 V typical (enables robust startup from bulk capacitor discharge; lower than UC3854's 16 V) |
| Operating junction temperature | –40°C to +85°C (industrial-grade thermal rating; supports enclosed power supply environments) |
| Multiplier output current | –200 µA typical (IAC=100 µA, VRMS=1.25 V, VVAOUT=6 V; defines current-command magnitude for PFC loop) |
Pinout & Package
UC2854BQ is housed in a 16-pin SOIC package (7.50 mm × 10.30 mm body size) with standard JEDEC MS-012AC footprint and 1.27 mm pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Power and signal reference ground | Return path for VCC bypass, CT discharge, and all internal amplifiers; requires direct 0.1 µF ceramic bypass |
| PKLMT (Pin 2) | Peak current limit input | Threshold = 0 V; connects to negative side of sense resistor to enable cycle-by-cycle overcurrent shutdown |
| CAOUT (Pin 3) | Current amplifier output | Drives PWM comparator; swings to ~0.5 V above GND; remains active during disable for fast recovery |
| ISENSE (Pin 4) | Current-sense inverting input | Differential input with MULTOUT; accepts signals down to –0.3 V; must avoid < –0.5 V to prevent diode conduction |
| MULTOUT (Pin 5) | Multiplier output / current-sense non-inverting input | High-impedance current output; tied to CAOUT input; enables noise-rejecting differential current sensing |
| IAC (Pin 6) | AC line current input to multiplier | Current-mode input (nominal 6 V bias); senses rectified line voltage waveform for feedforward shaping |
| VAOUT (Pin 7) | Voltage amplifier output | Regulates boost output voltage; clamped to 5.8 V; drives multiplier and provides soft-start reference |
| VRMS (Pin 8) | RMS line voltage feedforward input | Accepts 1.5–3.5 V signal proportional to input RMS; compensates for line-voltage variations in real time |
| VREF (Pin 9) | Precision 7.5-V reference output | 10 mA capable; disabled when VCC < UVLO or ENA = low; requires 0.1 µF ceramic bypass to GND |
| ENA (Pin 10) | Enable logic input | Active-high (2.55 V threshold); enables oscillator, reference, and PWM; releases SS clamp on assertion |
| VSENSE (Pin 11) | Voltage amplifier inverting input | Connects to output voltage divider; sets regulated output level (e.g., 400 VDC); bias current < ±500 nA |
| RSET (Pin 12) | Oscillator charging current / multiplier limit set | Resistor to GND programs oscillator frequency and caps multiplier output current (IMULTOUT ≤ 3.75 V/RRSET) |
| SS (Pin 13) | Soft-start timing node | Internally sourced 14 mA current; ramps VAOUT reference slowly; discharges rapidly on fault or disable |
| CT (Pin 14) | Oscillator timing capacitor | Capacitor to GND sets ramp frequency; valley = 1.1 V, peak = 5.4 V; requires short, low-inductance GND path |
| VCC (Pin 15) | Positive supply input | 10–20 V operation; 16 mA typical supply current; must exceed 10.5 V to enable; bypassed directly to GND |
| GTDRV (Pin 16) | Gate driver output | Totem-pole MOSFET driver; 1-A peak; 35 ns rise/fall (1 nF load); clamped to 15 V; series gate resistor ≥5 Ω required |
Key Features
| Feature | Design Value |
|---|---|
| Average current-mode control | Enables stable, low-THD line current without slope compensation-critical for EN61000-3-2 Class D compliance |
| Feedforward line regulation via VRMS | Compensates for input voltage variation in real time, maintaining constant output power and minimizing transient response delay |
| Low-noise analog multiplier/divider | Uses IAC current input and VRMS feedforward to generate precise instantaneous current command-reducing harmonic distortion |
| Integrated 7.5-V precision reference | Stable, low-drift reference with 10 mA drive capability-eliminates need for external reference in most PFC designs |
| 1-A totem-pole gate driver with 15-V clamp | Directly drives power MOSFET gates without external level-shifting or clamping-reducing BOM count and layout complexity |
Applications
| Medical Power Supplies | Industrial AC/DC Converters |
|---|---|
|
Use Scenario: 250-W universal-input AC/DC front-end for diagnostic imaging equipment requiring >0.99 PF and <5% THD per IEC 60601-1. IC Role / Device Role / Timing Role: UC2854BQ serves as the active PFC controller, regulating boost stage current to match sinusoidal line voltage while maintaining 400 VDC output. Use Value: Achieves 0.999 PF and 3.81% THD at full load-meeting stringent medical EMC and efficiency requirements without external harmonic filters. |
Use Scenario: 500-W industrial PLC power module operating from 85–264 VAC with wide ambient temperature range (–40°C to +70°C). IC Role / Device Role / Timing Role: UC2854BQ implements fixed-frequency average current-mode control to ensure stable PFC across line and load transients. Use Value: –40°C to +85°C junction rating and 0.5-V UVLO hysteresis enable reliable cold-start and brownout recovery in factory-floor environments. |
| Telecom Rectifiers | UPS Input Stages |
|
Use Scenario: 1-kW telecom rectifier complying with NEBS Level 3 and GR-1089-CORE for conducted emissions. IC Role / Device Role / Timing Role: UC2854BQ controls the boost PFC stage, using VRMS feedforward and IAC sensing to minimize 3rd/5th harmonics. Use Value: Feedforward line regulation reduces output voltage deviation to <±1% during 10% line sags-maintaining downstream DC/DC stability. |
Use Scenario: Online UPS with bidirectional AC/DC conversion where input PFC must operate continuously during battery backup transitions. IC Role / Device Role / Timing Role: UC2854BQ manages boost converter current shaping while VAOUT remains active during brief ENA/VCC interruptions. Use Value: Voltage amplifier stays enabled during disable cycles-keeping large loop compensation capacitors charged for sub-100 µs recovery. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar active power factor correction applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC3854BDW | Higher VCC UVLO (16 V), wider temp range (0°C to 70°C), no internal VREF good circuitry | Designed for commercial-temp consumer/IT power; less suitable for industrial brownout-prone environments | Select UC2854BQ for industrial designs needing lower 10.5-V turn-on and –40°C operation |
| UCC28511D | Enhanced version with improved THD, integrated soft-start, and higher gate drive (1.5 A); 8-pin SOIC | Targets cost-sensitive, space-constrained designs; lacks VRMS feedforward and analog multiplier flexibility | Choose UC2854BQ when full analog multiplier control, feedforward, and design legacy compatibility are required |
Compared with UC3854BDW and UCC28511D, UC2854BQ offers the optimal balance of industrial temperature support, low-VCC startup, and full analog control architecture-making it preferred for ruggedized, high-fidelity PFC implementations where feedforward accuracy and THD minimization are critical.
Availability
UC2854BQ is available at Aetrix Electronics and suitable for medical power supplies, industrial AC/DC converters, and telecom rectifiers requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for UC2854BQ 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 delivering analog, embedded processing, and connectivity solutions with emphasis on reliability, precision, and energy efficiency.
The UC2854BQ belongs to TI's UCx854 family of high-power-factor preregulators-designed specifically for average current-mode active PFC in universal-input offline power supplies targeting EN61000-3-2 compliance.
FAQ
What is the operating temperature range of the UC2854BQ?
The UC2854BQ is rated for an operating junction temperature range of –40°C to +85°C. This industrial-grade specification allows deployment in demanding environments such as factory automation, outdoor telecom cabinets, and medical equipment enclosures where ambient temperatures fluctuate widely. The UC2854BQ's thermal metrics-including 71.5°C/W RθJA for the SOIC package-support reliable operation under continuous load when properly heatsinked and airflow-managed. Always verify PCB copper area and airflow against TI's thermal guidelines in SLUS336A.
How does the UC2854BQ achieve power factor correction?
The UC2854BQ achieves active power factor correction using average current-mode control. It multiplies a scaled representation of the instantaneous line voltage (via IAC input) with a feedforward signal proportional to line RMS voltage (VRMS) and the output voltage error (VAOUT), generating a precise sinusoidal current command at MULTOUT. This command is compared against the sensed inductor current (at ISENSE) in the current amplifier, and the resulting error drives a fixed-frequency PWM that controls the boost switch via GTDRV-forcing input current to track the line voltage waveform with <5% distortion.
What is the function of the VRMS pin on the UC2854BQ?
The VRMS pin on the UC2854BQ accepts a DC voltage (1.5–3.5 V) proportional to the RMS value of the AC input line voltage. Internally, this signal is squared and fed into the analog multiplier's divider path, enabling real-time compensation for line voltage variations. This feedforward action maintains constant output power and minimizes output voltage deviation during line sags or surges-reducing the burden on the voltage loop and improving dynamic response. Proper scaling of the VRMS network is essential to avoid multiplier saturation or loss of regulation.
Can the UC2854BQ be used in discontinuous conduction mode (DCM)?
Yes, the UC2854BQ supports both continuous and discontinuous conduction modes in boost PFC topologies. Its average current-mode architecture inherently maintains stable, low-distortion line current regardless of conduction mode-unlike peak current-mode controllers that require slope compensation in DCM. In DCM operation, the UC2854BQ's current amplifier continues to integrate the inductor current waveform over the full switching cycle, ensuring accurate average current regulation and consistent THD performance across light-load conditions where DCM naturally occurs.
What are the key differences between UC2854BQ and UC3854BDW?
The UC2854BQ features a lower VCC turn-on threshold (10.5 V vs. 16 V), tighter UVLO hysteresis (0.5 V vs. 6 V), and industrial temperature rating (–40°C to +85°C vs. 0°C to +70°C), making it more robust in brownout-prone and thermally demanding applications. The UC3854BDW offers higher current amplifier bandwidth (5 MHz vs. 400–800 kHz) and lacks internal VREF good circuitry. Both share identical pinout and core functionality, but UC2854BQ is optimized for reliability in harsh environments where UC3854BDW may fail to start or regulate.
UC2854BQ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 20-LCC (J-Lead)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Mode:
- Average Current
- Frequency - Switching:
- 80kHz ~ 120kHz
- Current - Startup:
- 250 µA
- Voltage - Supply:
- 10V ~ 20V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-PLCC (9x9)
UC2854BQ FAQ
1.How can I place an order for UC2854BQ through Aetrix?
Please submit a Request for Quotation (RFQ) for UC2854BQ 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 UC2854BQ reliable?
The price and inventory of UC2854BQ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC2854BQ is usually 5 days.
3.What payment methods are accepted for UC2854BQ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC2854BQ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC2854BQ?
UC2854BQ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC2854BQ 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 UC2854BQ?
For technical support, including UC2854BQ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC2854BQ requirements.
6.How does Aetrix verify that UC2854BQ is sourced from the original manufacturer or authorized distributors?
All UC2854BQ 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 UC2854BQ meets industry standards.
7.What is the process for return or replacement of UC2854BQ?
All UC2854BQ units undergo pre-shipment inspection (PSI). If there is an issue with UC2854BQ, 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 UC2854BQ part is unused and in its original packaging.
Return procedure for UC2854BQ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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