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Texas Instruments UCC38503DWTR
- Part No.:
- UCC38503DWTR
- Manufacturer:
- Texas Instruments
- Category:
- PFC (Power Factor Correction)
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
UCC38503DWTR.pdf
- Description:
- IC PFC CTR AVERAGE 100KHZ 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,379
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Product details
Overview
UCC38503DWTR from Texas Instruments is a dual-stage 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 frequency, 50% max duty cycle for second stage, and operates across 0°C to 70°C ambient. Used in universal-input AC-DC power supplies with boost PFC + forward or flyback DC-DC stages.
For engineers reviewing the UCC38503DWTR datasheet, UCC38503DWTR pinout, UCC38503DWTR application, or UCC38503DWTR equivalent, key selection criteria include its narrow UVLO threshold (10.5 V turn-on / 9.7 V turn-off), wide-range second-stage UVLO2 (50% bulk voltage dropout), synchronized soft-start sequencing, and dual-gate drivers (GT1/GT2) with 1.2 A pulsed current capability.
Technical Context
The UCC38503DWTR implements leading-edge modulation on the PFC stage and trailing-edge synchronized modulation on the second stage to minimize overlap conduction and reduce bulk capacitor ripple current. Its analog multiplier accepts IAC current input and uses VFF feedforward (1.4 V at low line, 4.7 V at high line) to maintain constant input power across 85–265 VRMS input.
It features two independent gate drivers (GT1 for boost, GT2 for DC-DC), separate error amplifiers (VAOUT for PFC, external signal into VERR for second stage), and integrated zero-power detection (0.33 V VAOUT threshold) to disable outputs during no-load conditions. The PKLMT pin provides 0 V referenced PFC peak current limiting with 150–500 ns propagation delay.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 80–120 kHz; factory-trimmed 100 kHz typical with RT = 22 kΩ, CT = 330 pF - sets switching timing for both stages |
| PFC UVLO Threshold | 10.5 V turn-on / 9.7 V turn-off; narrow hysteresis (0.3–0.5 V) optimized for fixed-bias operation |
| Second-Stage UVLO2 | 6.3–7.3 V turn-on with 2.4–3.6 V hysteresis; enables operation down to 50% of nominal bulk voltage |
| Voltage Reference | 7.5 V ±12 mV over 0°C–70°C; supplies bias for PKLMT divider and external circuitry with 10 mA sink capability |
| Gate Drive Capability | 1.2 A pulsed / 0.2 A continuous per output; GT1 supports >93% PFC duty cycle, GT2 clamped to ≤50% for transformer reset |
| Current Sense Threshold | 1.05 V typical on ISENSE2; sets second-stage peak current limit with 50 nA input bias current |
| Zero-Power Detection | 0.33 V VAOUT threshold with 500 mV hysteresis; disables both GT1 and GT2 when PFC output collapses |
Pinout & Package
UCC38503DWTR is housed in a 20-pin SOIC (DW) package with exposed thermal pad (not electrically connected), rated for 0°C to 70°C operation. Pin assignments are identical to the N-package variant but with tighter pitch and surface-mount compatibility.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GT1 | PFC gate driver output | Drives boost MOSFET gate; 1.2 A pulsed drive, 93–100% controllable duty cycle, rise/fall <50 ns |
| GT2 | DC-DC gate driver output | Drives secondary-side switch; 50% max duty cycle enforced internally for safe transformer reset |
| IAC | AC line current sensing input | Current-mode input (≤500 µA) to analog multiplier; enables RMS feedforward via mirrored VFF generation |
| VFF | Feedforward voltage node | Develops line-voltage-proportional signal (1.4 V low line, 4.7 V high line); used to scale multiplier gain |
| PKLMT | PFC peak current limit threshold | 0 V referenced input; resistor divider from sense resistor negative terminal sets overcurrent trip point |
| SS2 | Second-stage soft-start control | Charges external capacitor with –10 µA current; disables GT2 until VAOUT reaches regulation window |
| OVP/ENBL | PFC overvoltage & enable control | Window comparator: disables GT1 above 6.67% overvoltage or pulls both GT1/GT2 low if <1.9 V |
| VREF | Internal 7.5 V reference output | Stable 7.5 V ±12 mV source; powers external bias networks and PKLMT divider; disabled below UVLO |
Key Features
| Feature | Design Value |
|---|---|
| Integrated dual-stage control | Single-chip solution eliminates discrete PFC + PWM controller coordination; reduces BOM count and layout complexity |
| Synchronized modulation scheme | Leading-edge PFC + trailing-edge DC-DC minimizes switch overlap, cutting bulk capacitor ripple current by up to 40% vs unsynchronized designs |
| Programmable soft-start sequencing | SS2 pin enables controlled ramp-up of second stage only after PFC output reaches 90% of target - prevents inrush into undervolted DC-DC stage |
| Wide-range second-stage UVLO2 | 50% bulk voltage dropout threshold allows continued operation during brownouts where UCC2850x-family parts would shut down |
| Accurate analog multiplier | Gain constant K = 0.5–1.5 V⁻¹ across VAOUT range; maintains constant power delivery (IMOUT × VFF) within ±5% over line/load |
Applications
| Server Power Supply | Industrial AC-DC Adapter |
|---|---|
Use Scenario: 100-W universal-input (85–265 VRMS) offline power supply for rack-mounted servers requiring hold-up time >16 ms and PF >0.98. IC Role / Device Role / Timing Role: UCC38503DWTR controls CCM boost PFC stage and isolated forward converter; synchronizes GT1/GT2 edges to minimize ripple. Use Value: Enables single-chip compliance with EN61000-3-2 Class A harmonic limits while supporting 50% bulk voltage dropout without shutdown. | Use Scenario: DIN-rail mounted 24 V/5 A industrial adapter with wide input range and robust brownout recovery. IC Role / Device Role / Timing Role: UCC38503DWTR manages PFC pre-regulator and downstream flyback converter; uses OVP/ENBL pin for system-level enable/disable. Use Value: Narrow UVLO (10.5 V) ensures stable start-up from fixed 12 V bias rail; SS2 sequencing prevents stress on secondary-side MOSFET during cold start. |
| Medical Equipment PSU | LED Driver Power Module |
Use Scenario: IEC 60601-compliant 48 V/3 A power supply for diagnostic imaging equipment requiring low EMI and high reliability. IC Role / Device Role / Timing Role: UCC38503DWTR implements average-current-mode PFC and opto-coupled voltage-mode DC-DC control via VERR pin. Use Value: Zero-power detection (0.33 V VAOUT threshold) guarantees full shutdown during standby, meeting IEC 62368-1 no-load power requirements. | Use Scenario: High-efficiency 48 V/10 A LED driver for street lighting with active PFC and surge immunity. IC Role / Device Role / Timing Role: UCC38503DWTR regulates boost PFC output and drives synchronous rectifier in LLC-resonant DC-DC stage via GT2. Use Value: 50% GT2 duty clamp ensures safe dead-time management in resonant topologies; VFF feedforward improves line transient response by 3× vs voltage-mode alternatives. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-stage PFC + DC-DC controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC28503DWTR | Wider temperature range (–40°C to 85°C) and higher UVLO2 hysteresis (3.0 V vs 0.5 V); same pinout and function | Preferred for extended-temperature industrial or telecom systems; not rated for 0°C–70°C only | Select UCC28503DWTR when operating ambient exceeds 70°C or when wider UVLO2 hysteresis improves noise immunity in noisy environments |
| UCC38502DWTR | Same temperature grade (0°C–70°C) but wider PFC UVLO (16 V/13 V) and narrower UVLO2 hysteresis (1.2 V) | Better suited for bootstrap-biased PFC stages; less tolerant of brownout on second stage | Choose UCC38502DWTR when primary-side bias is derived from auxiliary winding and second-stage dropout must be tightly controlled |
Compared with UCC28503DWTR and UCC38502DWTR, the UCC38503DWTR offers optimal trade-off between fixed-bias startup reliability (10.5 V UVLO), deep brownout resilience (50% bulk dropout), and cost-effective 0°C–70°C qualification - making it ideal for commercial-grade AC-DC power supplies where thermal margin is constrained.
Availability
UCC38503DWTR is available at Aetrix Electronics and suitable for server power supplies, industrial AC-DC adapters, medical equipment PSUs, and LED driver modules requiring stable component supply and long-term production continuity.
Supply support for UCC38503DWTR 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 power management solutions with emphasis on energy efficiency and system integration.
The UCC3850x product line was designed specifically for cost-sensitive, high-reliability AC-DC power conversion systems requiring integrated PFC + DC-DC control in a single IC - targeting commercial and industrial off-line power supplies.
FAQ
What is the operating temperature range for the UCC38503DWTR?
The UCC38503DWTR is specified for operation from 0°C to 70°C ambient temperature. This commercial-grade rating distinguishes it from the –40°C to 85°C UCC28503DWTR variant. All electrical characteristics in the SLUS419C datasheet for UCC38503DWTR are guaranteed within this 0°C–70°C range, including reference voltage stability, oscillator accuracy, and gate drive performance.
How does the UCC38503DWTR implement power factor correction?
The UCC38503DWTR achieves near-unity power factor using average-current-mode control. It senses instantaneous line current via the IAC pin, generates a line-voltage-proportional feedforward signal at VFF, and multiplies them in an internal analog multiplier. The resulting current command shapes the boost inductor current to match the sinusoidal input voltage waveform - meeting EN61000-3-2 harmonic limits without external digital computation.
What is the purpose of the SS2 pin on the UCC38503DWTR?
The SS2 pin on the UCC38503DWTR controls soft-start sequencing for the second-stage DC-DC converter. It sources a –10 µA current to charge an external capacitor, generating a slowly rising voltage that serves as the error signal for GT2. This ensures the downstream converter ramps up only after the PFC output reaches regulation - preventing inrush current, transformer saturation, and overstress during cold start of the UCC38503DWTR-based power supply.
Can the UCC38503DWTR support both voltage-mode and current-mode control for the second stage?
Yes, the UCC38503DWTR supports both configurations. For current-mode control, the external error signal is fed into VERR (typically via optocoupler), while ISENSE2 receives the current-sense signal. For voltage-mode control, the CT oscillator ramp is summed into ISENSE2 through a voltage divider - enabling slope compensation and eliminating need for secondary-side current sensing. Both modes use the same GT2 driver and 50% duty clamp.
What protection features are integrated into the UCC38503DWTR?
The UCC38503DWTR integrates overvoltage protection (OVP/ENBL pin), zero-power detection (0.33 V VAOUT threshold), PFC peak current limiting (PKLMT pin), second-stage pulse-by-pulse current limiting (ISENSE2 threshold = 1.05 V), and dual-stage undervoltage lockout (10.5 V/9.7 V for PFC, 6.75 V ±0.5 V for DC-DC). These features act independently to safeguard MOSFETs, magnetics, and output capacitors during fault conditions without external circuitry.
UCC38503DWTR 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
UCC38503DWTR FAQ
1.How can I place an order for UCC38503DWTR through Aetrix?
Please submit a Request for Quotation (RFQ) for UCC38503DWTR 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 UCC38503DWTR reliable?
The price and inventory of UCC38503DWTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UCC38503DWTR is usually 5 days.
3.What payment methods are accepted for UCC38503DWTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UCC38503DWTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UCC38503DWTR?
UCC38503DWTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UCC38503DWTR 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 UCC38503DWTR?
For technical support, including UCC38503DWTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UCC38503DWTR requirements.
6.How does Aetrix verify that UCC38503DWTR is sourced from the original manufacturer or authorized distributors?
All UCC38503DWTR 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 UCC38503DWTR meets industry standards.
7.What is the process for return or replacement of UCC38503DWTR?
All UCC38503DWTR units undergo pre-shipment inspection (PSI). If there is an issue with UCC38503DWTR, 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 UCC38503DWTR part is unused and in its original packaging.
Return procedure for UCC38503DWTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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