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Texas Instruments UC3854N/2
- Part No.:
- UC3854N/2
- Manufacturer:
- Texas Instruments
- Category:
- PFC (Power Factor Correction)
- Package:
- -
- Datasheet:
-
UC3854N/2.pdf
- Description:
- IC REG LINEAR PB REGULATOR SONY
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Product details
Overview
UC3854N/2 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 - enabling >0.99 power factor and <5% line-current distortion in offline AC–DC supplies operating from 75–275 VAC at 50–400 Hz.
For engineers reviewing the UC3854N/2 datasheet, UC3854N/2 pinout, UC3854N/2 application, or UC3854N/2 equivalent, key selection considerations include its 55 kHz typical oscillator frequency, 70–100 dB voltage amplifier gain, –4 to +4 mV current amplifier offset, 16-pin PDIP package with GND-referenced ISENSE/MULTOUT inputs, and compatibility with universal-input industrial/medical/telecom power supplies requiring EN61000-3-2 Class D compliance.
Technical Context
The UC3854N/2 employs average current-mode control - not peak mode - eliminating slope compensation while maintaining sinusoidal line current across continuous/discontinuous conduction transitions. Its analog multiplier accepts IAC (6 V nominal) and VRMS (1.5–3.5 V) inputs to generate a feedforward-modulated current command, while the voltage amplifier regulates output via VSENSE feedback with soft-start controlled by SS capacitor ramp.
Internal circuitry includes a 14-mA SS charge current source, 15-V clamped GTDRV output, 7.5-V VREF capable of sourcing 10 mA, and dual comparators for VCC UVLO (16 V turn-on, 10 V turn-off) and ENA enable (2.55 V threshold). The device operates over 0°C to 70°C junction temperature and supports stable operation with CT = 1.5 nF and RSET = 15 kΩ.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator frequency | 55 kHz typical (RSET = 15 kΩ, CT = 1.5 nF); sets fixed PWM switching rate for EMI control and inductor sizing. |
| Voltage reference | 7.5 V ±0.15 V over temperature; powers external bias networks and serves as soft-start and error amplifier reference. |
| Current amplifier offset | ±4 mV max; directly impacts line-current zero-crossing accuracy and THD performance at light load. |
| Gate driver output | 1-A peak, 15-V clamped; drives MOSFET gates without external level-shifting, supporting >200 kHz boost designs. |
| VCC UVLO threshold | 16 V turn-on / 10 V turn-off (6 V hysteresis); ensures reliable startup and brownout recovery in unregulated auxiliary supplies. |
| Input voltage range (VRMS) | 1.5–3.5 V; enables feedforward line-voltage compensation to maintain constant output power across universal AC input. |
| Supply current (ON) | 10–16 mA; determines minimum auxiliary supply capability required for sustained operation. |
Pinout & Package
UC3854N/2 is housed in a 16-pin plastic dual in-line package (PDIP), 6.35 mm × 19.30 mm body size, with through-hole mounting and standard 0.3-inch lead spacing. Pin 1 is bottom-left corner when notch faces up.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1) | Power and signal reference | Common return for VCC, VREF bypass, CT discharge, and all internal amplifiers; requires direct 0.1-µF ceramic connection. |
| PKLMT (Pin 2) | Peak current limit input | Zero-threshold comparator input tied to current-sense resistor negative terminal; triggers immediate PWM shutdown on overcurrent. |
| CAOUT (Pin 3) | Current amplifier output | Emitter-follower output driving PWM comparator; swings to near-GND to force zero duty cycle during fault or soft-start. |
| ISENSE (Pin 4) | Current-sense inverting input | Differential input referenced to MULTOUT; accepts negative-going signals down to –0.3 V, enabling ground-referenced shunt sensing. |
| MULTOUT (Pin 5) | Multiplier output / CA+ input | High-impedance current output connected to CA non-inverting input; forms differential pair with ISENSE for noise-immune current sensing. |
| IAC (Pin 6) | AC line voltage feedforward input | 6-V biased current input proportional to rectified line voltage; cancels crossover distortion when resistor-ratio matched to VREF. |
| VAOUT (Pin 7) | Voltage amplifier output | Open-collector-like emitter-follower output (0.5–5.8 V swing); provides loop compensation node and feeds multiplier for feedforward control. |
| VRMS (Pin 8) | RMS line voltage input | 1.5–3.5 V input scaling line voltage magnitude; enables input-voltage-dependent current command to maintain constant output power. |
| VREF (Pin 9) | 7.5-V reference output | Stable, short-circuit protected reference for external circuits and internal soft-start clamp; disabled when ENA = low or VCC < UVLO. |
| ENA (Pin 10) | Enable logic input | Active-high TTL/CMOS input (2.55 V threshold); enables oscillator, VREF, and PWM; releases SS clamp to initiate soft-start ramp. |
| VSENSE (Pin 11) | Voltage feedback inverting input | High-impedance input for resistive divider from boost output; sets regulated DC bus voltage (e.g., 400 VDC) via error amplifier comparison to VREF. |
| RSET (Pin 12) | Oscillator & multiplier limit set | Resistor-to-GND programs oscillator charging current and maximum multiplier output current (IMULTOUT ≤ 3.75 V / RRSET). |
| SS (Pin 13) | Soft-start timing node | Internally charged to >8 V at 14 mA; controls voltage amplifier reference during startup to limit inrush current and prevent output overshoot. |
| CT (Pin 14) | Oscillator timing capacitor | Capacitor-to-GND sets PWM frequency; CT ramp amplitude (4.9–5.9 V) drives PWM comparator against CAOUT. |
| VCC (Pin 15) | Positive supply input | 10–20 V operating range; must deliver ≥20 mA; bypassed directly to GND to support GTDRV gate-charge transients. |
| GTDRV (Pin 16) | Gate drive output | Totem-pole MOSFET driver (1-A peak); 15-V internal clamp prevents gate overvoltage; requires ≥5 Ω series resistor for stability. |
Key Features
| Feature | Design Value |
|---|---|
| Average current-mode control | Enables stable, low-distortion sinusoidal line current without slope compensation across CCM/DCM transitions. |
| Feedforward line regulation | VRMS and IAC inputs jointly scale current command to maintain constant output power over 75–275 VAC input range. |
| Integrated 7.5-V reference | 10-mA capable, ±0.15-V tolerance over temperature; eliminates need for external reference in most PFC designs. |
| 1-A totem-pole gate driver | Directly drives boost MOSFET gates up to 1-A peak; 15-V clamp protects against VCC overvoltage during transient conditions. |
| Low-noise analog multiplier | Accepts IAC current and VRMS voltage inputs to generate precise line-synchronized current command with <5% THD. |
Applications
| Industrial AC–DC Power Supplies | Medical Equipment Power |
|---|---|
Use Scenario: 250-W universal-input front-end for programmable logic controller (PLC) power module operating from 85–264 VAC. IC Role / Device Role / Timing Role: UC3854N/2 acts as the active PFC controller, regulating boost stage to draw near-sinusoidal current and maintain 400 VDC bus under varying load and line conditions. Use Value: Achieves 0.999 PF and 3.81% THD per EN61000-3-2 Class D, enabling compliance without passive filtering or derating. | Use Scenario: Isolated 300-W power supply for diagnostic imaging equipment requiring ultra-low EMI and high reliability. IC Role / Device Role / Timing Role: UC3854N/2 implements feedforward-controlled average current-mode PFC to stabilize input current waveform despite rapid load transients from X-ray pulsing. Use Value: Maintains <5% line-current distortion across 0–100% load and 50–60 Hz line frequency, reducing conducted emissions into sensitive analog front-ends. |
| Telecom Rectifier Systems | Uninterruptible Power Supplies (UPS) |
Use Scenario: 1-kW telecom rectifier operating from 100–240 VAC with hot-swap redundancy and -48 VDC output. IC Role / Device Role / Timing Role: UC3854N/2 controls the first-stage boost converter to deliver regulated 380 VDC bus, feeding downstream isolated DC–DC converters. Use Value: Enables world-wide operation without manual voltage switches while meeting IEC 61000-3-2 harmonic limits up to 400 Hz line frequency. | Use Scenario: Online double-conversion UPS with battery backup, requiring high-efficiency AC–DC conversion and fast dynamic response. IC Role / Device Role / Timing Role: UC3854N/2 manages input PFC stage during normal operation and maintains regulated bus during brief AC dropouts via hold-up capacitor support. Use Value: Soft-start (SS pin) and undervoltage lockout (VCC UVLO) ensure graceful entry/exit from battery mode without bus collapse or inrush stress. |
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 |
|---|---|---|---|
| UC3854BDWTR | SOIC-16 surface-mount package; 5-MHz current amplifier bandwidth vs. UC3854N/2's 1-MHz; 10.5-V VCC turn-on threshold. | Designed for higher-frequency, lower-THD designs where layout parasitics demand faster current-loop response. | Select UC3854BDWTR for new SMT designs targeting <3% THD at full load; UC3854N/2 remains optimal for cost-sensitive through-hole industrial supplies. |
| UCC3854N | Same PDIP-16 package; improved VREF line regulation (±2 mV vs. ±10 mV); enhanced ESD rating (±3000 V HBM). | Better suited for high-reliability environments with noisy auxiliary supplies or handling-sensitive assembly lines. | Choose UCC3854N when long-term supply continuity and robustness outweigh minor cost premium over UC3854N/2. |
Compared with UC3854BDWTR and UCC3854N, the UC3854N/2 offers proven thermal performance in PDIP packaging, simpler layout for through-hole manufacturing, and sufficient bandwidth for 50–60 Hz line applications - making it ideal for legacy industrial and medical power supplies where design stability and component longevity are prioritized.
Availability
UC3854N/2 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-life obsolescence management, and traceable sourcing from authorized channels.
Supply support for UC3854N/2 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 for industrial, automotive, and communications markets.
The UC3854N/2 belongs to TI's legacy UCx854 active PFC controller family, designed specifically for high-efficiency, high-power-factor offline power supplies targeting EN61000-3-2 compliance in industrial, medical, and telecom infrastructure.
FAQ
What is the operating temperature range for the UC3854N/2?
The UC3854N/2 is rated for 0°C to 70°C junction temperature, as specified in the Recommended Operating Conditions table. This range aligns with commercial-grade applications such as industrial power supplies and telecom rectifiers. Operation outside this range may cause parameter drift or functional failure; thermal design must ensure junction temperature remains within limits under worst-case load and ambient conditions. The UC3854N/2 datasheet confirms this range applies specifically to the N-suffix (PDIP) variant.
How does the UC3854N/2 achieve power factor correction without slope compensation?
The UC3854N/2 uses average current-mode control instead of peak current-mode, eliminating the need for slope compensation. Its current amplifier compares the average sensed line current (via ISENSE and MULTOUT) to a sinusoidal command derived from the analog multiplier, ensuring accurate current tracking across continuous and discontinuous conduction modes. This architecture inherently rejects noise transients and maintains <5% line-current distortion without external compensation components - a core differentiator confirmed in the UC3854N/2 datasheet's Functional Description section.
Can the UC3854N/2 be used with a 400-Hz aircraft power input?
Yes, the UC3854N/2 supports line frequencies from 50 Hz to 400 Hz, as explicitly stated in the device description and recommended operating conditions. Its feedforward architecture (VRMS and IAC inputs) and average current-loop bandwidth (1-MHz current amplifier) maintain stable PFC performance across this full range. Designers must verify CT and RSET values meet oscillator frequency requirements and that input filter components are rated for 400-Hz operation - both validated in TI's UC3854N/2 application notes for aerospace use cases.
What is the purpose of the PKLMT pin on the UC3854N/2?
The PKLMT (Pin 2) on the UC3854N/2 is a peak current limit input with a 0-V threshold. It connects directly to the negative side of the current-sense resistor and triggers immediate PWM shutdown when pulled slightly below ground - providing cycle-by-cycle overcurrent protection for the boost switch. This function operates independently of the average current loop and remains active even during soft-start or disable states, ensuring robust fault coverage. The UC3854N/2 datasheet specifies PKLMT offset voltage as ±10 mV, confirming its precision for fast, reliable limiting.
Does the UC3854N/2 require an external oscillator component?
No, the UC3854N/2 contains an internal fixed-frequency oscillator requiring only an external timing capacitor (CT) connected to Pin 14 and GND. A resistor from RSET (Pin 12) to GND sets the oscillator charging current and thus determines frequency - e.g., 55 kHz with RSET = 15 kΩ and CT = 1.5 nF. No external resistor or crystal is needed. This integrated oscillator architecture simplifies design and improves noise immunity compared to externally clocked controllers, as documented in the UC3854N/2 Electrical Characteristics and Oscillator sections.
UC3854N/2 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Mode:
- -
- Frequency - Switching:
- -
- Current - Startup:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
UC3854N/2 FAQ
1.How can I place an order for UC3854N/2 through Aetrix?
Please submit a Request for Quotation (RFQ) for UC3854N/2 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 UC3854N/2 reliable?
The price and inventory of UC3854N/2 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3854N/2 is usually 5 days.
3.What payment methods are accepted for UC3854N/2?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3854N/2 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC3854N/2?
UC3854N/2 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC3854N/2 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 UC3854N/2?
For technical support, including UC3854N/2 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3854N/2 requirements.
6.How does Aetrix verify that UC3854N/2 is sourced from the original manufacturer or authorized distributors?
All UC3854N/2 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 UC3854N/2 meets industry standards.
7.What is the process for return or replacement of UC3854N/2?
All UC3854N/2 units undergo pre-shipment inspection (PSI). If there is an issue with UC3854N/2, 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 UC3854N/2 part is unused and in its original packaging.
Return procedure for UC3854N/2:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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