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Texas Instruments UCC28521DWR
- Part No.:
- UCC28521DWR
- Manufacturer:
- Texas Instruments
- Category:
- PFC (Power Factor Correction)
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
UCC28521DWR.pdf
- Description:
- IC PFC CTR AVERAGE 200KHZ 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,126
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Product details
Overview
UCC28521DWR from Texas Instruments is a dual-stage PFC/PWM combination controller IC for off-line AC-DC power supplies, implementing trailing-edge modulation for both stages, average-current-mode PFC control with input voltage feedforward, and peak-current-mode PWM control with programmable 70–80% maximum duty cycle clamp. It delivers 2-A source / 3-A sink gate drive on GT1 and GT2, supports IEC 1000−3−2 harmonic compliance, and targets high-efficiency server/desktop and telecom AC-DC converters.
For engineers reviewing the UCC28521DWR datasheet, UCC28521DWR pinout, UCC28521DWR application, or UCC28521DWR equivalent, key selection considerations include its 1:1 PFC:PWM frequency ratio, UVLO turn-on at 10.2 V with 0.5-V hysteresis, 200-kHz typical PWM frequency, 7.5-V precision reference, and PWM stage shutdown at 71% of nominal bulk voltage-critical for main DC-DC converter sequencing.
Technical Context
The UCC28521DWR integrates two independent control loops: a PFC section using a three-input linearized multiplier (IAC × VFF × VAOUT) with transconductance voltage amplifier and zero-power detect, and a PWM section featuring peak-current-mode operation with slope-compensation support via CT_BUFF, programmable soft-start via SS2, and internal 1.5-V level shift on ISENSE2 for noise immunity. Both stages share a common oscillator programmed by RT and operate synchronously at identical frequencies.
Startup sequencing is hardware-enforced: the PWM stage remains disabled until VAOUT reaches 90% of regulation, and during line dropout, GT2 shuts down when the PFC output falls to 71% of nominal bulk voltage-distinguishing it from UCC28528DW. The device uses separate analog (GND) and power (PWRGND) grounds, with Kelvin connection recommended between them to minimize ground bounce in high-current gate-drive paths.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| PFC:PWM Frequency Ratio | 1:1 - ensures synchronous timing alignment between boost PFC and downstream flyback/LLC PWM stages, simplifying EMI filter design and reducing beat-frequency artifacts. |
| PWM Max Duty Cycle Clamp | 75% typical - limits GT2 conduction time to prevent transformer saturation and ensure safe operation under high-line, low-load conditions. |
| UVLO Turn-On Threshold | 10.2 V ±0.5 V - guarantees reliable startup only after sufficient VCC rail stability, preventing erratic gate drive during brown-out recovery. |
| Gate Drive Strength | 2-A source / 3-A sink on GT1 & GT2 - directly drives MOSFET gates up to ~1.5 nF without external buffers, supporting fast switching in high-frequency PFC designs. |
| Reference Voltage | 7.5 V ±15 mV - provides stable bias for internal comparators and external feedback networks, with ≤5 mV load regulation up to 6 mA. |
| Zero Power Detect Threshold | 0.33 V on VAOUT - disables GT1 when system load drops below standby threshold, enabling true zero-power mode for energy-efficient offline supplies. |
| PWM Soft-Start Duration | Programmable via SS2 capacitor - controls ramp rate of VERR to limit inrush current and prevent overshoot during cold start of isolated DC-DC stage. |
Pinout & Package
UCC28521DWR is housed in a 20-pin SOIC (DW) package with exposed thermal pad, rated for operation from −40°C to +105°C and offering 84.3°C/W junction-to-ambient thermal resistance on low-K PCB.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GT1 (12) | PFC Gate Driver Output | 2-A source / 3-A sink totem-pole driver for boost switch; disabled outside UVLO window and before VREF stabilization. |
| GT2 (10) | PWM Gate Driver Output | Identical drive strength to GT1; PWM stage enabled only after PFC output reaches 90% regulation and disabled at 71% bulk voltage. |
| VSENSE (3) | PFC Voltage Feedback Input | Inverting input to transconductance amplifier; connects to output divider; enables OVP, enable, and UVLO2 functions. |
| VAOUT (1) | PFC Voltage Amplifier Output | Transconductance output regulating PFC bus; sources/sinks up to 30 µA linearly, up to 3.3 mA during slew enhancement; triggers zero-power shutdown below 0.33 V. |
| IAC (18) | Line Voltage Sensing Input | Current input proportional to rectified AC line; max 500 µA; feeds multiplier for input voltage feedforward and harmonic shaping. |
| VFF (19) | Voltage Feedforward Input | Sources IAC/2 current; external RC filter generates feedforward signal to multiplier-critical for near-unity power factor across universal input range. |
| RT (2) | Oscillator Programming Input | Resistor-to-GND sets CT_BUFF ramp frequency (65–600 kHz); determines both PFC and PWM switching frequency in UCC28521DWR. |
| D_MAX (4) | PWM Duty Cycle Clamp Input | DC voltage (0.09–0.90 ratio) sets maximum GT2 duty cycle; typically resistor-divided from VREF for precise 75% clamping. |
| SS2 (13) | PWM Soft-Start Input | Capacitor-to-GND programs soft-start duration; internal 10.5-µA current charges SS2 to 3 V, ramping VERR and GT2 duty cycle linearly. |
| ISENSE2 (8) | PWM Current Sense Input | Peak-current-mode input with 1.5-V internal level shift; 1.3-V threshold enables robust noise immunity in isolated feedback topologies. |
Key Features
| Feature | Design Value |
|---|---|
| Average-current-mode PFC control | Enables continuous conduction mode (CCM) operation with low THD and near-unity power factor across universal AC input (85–265 VAC). |
| Trailing-edge PFC/PWM modulation | Eliminates subharmonic oscillation risk in CCM PFC and simplifies synchronization with downstream isolated converters. |
| Integrated sequencing logic | Hardware-enforced startup (PFC first) and shutdown (PWM off at 71% bulk) prevent bus collapse and ensure stable cascade operation. |
| High-current dual gate drivers | 2-A/3-A GT1/GT2 outputs eliminate need for external driver stages, reducing BOM count and layout complexity in high-density PSU designs. |
| Input voltage feedforward | Compensates for line-voltage variation in real time via VFF path, maintaining constant power delivery and improving transient response to line steps. |
Applications
| Server Power Supply | Telecom AC-DC Converter |
|---|---|
Use Scenario: 80 PLUS Titanium-certified 1.5 kW redundant power supply for data center rack servers. IC Role / Device Role / Timing Role: UCC28521DWR controls interleaved boost PFC front-end and phase-shifted full-bridge PWM stage, enforcing IEC 61000-3-2 Class A harmonic limits. Use Value: 1:1 PFC:PWM synchronization reduces EMI filter size by 30%, while zero-power detect cuts no-load consumption to <0.5 W. | Use Scenario: -48 VDC telecom rectifier with universal AC input and hold-up time >20 ms. IC Role / Device Role / Timing Role: UCC28521DWR manages single-stage boost PFC and forward-converter PWM, with UVLO hysteresis ensuring reliable restart after grid sags. Use Value: Programmable D_MAX clamp prevents transformer saturation during high-line, light-load conditions-critical for telecom reliability standards. |
| Desktop PC Power Supply | Industrial AC-DC Module |
Use Scenario: ATX v2.4 compliant 750 W PSU with active PFC and LLC resonant secondary. IC Role / Device Role / Timing Role: UCC28521DWR governs boost PFC and primary-side PWM controller, coordinating gate timing to minimize cross-conduction losses. Use Value: 200-kHz typical switching frequency enables smaller magnetics and faster transient response to CPU load steps. | Use Scenario: DIN-rail mounted 48 V/20 A industrial power module for factory automation controllers. IC Role / Device Role / Timing Role: UCC28521DWR implements ruggedized PFC+PWM control with extended temperature rating (−40°C to +105°C) and reinforced isolation support. Use Value: Dual ground pins (GND + PWRGND) and Kelvin connection requirement reduce ground-loop noise in EMC-sensitive industrial environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PFC/PWM controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC28528DWR | PWM stage remains active until VCC drops below UVLO threshold; no 71% bulk shutdown logic. | Designed for auxiliary/standby supplies where continuous PWM operation during PFC bus decay is required. | Select UCC28528DWR only if main DC-DC must remain operational during brief AC line dips-UCC28521DWR is preferred for primary power conversion. |
| ICE3PCS01G | Fixed 65 kHz PFC frequency; no programmable RT oscillator; integrated 600 V startup circuit; no separate PWM gate driver. | Targeted at cost-sensitive consumer SMPS; lacks dual-stage independent control and high-current gate drive. | ICE3PCS01G suits entry-level designs needing basic PFC only; UCC28521DWR is required for synchronized PFC+PWM with full programmability and robust drive. |
Compared with UCC28528DWR and ICE3PCS01G, the UCC28521DWR uniquely combines programmable 1:1 synchronized PFC/PWM control, high-current dual gate drivers, and hardware-enforced sequencing-making it the only choice for high-efficiency, high-reliability main power conversion where bus stability and harmonic compliance are non-negotiable.
Availability
UCC28521DWR is available at Aetrix Electronics and suitable for high-efficiency server/desktop power supplies, telecom AC-DC converters, and industrial AC-DC modules requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for UCC28521DWR 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 over 50 years of power conversion innovation.
The UCC285xx family was designed specifically for high-performance, single-chip PFC+PWM control in off-line AC-DC systems targeting IEC 61000-3-2 compliance, efficiency optimization, and reduced system footprint.
FAQ
What is the primary function of the UCC28521DWR in an AC-DC power supply?
The UCC28521DWR serves as a dual-stage controller that simultaneously manages the power factor correction (PFC) boost stage and the downstream PWM DC-DC conversion stage within a single IC. It implements average-current-mode control for the PFC section and peak-current-mode control for the PWM section, with hardware-enforced startup sequencing and synchronized trailing-edge modulation-enabling compact, high-efficiency, and IEC 61000-3-2-compliant power supplies. Its architecture eliminates the need for separate PFC and PWM controllers.
How does the UCC28521DWR handle startup and shutdown sequencing between PFC and PWM stages?
The UCC28521DWR enforces strict hardware-based sequencing: the PWM stage (GT2) remains disabled until the PFC output voltage reaches 90% of its regulated value, ensuring stable bus voltage before secondary-stage activation. During line dropout or shutdown, the PWM stage turns off when the PFC output drops to 71% of nominal bulk voltage-preventing uncontrolled operation during bus decay. This behavior is intrinsic to the UCC28521DWR and differs from UCC28528DWR, which maintains PWM operation until VCC UVLO.
What is the role of the VFF pin on the UCC28521DWR, and how is it implemented externally?
The VFF (voltage feedforward) pin on the UCC28521DWR sources a current equal to half the IAC input current, enabling generation of a feedforward signal for the internal analog multiplier. Externally, a single-pole RC filter (resistor + capacitor to GND) is connected to VFF to produce a voltage proportional to the square of the rectified line voltage. At low line (e.g., 85 VAC), VFF is set to 1.4 V; at high line (265 VAC), it reaches ~4.7 V-ensuring constant power delivery and improved line-transient response in the UCC28521DWR.
Can the UCC28521DWR be used in a design requiring variable PFC and PWM frequencies?
No-the UCC28521DWR fixes both PFC and PWM frequencies to the same value, determined solely by the RT resistor. The oscillator frequency measured at CT_BUFF sets both stages' switching frequency, with a 1:1 ratio enforced internally. While RT allows adjustment across 65–600 kHz, independent frequency programming for PFC and PWM is not supported. For asymmetric frequency requirements, discrete PFC and PWM controllers or newer TI devices like UCC28070 would be necessary instead of the UCC28521DWR.
What thermal considerations apply to the UCC28521DWR in high-power applications?
The UCC28521DWR in DW package has a junction-to-ambient thermal resistance of 84.3°C/W on low-K PCB with LFM airflow. At full load, its power dissipation (up to 1.5 W at TA < 25°C) requires careful thermal layout: direct thermal pad soldering to copper pour, short low-impedance GND/PWRGND connections, and placement away from hot components. Derating begins at 84.3 mW/°C above 25°C, limiting usable power to 0.5 W at 105°C ambient-making heatsinking or forced air essential for sustained >500 W designs using the UCC28521DWR.
UCC28521DWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Mode:
- Average Current
- Frequency - Switching:
- 200kHz
- Current - Startup:
- 100 µA
- Voltage - Supply:
- 9.7V ~ 18V
- Operating Temperature:
- -40°C ~ 105°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
UCC28521DWR FAQ
1.How can I place an order for UCC28521DWR through Aetrix?
Please submit a Request for Quotation (RFQ) for UCC28521DWR 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 UCC28521DWR reliable?
The price and inventory of UCC28521DWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UCC28521DWR is usually 5 days.
3.What payment methods are accepted for UCC28521DWR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UCC28521DWR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UCC28521DWR?
UCC28521DWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UCC28521DWR 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 UCC28521DWR?
For technical support, including UCC28521DWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UCC28521DWR requirements.
6.How does Aetrix verify that UCC28521DWR is sourced from the original manufacturer or authorized distributors?
All UCC28521DWR 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 UCC28521DWR meets industry standards.
7.What is the process for return or replacement of UCC28521DWR?
All UCC28521DWR units undergo pre-shipment inspection (PSI). If there is an issue with UCC28521DWR, 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 UCC28521DWR part is unused and in its original packaging.
Return procedure for UCC28521DWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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