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Texas Instruments UC3854Q
- Part No.:
- UC3854Q
- Manufacturer:
- Texas Instruments
- Category:
- PFC (Power Factor Correction)
- Package:
- 20-LCC (J-Lead)
- Datasheet:
-
UC3854Q.pdf
- Description:
- IC PFC CTR AVERAGE 200KHZ 20PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:3,567
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Product details
Overview
UC3854Q 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 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), 50–400 Hz offline AC/DC supplies delivering up to 400 VDC output.
For engineers reviewing the UC3854Q datasheet, UC3854Q pinout, UC3854Q application, or UC3854Q equivalent, key selection considerations include its 55 kHz typical oscillator frequency, 7.5 V reference accuracy (±0.2 V), 1-A gate drive capability, average current-mode stability without slope compensation, and compatibility with 16-pin SOIC packaging for industrial power supply designs.
Technical Context
The UC3854Q employs average current-mode control-using MULTOUT as current-sense+ and ISENSE as current-sense−-to enforce sinusoidal line current without slope compensation. Its analog multiplier accepts IAC (6 V nominal current input) and VRMS (1.5–3.5 V RMS feedforward) to generate a shaped current command proportional to line voltage squared.
Internal functional blocks include a voltage amplifier (100 dB gain, 5.8 V output swing) referenced to VREF or soft-start (SS), a current amplifier (1 MHz bandwidth, ±4 mV offset), and a clamped GTDRV output (15 V max, 35 ns rise/fall). The device operates across 0°C to 70°C junction temperature with VCC turn-on at 16 V and UVLO hysteresis of 6 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator frequency | 55 kHz typical (RSET = 15 kΩ); sets fixed PWM switching frequency for EMI control and inductor sizing. |
| Voltage reference (VREF) | 7.5 V ±0.15 V over temperature; powers external circuitry and serves as stable reference for VSENSE and SS. |
| Gate driver (GTDRV) | 1-A peak sink/source, 15 V clamped output; directly drives MOSFET gates without external level-shifting in boost preregulators. |
| Current amplifier BW | 1 MHz typical; enables fast response to line-current transients while maintaining low THD (<5%) under varying load. |
| Input voltage range (VRMS) | 1.5–3.5 V; accepts RMS-scaled line voltage for feedforward line regulation, improving dynamic response to input changes. |
| Operating temperature | 0°C to 70°C junction; qualified for commercial-industrial power supply environments, not extended automotive or military. |
| Supply current (ON) | 10–16 mA; low quiescent draw supports efficient operation in high-voltage auxiliary supplies. |
Pinout & Package
UC3854Q is packaged in a 16-pin SOIC (7.50 mm × 10.30 mm) with standard DW footprint. Pin functions are validated per TI SLUS336A Rev. December 2016.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Power and signal reference ground | Return path for CT timing discharge, VCC/VREF bypass, and all internal amplifiers; requires short, low-inductance connection to PCB ground plane. |
| PKLMT (Pin 2) | Peak current limit threshold | Zero-volt comparator input tied to current-sense resistor negative side; triggers immediate PWM shutdown if pulled below GND by >10 mV. |
| CAOUT (Pin 3) | Current amplifier output | Emitter-follower output driving PWM comparator; swings to near-GND to force zero duty cycle during fault or startup. |
| ISENSE (Pin 4) | Current-sense inverting input | Differential input to current amplifier; accepts negative-going voltage from sense resistor; must stay ≥ –0.5 V to avoid diode conduction. |
| MULTOUT (Pin 5) | Multiplier output / current-sense non-inverting input | High-impedance node connecting multiplier output to CA+; forms differential pair with ISENSE to reject ground noise in high-noise boost stages. |
| IAC (Pin 6) | AC current input to multiplier | 6 V-biased current input scaled from rectified line; primary waveform shaping input for sinusoidal current reference generation. |
| VAOUT (Pin 7) | Voltage amplifier output | Regulated error amplifier output (0.5–5.8 V); feeds multiplier and remains active during ENA disable to maintain loop charge state. |
| VRMS (Pin 8) | RMS line voltage feedforward | 1.5–3.5 V input scaling line voltage magnitude; compensates for input variations before they affect output regulation, reducing transient overshoot. |
| VREF (Pin 9) | 7.5 V precision reference output | Stable 10 mA-capable reference for feedback dividers, SS ramp, and peripheral biasing; disabled when VCC < 10 V or ENA = low. |
| ENA (Pin 10) | Enable logic input | Active-high TTL/CMOS input (2.55 V threshold); releases SS clamp and enables oscillator/VREF/GTDRV; not intended for high-speed PWM shutdown. |
| VSENSE (Pin 11) | Voltage amplifier inverting input | Feedback node for output voltage regulation; connected via resistive divider from 400 VDC boost output; bias current < 500 nA minimizes divider error. |
| RSET (Pin 12) | Oscillator charging & multiplier limit set | Resistor-to-GND sets oscillator frequency and caps multiplier output current (IMULTOUT ≤ 3.75 V / RRSET). |
| SS (Pin 13) | Soft-start timing capacitor | Internally sourced 14 mA current charges external capacitor; ramps VAOUT reference slowly to prevent inrush and output overshoot. |
| CT (Pin 14) | Oscillator timing capacitor | Capacitor-to-GND sets oscillator frequency (f ≈ 1.25 / RRSETCCT); requires low-ESR ceramic and shortest possible GND trace. |
| VCC (Pin 15) | Positive supply input | 10–20 V operating range; must deliver >20 mA; bypassed with ≥0.1 µF ceramic directly to GND to support GTDRV gate-charge spikes. |
| GTDRV (Pin 16) | Gate driver output | Totem-pole MOSFET driver (1 A peak); internally clamped to 15 V; requires ≥5 Ω series gate resistor to damp ringing on capacitive loads. |
Key Features
| Feature | Design Value |
|---|---|
| Average current-mode control | Enables stable, low-distortion (THD <5%) line current shaping across CCM/DCM transitions without slope compensation. |
| Feedforward line regulation (VRMS) | Reduces output voltage deviation during AC line sags/swells by pre-adjusting current reference before error amplifier correction. | 7.5 V precision reference (VREF) | ±0.15 V tolerance over 0°C–70°C enables accurate voltage feedback scaling and eliminates need for external reference in most PFC designs. |
| 1-A totem-pole gate driver (GTDRV) | Directly switches medium-power MOSFETs in boost stage without external drivers, reducing BOM count and layout complexity. |
| Low-noise analog multiplier/divider | Accepts IAC current and VRMS voltage inputs to generate precise, distortion-minimized current command proportional to vline². |
| Soft-start with SS pin | Programmable ramp time prevents inrush current and output overshoot by gradually increasing PWM duty cycle during startup. |
Applications
| Industrial AC/DC Power Supplies | Medical Equipment Power Modules |
|---|---|
Use Scenario: 250-W universal-input (85–264 VAC) offline power supply for programmable logic controllers (PLCs) requiring EN61000-3-2 Class D compliance. IC Role / Device Role / Timing Role: UC3854Q acts as the active PFC controller in the front-end boost stage, enforcing near-unity power factor and limiting line-current THD to 3.81% at full load. Use Value: Enables compliance with harmonic emission standards while supporting wide input range and stable 400 VDC bus generation for downstream DC/DC converters. | Use Scenario: Isolated 400 VDC intermediate bus generator for diagnostic imaging systems where EMI and reliability are critical. IC Role / Device Role / Timing Role: UC3854Q implements fixed-frequency (55 kHz) average current-mode control to minimize conducted EMI and ensure clean, regulated high-voltage rail for X-ray generator inverters. Use Value: Delivers 0.999 measured power factor and low noise sensitivity-critical for sensitive analog signal chains in medical instrumentation. |
| Telecom Rectifier Systems | Uninterruptible Power Supplies (UPS) |
Use Scenario: 1 kW telecom rectifier module operating from 48 VDC backup or 230 VAC mains, requiring high efficiency and low THD. IC Role / Device Role / Timing Role: UC3854Q controls the boost PFC stage to maintain constant 400 VDC output regardless of input source, using VRMS feedforward for rapid line regulation. Use Value: Supports seamless switchover between AC and DC inputs while sustaining EN61000-3-2 compliance and minimizing thermal stress on downstream converters. | Use Scenario: Online double-conversion UPS with battery backup, where input-stage PFC must operate continuously during utility and battery modes. IC Role / Device Role / Timing Role: UC3854Q provides continuous PFC control with ENA pin enabling/disabling based on input source status, while VAOUT remains charged during brief outages. Use Value: Maintains regulated 400 VDC bus during AC dropout events, allowing uninterrupted inverter operation and extending hold-up time without additional bulk capacitance. |
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 |
|---|---|---|---|
| UCC3854D | Same pinout and core architecture; improved 5-MHz current amplifier bandwidth vs UC3854Q's 1-MHz; lower VCC UVLO (10.5 V) and tighter multiplier gain (–0.9 to –1.1). | Better suited for high-bandwidth, low-THD designs requiring faster current-loop response; not drop-in due to different UVLO and reference behavior. | Select UCC3854D only if higher current-loop bandwidth and tighter multiplier tolerance are required-and board-level validation confirms stable operation with revised UVLO thresholds. |
| ICE3PCS01G | Fixed-frequency CCM PFC controller with integrated 650 V MOSFET; no external gate driver needed; uses digital multiplier and different pinout; lacks VRMS feedforward. | Targeted at cost-sensitive, lower-power (<300 W) consumer/IT supplies; eliminates external MOSFET but sacrifices design flexibility and feedforward line regulation. | Choose ICE3PCS01G for simplified, lower-BOM-cost designs where VRMS feedforward and discrete MOSFET selection are unnecessary. |
Compared with UC3854Q, UCC3854D offers higher current-loop bandwidth and tighter multiplier gain but requires revalidation of UVLO and soft-start behavior, while ICE3PCS01G integrates power switching at the expense of configurability and feedforward control-making UC3854Q optimal for flexible, high-performance industrial PFC stages.
Availability
UC3854Q is available at Aetrix Electronics and suitable for industrial AC/DC power supplies, medical equipment power modules, and telecom rectifier systems requiring stable component supply, long-lifecycle support, and verified PFC performance.
Supply support for UC3854Q 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 UC3854Q belongs to TI's legacy UCx854 family of high-power-factor preregulator controllers, designed specifically for average current-mode boost PFC in universal-input offline power supplies targeting EN61000-3-2 compliance.
FAQ
What is the recommended oscillator frequency setting for UC3854Q in a 250-W industrial PFC design?
The UC3854Q achieves a typical oscillator frequency of 55 kHz with RSET = 15 kΩ and CT = 1.5 nF, which balances EMI filtering requirements, inductor size, and MOSFET switching losses in 250-W industrial PFC stages. This value is confirmed in TI's SLUS336A datasheet Section 7.5 and aligns with typical application circuits achieving <5% THD. Adjusting RSET allows tuning between 46–62 kHz for specific layout or thermal constraints, but 55 kHz remains the validated baseline for UC3854Q.
How does the UC3854Q implement feedforward line regulation, and what is the valid input range for VRMS?
The UC3854Q implements feedforward line regulation via the VRMS pin, which accepts a voltage proportional to the RMS input line voltage and scales the analog multiplier's output to maintain constant output power across input variations. The valid VRMS input range is strictly 1.5 V to 3.5 V per Section 6 and 7.5 of the UC3854Q datasheet; operation outside this range degrades regulation accuracy and may cause instability. A resistor divider from rectified line voltage-calibrated to deliver 2.5 V at nominal 230 VAC-is commonly used.
Can UC3854Q be used in discontinuous conduction mode (DCM) boost PFC topologies?
Yes, the UC3854Q supports both continuous and discontinuous conduction mode (DCM) boost PFC operation without performance degradation, thanks to its average current-mode control architecture. Unlike peak current-mode controllers, UC3854Q maintains sinusoidal line current and low THD in DCM without slope compensation-verified in TI's application note and typical characteristics (Figure 3, SLUS336A). However, DCM operation requires careful selection of inductor value and RSET/CT to maintain stable 55 kHz switching.
What is the maximum gate drive current and voltage clamping behavior of UC3854Q's GTDRV pin?
The UC3854Q's GTDRV pin delivers up to 1 A peak sink/source current and is internally clamped to 15 V maximum, enabling direct drive of medium-power MOSFETs without external level-shifting. Under 200-mA load, GTDRV outputs 12.8 V high and 2.2 V low; with zero load, it reaches 14.5 V. The 15 V clamp protects MOSFET gates from overvoltage when VCC exceeds 20 V, and a minimum 5 Ω series gate resistor is required to suppress ringing on capacitive loads per TI's layout guidelines.
Does UC3854Q include built-in overvoltage or overtemperature protection?
No, the UC3854Q does not integrate overvoltage or overtemperature protection circuitry. It includes only overcurrent protection via the PKLMT pin and undervoltage lockout (UVLO) on VCC (16 V turn-on, 10 V turn-off). Output overvoltage must be handled externally-typically using a Zener clamp or optocoupler feedback to VSENSE-and thermal protection requires external circuitry (e.g., NTC thermistor into ENA or PKLMT). This is explicitly stated in the "Features" and "Description" sections of the UC3854Q datasheet (SLUS336A).
UC3854Q 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:
- 200kHz
- Current - Startup:
- 1.5 mA
- Voltage - Supply:
- 14.5V ~ 30V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-PLCC (9x9)
UC3854Q FAQ
1.How can I place an order for UC3854Q through Aetrix?
Please submit a Request for Quotation (RFQ) for UC3854Q 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 UC3854Q reliable?
The price and inventory of UC3854Q are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3854Q is usually 5 days.
3.What payment methods are accepted for UC3854Q?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3854Q transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC3854Q?
UC3854Q orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC3854Q 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 UC3854Q?
For technical support, including UC3854Q datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3854Q requirements.
6.How does Aetrix verify that UC3854Q is sourced from the original manufacturer or authorized distributors?
All UC3854Q 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 UC3854Q meets industry standards.
7.What is the process for return or replacement of UC3854Q?
All UC3854Q units undergo pre-shipment inspection (PSI). If there is an issue with UC3854Q, 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 UC3854Q part is unused and in its original packaging.
Return procedure for UC3854Q:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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