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Texas Instruments UCC38502DWTR
- Part No.:
- UCC38502DWTR
- Manufacturer:
- Texas Instruments
- Category:
- PFC (Power Factor Correction)
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
UCC38502DWTR.pdf
- Description:
- IC PFC CTR AVERAGE 100KHZ 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,871
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Product details
Overview
UCC38502DWTR from Texas Instruments is a dual-stage active power factor correction (PFC) and DC-DC controller IC integrating average-current-mode PFC control with peak-current-mode downstream PWM control. It delivers near-unity power factor, programmable 100 kHz oscillator, 16 V/10 V UVLO threshold for bootstrap bias operation, and synchronized leading-edge (PFC) / trailing-edge (DC-DC) modulation to minimize bulk capacitor ripple in universal-input AC-DC supplies.
For engineers reviewing the UCC38502DWTR datasheet, UCC38502DWTR pinout, UCC38502DWTR application, or UCC38502DWTR equivalent, key selection criteria include its dual-stage control architecture, 7.5 V internal reference accuracy, 50% maximum duty cycle clamp on GT2, zero-power detection at 0.33 V on VAOUT, and compatibility with boost + forward topologies requiring coordinated soft-start and overvoltage protection.
Technical Context
The UCC38502DWTR implements a two-stage control architecture: the PFC stage uses average current-mode control with line voltage feedforward (VFF) derived from IAC mirroring and a single-pole external filter, while the second stage employs peak current-mode control with externally generated error signal fed via VERR. Its multiplier divides line current by VFF² to maintain constant input power across 85–265 VRMS inputs.
It features synchronized start-up sequencing-holding the DC-DC stage off until PFC output reaches regulation (±10%), then executing controlled soft-start via SS2 charge current of −10 µA. The PWM stage shuts down when PFC output falls below 50% of nominal due to its wide UVLO2 hysteresis (2.4–3.6 V), distinguishing it from UCC38500/501 variants.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Temp Range | 0°C to 70°C - specified for commercial-grade industrial power supplies with ambient thermal constraints |
| Oscillator Frequency | 80–120 kHz - programmable via RT/CT; initial accuracy ±15% at 25°C enables stable switching in universal-input designs |
| VREF Output | 7.5 V ±12 mV - high-accuracy internal reference used for PKLMT level-shifting and peripheral biasing |
| PFC UVLO Threshold | 16 V turn-on / 10 V turn-off - wide hysteresis supports self-biasing from bulk capacitor during startup |
| PWM UVLO2 Hysteresis | 2.4–3.6 V - enables robust second-stage shutdown at 50% bulk voltage, critical for low-line brownout recovery |
| GT1/GT2 Drive Capability | 1.2 A pulsed / 0.2 A continuous - sufficient to drive MOSFET gates directly without external buffers in ≤100 W systems |
| Zero-Power Detection | 0.175–0.5 V on VAOUT - disables outputs when PFC output collapses, preventing uncontrolled discharge into downstream stage |
Pinout & Package
UCC38502DWTR is housed in a 20-pin SOIC (DW) package with exposed thermal pad, optimized for surface-mount assembly and thermal dissipation in compact AC-DC adapters and industrial power supplies.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GT1 | PFC gate driver output | Drives boost switch with 93–100% max duty cycle; requires ≥10.5 Ω series gate resistor to limit overshoot |
| GT2 | DC-DC gate driver output | Trailing-edge modulated; clamped to ≤50% duty cycle to ensure transformer reset in forward converters |
| IAC | AC line current sensing input | Current-mode input (≤500 µA) feeding analog multiplier; enables RMS feedforward without high-voltage components |
| VFF | Feedforward voltage node | Generated by mirroring IAC; sets VFF = 1.4 V at low line to scale PFC gain and maintain constant input power |
| SS2 | Second-stage soft-start control | Charged at −10 µA; voltage ramps to enable controlled PWM duty-cycle ramp-up after PFC regulation is achieved |
| OVP/ENBL | Window comparator input | Disables PFC if boost output exceeds +6.67%; pulls low to disable both stages and reset SS2 during fault conditions |
Key Features
| Feature | Design Value |
|---|---|
| Integrated dual-stage control | Eliminates need for separate PFC and PWM controllers, reducing BOM count and layout complexity in 2-stage AC-DC supplies |
| Leading-edge PFC + trailing-edge PWM | Minimizes overlap conduction between boost and DC-DC switches, cutting bulk capacitor ripple current by up to 40% vs. unsynchronized schemes |
| Programmable oscillator | RT/CT configuration allows precise frequency tuning (80–120 kHz) to balance EMI, efficiency, and magnetics size |
| Line feedforward (VFF) | Derived from IAC mirroring + RC filter; replaces high-voltage resistive dividers, lowering cost and improving safety compliance |
| Synchronized soft-start | Internal sequencing ensures PFC reaches regulation before enabling DC-DC stage, preventing inrush stress on boost inductor and diode |
Applications
| Server Power Supply | Industrial Motor Drive PSU |
|---|---|
Use Scenario: 100-W universal-input AC-DC supply powering server management modules with strict hold-up time and THD requirements. IC Role / Device Role / Timing Role: UCC38502DWTR serves as primary controller for boost PFC + forward DC-DC stages, managing input current shaping, bulk voltage regulation, and isolated secondary-side error feedback via optocoupler to VERR. Use Value: Achieves >0.99 power factor and <5% THD across 85–265 VRMS, meeting EN61000-3-2 Class D; synchronized soft-start prevents bulk capacitor discharge into unregulated DC-DC stage. | Use Scenario: Compact 75-W auxiliary power supply for PLC I/O modules operating in harsh industrial environments with wide temperature and line-voltage variation. IC Role / Device Role / Timing Role: UCC38502DWTR controls continuous-conduction-mode boost PFC followed by non-isolated buck-derived DC-DC, using VFF feedforward to maintain regulation during 15% line sags. Use Value: Wide UVLO2 hysteresis (2.4–3.6 V) enables reliable restart after brownouts; zero-power detection at 0.33 V VAOUT prevents uncontrolled discharge during AC loss events. |
| Medical Diagnostic Equipment PSU | LED Driver Reference Design |
Use Scenario: Low-noise, low-EMI 65-W power supply for portable ultrasound imaging units requiring clean 12 V/5 A output and regulatory compliance. IC Role / Device Role / Timing Role: UCC38502DWTR implements leading-edge PFC and trailing-edge forward converter with opto-coupled VERR feedback, coordinating timing to suppress common-mode noise coupling into sensitive analog front-end circuits. Use Value: Trailing-edge modulation on GT2 reduces high-frequency switching noise; CAOUT's low-offset current amplifier (±6 mV) ensures accurate line-current sensing for tight THD control. | Use Scenario: High-efficiency 100-W constant-current LED driver for architectural lighting with dimming interface and surge immunity. IC Role / Device Role / Timing Role: UCC38502DWTR manages boost PFC stage and secondary-side synchronous rectified buck converter, using OVP/ENBL pin to implement overvoltage lockout during open-circuit LED faults. Use Value: Programmable PKLMT threshold (0 V reference) enables precise peak-current limiting for LED string current control; 50% GT2 duty-cycle clamp ensures safe operation with high-duty-cycle LED loads. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-stage PFC+PWM controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC28502DWTR | Rated for –40°C to 85°C; identical pinout and functional spec but wider temp range and narrower PFC UVLO hysteresis (1.2 V vs. 6.3 V) | Preferred for extended-temperature industrial or telecom equipment where ambient exceeds 70°C | Select UCC28502DWTR when operating beyond 0–70°C range; otherwise UCC38502DWTR offers tighter thermal budget control in commercial applications |
| ICE2PCS01 | Single-chip PFC+PWM controller with integrated 650 V MOSFET; no external gate drivers required; fixed 65 kHz frequency | Suitable for cost-sensitive, lower-power (<65 W) designs where integration outweighs programmability needs | Choose ICE2PCS01 for simplified layout and reduced component count in sub-65 W applications; UCC38502DWTR retains flexibility for higher-power or custom-frequency designs |
Compared with UCC28502DWTR, UCC38502DWTR trades extended temperature rating for tighter thermal margin control in commercial environments; versus ICE2PCS01, it provides full external gate drive, programmable frequency, and independent PFC/DC-DC optimization-critical for >80 W, high-efficiency, or EMI-sensitive designs.
Availability
UCC38502DWTR is available at Aetrix Electronics and suitable for server power supplies, industrial motor drive PSUs, medical diagnostic equipment PSUs, and LED driver reference designs requiring stable component supply and long-term production continuity.
Supply support for UCC38502DWTR 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 expertise in power conversion IC design.
The UCC3850x product line was engineered specifically for cost-effective, high-performance two-stage AC-DC power supplies targeting universal-input, regulated DC outputs in commercial and industrial equipment.
FAQ
What is the purpose of the VFF pin on the UCC38502DWTR?
The VFF pin on the UCC38502DWTR generates a feedforward voltage proportional to the RMS input line voltage by mirroring half the IAC current through an external RC filter. This signal scales the PFC multiplier gain to maintain constant input power across 85–265 VRMS inputs, eliminating high-voltage resistive dividers and improving efficiency and safety. At low line, VFF is 1.4 V; at high line, it reaches ~4.7 V. The UCC38502DWTR uses this to divide line current by VFF² in the analog multiplier.
How does the UCC38502DWTR handle start-up sequencing between the PFC and DC-DC stages?
The UCC38502DWTR internally coordinates start-up by monitoring the PFC output via VAOUT and holding the DC-DC stage disabled until VAOUT reaches within 10% of regulation. Once triggered, SS2 charges at −10 µA to ramp the PWM duty cycle gradually. If VAOUT drops below 50% of nominal (due to its wide UVLO2 hysteresis), the DC-DC stage shuts down-preventing overstress during brownouts. This sequencing is intrinsic to the UCC38502DWTR and requires no external logic.
What is the function of the OVP/ENBL pin on the UCC38502DWTR?
The OVP/ENBL pin on the UCC38502DWTR is a dual-function window comparator input. When voltage exceeds VREF + 0.5 V (≈8.0 V), it disables only the PFC gate driver (GT1) to prevent overvoltage on the bulk capacitor. When pulled below 1.9 V, it disables both GT1 and GT2 and resets SS2-effectively halting all switching and initiating a full restart. It also defines the active range for the second-stage PWM, making it central to fault response and system enable control in the UCC38502DWTR.
Can the UCC38502DWTR be used with a flyback DC-DC topology?
Yes, the UCC38502DWTR supports flyback topologies for the second stage, though it is optimized for forward converters. The VERR pin accepts externally generated error signals-typically from an optocoupler on the secondary side-enabling isolation. For flyback use, ensure the external error amplifier provides appropriate compensation and that the 50% GT2 duty-cycle clamp aligns with transformer reset requirements. Peak current sensing on ISENSE2 remains valid, and slope compensation can be added via CT ramp injection, as documented in the UCC38502DWTR datasheet.
What is the significance of the 50% maximum duty cycle on GT2 in the UCC38502DWTR?
The 50% maximum duty cycle enforced on GT2 in the UCC38502DWTR ensures safe transformer reset in forward and push-pull topologies by guaranteeing a minimum off-time for magnetic core demagnetization. This hard clamp prevents saturation under transient load or startup conditions. It is implemented via internal logic tied to the oscillator and cannot be overridden. Designers must size the transformer turns ratio and output rectifier accordingly-e.g., selecting a 1:1.2 step-down ratio to maintain regulation at 50% duty cycle under worst-case line and load conditions in the UCC38502DWTR.
UCC38502DWTR 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:
- 100kHz
- Current - Startup:
- 150 µA
- Voltage - Supply:
- 9.7V ~ 18V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
UCC38502DWTR FAQ
1.How can I place an order for UCC38502DWTR through Aetrix?
Please submit a Request for Quotation (RFQ) for UCC38502DWTR 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 UCC38502DWTR reliable?
The price and inventory of UCC38502DWTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UCC38502DWTR is usually 5 days.
3.What payment methods are accepted for UCC38502DWTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UCC38502DWTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UCC38502DWTR?
UCC38502DWTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UCC38502DWTR 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 UCC38502DWTR?
For technical support, including UCC38502DWTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UCC38502DWTR requirements.
6.How does Aetrix verify that UCC38502DWTR is sourced from the original manufacturer or authorized distributors?
All UCC38502DWTR 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 UCC38502DWTR meets industry standards.
7.What is the process for return or replacement of UCC38502DWTR?
All UCC38502DWTR units undergo pre-shipment inspection (PSI). If there is an issue with UCC38502DWTR, 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 UCC38502DWTR part is unused and in its original packaging.
Return procedure for UCC38502DWTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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