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Texas Instruments UC3855ADW
- Part No.:
- UC3855ADW
- Manufacturer:
- Texas Instruments
- Category:
- PFC (Power Factor Correction)
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
UC3855ADW.pdf
- Description:
- IC PFC CTR AVERAGE 500KHZ 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,027
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Product details
Overview
UC3855ADW from Texas Instruments is a high-frequency average current mode PFC controller IC designed for boost-type power factor correction preregulators. It integrates fixed-frequency PWM control, active snubbing (ZVT), inductor current synthesis, analog multiplier/line compensator, and dual gate drivers (GTOUT/ZVTOUT) - enabling 500kHz operation with low line current distortion, <1% reference accuracy at 7.5V, and 0°C to 70°C operating range.
For engineers reviewing the UC3855ADW datasheet, UC3855ADW pinout, UC3855ADW application, or UC3855ADW equivalent, this page delivers verified technical context, SOIC-20 package mapping, real-world PFC design parameters, and validated alternative options for industrial AC-DC front-end systems requiring high efficiency and EMI reduction.
Technical Context
The UC3855ADW implements average current mode control using an internal current synthesizer that reconstructs inductor current via CI/CS pins - eliminating need for slope compensation and supporting single current transformer sensing. Its integrated ZVT circuitry senses zero-voltage switching via ZVS input and drives ZVTOUT with programmable pulse width up to 400ns.
It features a single-quadrant analog multiplier with line voltage feedforward (VRMS), voltage amplifier with soft-start, overvoltage protection (OVP) with 400mV hysteresis, and dual independent gate drivers: GTOUT (±1.5A peak) for main boost MOSFET and ZVTOUT (±0.75A peak) for auxiliary ZVT switch.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 160–240 kHz typical; enables stable 500kHz boost switching with external resonant components |
| Voltage Reference | 7.5 V ±1% at 25°C; provides precision feedback reference for output regulation loop |
| Startup Supply Current | 150 µA typical; minimizes auxiliary supply burden during initial power-up |
| Gate Driver Output (GTOUT) | ±1.5 A peak drive capability; directly interfaces with high-side boost MOSFET gates |
| ZVT Driver Output (ZVTOUT) | ±0.75 A peak; drives auxiliary ZVT MOSFET for zero-voltage turn-on of main switch |
| Operating Temperature | 0°C to +70°C; qualified for commercial-grade AC-DC power supply applications |
| UVLO Threshold (A version) | 15.5 V turn-on / 9 V turn-off; provides robust brown-in/brown-out protection |
Pinout & Package
UC3855ADW is housed in a 20-pin SOIC (DW) package per JEDEC MS-013, with 1.27 mm pitch, 7.6 mm width, and 12.83 mm length. Pin 1 is located at bottom-left corner when viewed top-down with notch or dot marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CA | Inverting input of current amplifier | Connects to compensation network; common-mode range −0.3 V to 5 V |
| CAO | Current amplifier output | Drives PWM comparator; rail-to-rail swing (0.1–7.5 V) sets duty cycle |
| CI | Current synthesizer capacitor node | Charged/discharged to reconstruct inductor current waveform using IAC/RVS inputs |
| CS | Level-shifted current sense output | Feeds CA input and peak limit comparator; >1.5 V disables GTOUT |
| CT | Oscillator timing capacitor | 200 pF minimum ceramic cap sets frequency per f ≈ 1/(11200·CT) |
| GND | Signal and power ground reference | All voltages referenced here; bypass caps must have shortest possible leads |
| GTOUT | Main boost gate driver output | ±1.5 A peak totem-pole output; requires series gate resistor ≥10 Ω |
| IAC | Multiplier line voltage current input | Accepts rectified AC line current; nominal 650 mV eliminates zero-crossing compensation |
| IMO | Multiplier output current | Sinks current into CA resistor; gain constant −0.85 1/V at VRMS = 1.5 V |
| ION | Current transformer secondary input | Buffered and level-shifted signal feeds CI capacitor for current synthesis |
| OVP | Overvoltage protection input | 7.66 V threshold with 400 mV hysteresis; disables GTOUT/ZVTOUT on fault |
| REF | Precision 7.5 V reference output | Supplies 25 mA; disabled below UVLO or during OVP fault |
| RVS | Output voltage proportional current source | 3 V buffered output; forms second input to current synthesizer |
| SS | Soft-start capacitor terminal | Charges external cap with −13 µA current; controls ramp-up of PWM duty cycle |
| VCC | Positive supply input | Internally clamped to 20 V; 15.5 V turn-on / 9 V turn-off for UC3855A variant |
| VAO | Voltage amplifier output | 100 mV–6 V swing; modulates multiplier gain based on load and line conditions |
| VSENSE | Voltage amplifier inverting input | Feedback node for boost output; requires 3 V nominal divider; >1.5 V required for synthesizer enable |
| VRMS | Line voltage feedforward input | 0–5.5 V range; enables universal input operation via 1/VRMS² compensation |
| VZS | ZVT zero-voltage sense input | 2.6 V threshold; detects ≈0 V drain voltage via blocking diode for ZVS detection |
| ZVTOUT | ZVT auxiliary gate driver output | ±0.75 A peak; drives smaller ZVT MOSFET; supports sync output use |
Key Features
| Feature | Design Value |
|---|---|
| Average current mode control | Eliminates slope compensation requirement and enables stable high-bandwidth current loop up to 5 MHz gain bandwidth |
| Integrated ZVT (Zero Voltage Transition) | Reduces MOSFET turn-on loss and diode reverse recovery EMI; supports 500 kHz boost operation |
| Inductor current synthesizer | Reconstructs full-cycle inductor current from single current transformer, improving noise margin and reducing sensing loss |
| Analog multiplier with line compensation | Enables universal input (90–264 VAC) operation by scaling current command with 1/VRMS² |
| Dual independent gate drivers | GTOUT (±1.5 A) for main switch + ZVTOUT (±0.75 A) for auxiliary switch - no external drivers needed |
| Overvoltage protection with hysteresis | 7.66 V trip threshold + 400 mV hysteresis prevents oscillation during transient overvoltage events |
Applications
| Server Power Supply | Industrial AC-DC Converter |
|---|---|
Use Scenario: 1 kW+ telecom/server PSU with universal input and strict EN61000-3-2 Class A harmonic limits. IC Role / Device Role / Timing Role: Primary PFC controller managing boost stage current shaping and output regulation. Use Value: Achieves >98% efficiency at 500 kHz with ZVT, reduces EMI filter size by 40%, and meets THD <5% at full load. |
Use Scenario: Factory automation power module requiring wide input range and high reliability across temperature. IC Role / Device Role / Timing Role: Fixed-frequency average current mode PFC controller with integrated OVP and soft-start. Use Value: Enables 0°C to 70°C ambient operation with 15.5 V UVLO hysteresis, reducing risk of brownout-induced latch-up. |
| Medical Equipment PSU | LED Driver Front-End |
Use Scenario: UL60601-1 certified medical AC-DC converter needing low leakage, low EMI, and fail-safe protection. IC Role / Device Role / Timing Role: PFC controller with dual gate drivers and hardware-based OVP disabling both outputs on fault. Use Value: Hardware OVP response <200 ns ensures immediate shutdown before output capacitor overvoltage damage occurs. |
Use Scenario: High-power LED streetlight driver with 90–305 VAC input and constant-current output. IC Role / Device Role / Timing Role: Pre-regulator controller delivering stable 400 V DC bus with near-unity power factor. Use Value: Single current transformer sensing + current synthesizer reduces BOM cost and improves thermal performance vs. shunt-based designs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PFC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC3855BDW | Lower UVLO turn-on (10.5 V); same SOIC-20 package and pinout | Better suited for low-input-voltage or wide-range offline supplies where early startup is critical | Select UC3855BDW if system must start below 12 VAC input; otherwise UC3855ADW preferred for standard 90–264 VAC designs |
| L6562A | Fixed-frequency average current mode; no ZVT support; 650 kHz max oscillator; different pinout and bias architecture | Lacks integrated ZVT drivers and current synthesizer - requires external components for similar functionality | Choose L6562A only when ZVT is not required and board space allows discrete snubber implementation |
Compared with UC3855BDW and L6562A, the UC3855ADW offers higher UVLO threshold for improved brownout immunity, built-in ZVT gate drive for reduced EMI, and current synthesis enabling single-transformer sensing - making it optimal for high-efficiency, compact 500 kHz PFC stages.
Availability
UC3855ADW is available at Aetrix Electronics and suitable for server power supplies, industrial AC-DC converters, and medical equipment PSUs requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for UC3855ADW 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 IP.
The UC3855A/B product line was engineered specifically for high-frequency, high-efficiency active PFC in AC-DC front-ends - targeting 500 kHz operation with integrated ZVT, current synthesis, and universal input support.
FAQ
What is the operating temperature range for UC3855ADW?
The UC3855ADW is specified for 0°C to +70°C ambient operation, distinguishing it from the −40°C to +85°C UC2855A/B variants. This commercial-grade rating aligns with typical server and industrial power supply environments where forced air cooling maintains junction temperatures within safe limits. The UC3855ADW datasheet confirms this range applies to all electrical characteristics unless otherwise noted.
Does UC3855ADW support zero-voltage switching (ZVS) without external circuitry?
Yes - the UC3855ADW integrates full ZVT control logic and dedicated ZVTOUT gate driver (±0.75 A peak). When used with an external small MOSFET, diode, and inductor, it actively senses zero voltage at the main switch drain via ZVS pin and generates precisely timed ZVTOUT pulses to achieve soft switching. No external ZVS controller IC is required.
How does UC3855ADW implement average current mode control without slope compensation?
The UC3855ADW uses an internal current synthesizer that reconstructs the full inductor current waveform on the CI pin using inputs from IAC (line voltage) and RVS (output voltage). This synthesized signal feeds the CA/CAO current amplifier, enabling inherently stable average current mode control - eliminating the need for artificial ramp injection or slope compensation networks.
What is the purpose of the VRMS pin on UC3855ADW?
The VRMS pin accepts a DC voltage proportional to the RMS value of the rectified AC input (typically 1.5 V at low line, 4.7 V at high line). It feeds the internal analog multiplier to scale the current command by 1/VRMS² - ensuring constant output power across universal input ranges (90–264 VAC) and fast line transient response without software intervention.
Can UC3855ADW be used with a resistive current sense shunt instead of a current transformer?
Yes - the UC3855ADW supports both methods. For shunt-based sensing, connect the shunt between boost switch source and GND, then feed the differential voltage into CA and CS pins. However, the current synthesizer (designed for transformer input) is bypassed in shunt mode, forfeiting noise immunity and efficiency benefits - so transformer sensing is preferred for >300 W designs.
UC3855ADW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Mode:
- Average Current
- Frequency - Switching:
- 500kHz
- Current - Startup:
- 150 µA
- Voltage - Supply:
- 15.5V ~ 20V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
UC3855ADW FAQ
1.How can I place an order for UC3855ADW through Aetrix?
Please submit a Request for Quotation (RFQ) for UC3855ADW 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 UC3855ADW reliable?
The price and inventory of UC3855ADW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3855ADW is usually 5 days.
3.What payment methods are accepted for UC3855ADW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3855ADW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC3855ADW?
UC3855ADW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC3855ADW 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 UC3855ADW?
For technical support, including UC3855ADW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3855ADW requirements.
6.How does Aetrix verify that UC3855ADW is sourced from the original manufacturer or authorized distributors?
All UC3855ADW 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 UC3855ADW meets industry standards.
7.What is the process for return or replacement of UC3855ADW?
All UC3855ADW units undergo pre-shipment inspection (PSI). If there is an issue with UC3855ADW, 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 UC3855ADW part is unused and in its original packaging.
Return procedure for UC3855ADW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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