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Texas Instruments UCC3818AD
- Part No.:
- UCC3818AD
- Manufacturer:
- Texas Instruments
- Category:
- PFC (Power Factor Correction)
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
UCC3818AD.pdf
- Description:
- IC PFC CTR AVERAGE 220KHZ 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,357
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Product details
Overview
UCC3818AD from Texas Instruments is a BiCMOS average current-mode power factor correction (PFC) controller for boost preregulators, operating from 12 V to 18 V VCC, featuring 10.2 V UVLO turn-on threshold, 7.5 V reference output, and ±1.2 A peak gate drive capability. It enables near-unity power factor in IEC61000-3-2-compliant sub-300 W AC/DC supplies such as PC power supplies and industrial LED drivers.
For engineers reviewing the UCC3818AD datasheet, UCC3818AD pinout, UCC3818AD application, or UCC3818AD equivalent, key selection criteria include its 10.2 V/9.7 V UVLO hysteresis, 7.5 V precision reference, average current mode control architecture, soft-start functionality, and compatibility with fixed-VCC supply topologies.
Technical Context
The UCC3818AD implements average current mode control using a high-gain current amplifier (90 dB open-loop gain, ±2 mV offset), a voltage error amplifier (7.5 V reference input, 50–90 dB gain), and an analog multiplier with feed-forward (VFF) input for line regulation. Its oscillator supports 6 kHz–220 kHz via RT/CT programming, and leading-edge PWM modulation reduces bulk capacitor ripple.
It integrates overvoltage protection (OVP/EN pin with 1.07% reference and 500 mV hysteresis), zero-power detection (0.33 V threshold on VAOUT), and peak current limiting (PKLMT pin referenced to GND). The device operates across 0°C to 70°C and requires no external shunt regulator-designed specifically for fixed-VCC applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Operating Range | 12 V to 18 V - powers internal circuitry and gate driver without external biasing |
| UVLO Turn-On Threshold | 10.2 V (typ) - ensures reliable startup only after stable supply is established |
| VREF Output | 7.5 V ±1.5% - provides precision reference for voltage sensing and compensation networks |
| Gate Drive Capability | ±1.2 A peak - directly drives MOSFET gates with low Rpullup (9 Ω) and Rpulldown (4 Ω) |
| Oscillator Frequency Range | 6 kHz to 220 kHz - programmable via RT resistor and CT capacitor for EMI optimization |
| Current Amplifier Offset | ±2 mV (max) - minimizes light-load current waveform distortion in PFC stage |
| Soft-Start Charge Current | –10 µA (typ) - controls ramp rate of SS pin to limit inrush during startup |
Pinout & Package
UCC3818AD is housed in a 16-pin SOIC (D) package measuring 4.90 mm × 3.91 mm, with standard JEDEC MS-012AC footprint and gull-wing leads.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 GND | Ground reference | Common return path for all analog and power circuits; bypass VCC and VREF directly here |
| 2 PKLMT | Peak current limit input | Senses negative-side current sense resistor voltage; triggers shutdown when < 0 V |
| 3 CAOUT | Current amplifier output | Drives PWM latch; connects to MOUT for compensation network placement |
| 4 CAI | Current amplifier noninverting input | Connects to GND side of current sense resistor; functional down to below GND |
| 5 MOUT | Multiplier output / current amp inverting input | High-impedance node for differential current sensing and noise-immune leading-edge modulation |
| 6 IAC | Line voltage proportional current input | Accepts up to 500 µA current representing rectified AC line; enables feed-forward regulation |
| 7 VAOUT | Voltage amplifier output | Regulates boost output voltage; clamped at ~5.5 V to prevent overshoot |
| 8 VFF | Feed-forward voltage input | Receives RMS-scaled line voltage (1.4 V at low line); improves line regulation and THD |
| 9 VREF | 7.5 V reference output | Supplies 20 mA max; disabled below UVLO; bypass with ≥0.1 µF ceramic capacitor |
| 10 OVP/EN | Overvoltage/enable input | Window comparator: disables DRVOUT above programmed OVP level or below 1.9 V |
| 11 SSENSE | Voltage amplifier inverting input | Connects to output voltage divider; sets regulated output voltage via feedback ratio |
| 12 RT | Oscillator timing current input | Programs charging current (1.36–10 mA); nominal voltage = 3 V; use 10–100 kΩ resistor |
| 13 SS | Soft-start control | Charges external capacitor with –10 µA current; ramps duty cycle linearly during startup |
| 14 CT | Oscillator timing capacitor | With RT, sets switching frequency; short, direct GND trace required for stability |
| 15 VCC | Positive supply input | Requires ≥20 mA supply; bypassed to GND with ≥0.1 µF ceramic capacitor |
| 16 DRVOUT | Gate driver output | Totem-pole MOSFET driver; series gate resistor recommended to damp ringing |
Key Features
| Feature | Design Value |
|---|---|
| Average current mode control | Maintains stable, low-distortion sinusoidal line current without slope compensation |
| Leading-edge PWM modulation | Reduces ripple current in bulk output capacitor, extending electrolytic capacitor lifetime |
| Fixed-VCC optimized architecture | No internal shunt regulator-designed for dedicated 12–18 V supply, reducing external component count |
| Improved noise immunity | Differential current sensing (CAI/MOUT) and high CMRR current amplifier suppress EMI-induced errors |
| Accurate 7.5 V reference | ±1.5% tolerance over temperature enables precise voltage loop calibration and stable regulation |
| Zero-power detection | Shuts down gate drive when VAOUT falls below 0.33 V-prevents operation under no-load or fault conditions |
Applications
| PC Power Supply | Industrial LED Driver |
|---|---|
Use Scenario: 250 W ATX-compatible power supply meeting IEC61000-3-2 Class D limits. IC Role / Device Role / Timing Role: Primary PFC controller regulating boost stage to shape input current waveform matching AC line voltage. Use Value: Achieves >0.99 power factor at full load and <5% THD, enabling compliance without bulky passive filters. |
Use Scenario: Constant-power LED driver for high-bay lighting with universal 90–265 VAC input. IC Role / Device Role / Timing Role: Active PFC front-end preceding isolated DC-DC stage, ensuring stable bus voltage under wide input range. Use Value: Enables 92% system efficiency at 230 VAC and maintains PF >0.95 even at 10% load via accurate current amplifier offset control. |
| Consumer Audio Amplifier | Medical Power Module |
Use Scenario: High-fidelity Class-D amplifier requiring low-noise, low-THD AC input stage. IC Role / Device Role / Timing Role: Boost PFC controller synchronizing leading-edge modulation with downstream PWM to minimize bus ripple. Use Value: Reduces 100/120 Hz ripple on bulk capacitor by 40%, lowering audible noise and improving PSRR. |
Use Scenario: IEC60601-1 compliant 150 W medical AC/DC module with reinforced isolation and low leakage. IC Role / Device Role / Timing Role: Safety-critical PFC controller with OVP/EN pin used for secondary-side fault signaling and shutdown coordination. Use Value: OVP hysteresis (500 mV) prevents nuisance tripping during transient overloads while ensuring fast response to hazardous overvoltage events. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar power factor correction controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC3817AD | 16 V/9.7 V UVLO threshold; integrated shunt regulator for bootstrap supply | Suitable for designs lacking dedicated VCC rail-uses auxiliary winding for self-bias | Select UCC3817AD when VCC must be derived from transformer auxiliary winding |
| UC3854BDW | Higher 15 V UVLO; ACM control but no integrated feed-forward or zero-power detection | Requires external feed-forward circuitry and lacks automatic no-load shutdown | Choose UC3854BDW for legacy designs needing higher UVLO margin and proven field reliability above 300 W |
Compared with UCC3818AD, UCC3817AD supports bootstrap operation but lacks fixed-VCC optimization, while UC3854BDW offers broader power scalability but demands more external components and lacks modern noise immunity features.
Availability
UCC3818AD is available at Aetrix Electronics and suitable for PC power supplies, industrial LED drivers, consumer audio amplifiers, and medical power modules requiring stable component supply across extended production cycles.
Supply support for UCC3818AD 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 company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and communications markets.
The UCC3818AD belongs to TI's UCCx81xA BiCMOS PFC controller family, designed specifically for cost-sensitive, high-efficiency active power factor correction in sub-300 W AC/DC power supplies with fixed-VCC architectures.
FAQ
What is the UVLO behavior of the UCC3818AD?
The UCC3818AD features an undervoltage lockout with 10.2 V turn-on threshold and 9.7 V turn-off threshold, yielding 0.5 V hysteresis. This ensures clean startup once VCC stabilizes above 10.2 V and prevents oscillatory operation near the threshold. Below 9.7 V, the DRVOUT pin is disabled and the internal reference (VREF) shuts down. This behavior is confirmed in the Electrical Characteristics table of the SLUS577D datasheet.
Can the UCC3818AD be used with a bootstrap VCC supply?
No-the UCC3818AD is explicitly designed for fixed-VCC applications and does not integrate a shunt regulator. Unlike the UCC3817A variant, it cannot derive operating power from a transformer auxiliary winding. Attempting bootstrap operation will result in failure to start or unstable regulation. The UCC3817AD is the correct choice for bootstrap topologies.
What is the function of the OVP/EN pin on the UCC3818AD?
The OVP/EN pin serves dual functions: as an overvoltage protection input (triggering shutdown when boost output exceeds a programmed threshold referenced to VREF) and as an enable input (disabling DRVOUT when pulled below 1.9 V). It uses a window comparator architecture with 500 mV hysteresis to prevent chatter during transients. This pin is critical for system safety in medical and industrial applications.
How does the UCC3818AD achieve low THD in PFC operation?
The UCC3818AD achieves low total harmonic distortion through average current mode control, a low-offset (±2 mV) current amplifier, feed-forward line voltage compensation (VFF pin), and leading-edge PWM modulation synchronized to reduce ripple. These features collectively maintain sinusoidal input current even at light loads and across universal AC input ranges, as validated in Figure 2 of the SLUS577D datasheet.
What package options are available for the UCC3818AD?
The UCC3818AD is offered exclusively in the 16-pin SOIC (D) package with body dimensions of 4.90 mm × 3.91 mm. It is not available in PDIP (N) or TSSOP (PW) variants-those are designated for other members of the UCCx81xA family (e.g., UCC3818AN, UCC3818APW). The SOIC package supports surface-mount assembly and meets JEDEC MS-012AC standards.
UCC3818AD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Mode:
- Average Current
- Frequency - Switching:
- 6kHz ~ 220kHz
- Current - Startup:
- 150 µA
- Voltage - Supply:
- 12V ~ 17V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
UCC3818AD FAQ
1.How can I place an order for UCC3818AD through Aetrix?
Please submit a Request for Quotation (RFQ) for UCC3818AD 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 UCC3818AD reliable?
The price and inventory of UCC3818AD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UCC3818AD is usually 5 days.
3.What payment methods are accepted for UCC3818AD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UCC3818AD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UCC3818AD?
UCC3818AD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UCC3818AD 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 UCC3818AD?
For technical support, including UCC3818AD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UCC3818AD requirements.
6.How does Aetrix verify that UCC3818AD is sourced from the original manufacturer or authorized distributors?
All UCC3818AD 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 UCC3818AD meets industry standards.
7.What is the process for return or replacement of UCC3818AD?
All UCC3818AD units undergo pre-shipment inspection (PSI). If there is an issue with UCC3818AD, 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 UCC3818AD part is unused and in its original packaging.
Return procedure for UCC3818AD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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