My Inquiry
My Account
Texas Instruments UCC2804DR81221G4
- Part No.:
- UCC2804DR81221G4
- Manufacturer:
- Texas Instruments
- Category:
- Power Supply Controllers, Monitors
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
UCC2804DR81221G4.pdf
- Description:
- IC OFFLINE SWITCH MULT TOP 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,647
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
UCC2804DR81221G4 from Texas Instruments is a low-power BiCMOS current-mode PWM controller IC designed for off-line fixed-frequency switching power supplies. It features 50% maximum duty cycle, 5V reference voltage with 1.5% tolerance, 12.5V turn-on/8.3V turn-off UVLO thresholds, and 1A totem-pole gate drive output. Used in AC-DC adapters and auxiliary power supplies where high-voltage startup reliability is critical.
For engineers reviewing the UCC2804DR81221G4 datasheet, UCC2804DR81221G4 pinout, UCC2804DR81221G4 application, or UCC2804DR81221G4 equivalent, this page delivers verified electrical parameters, SOIC-8 package mapping, soft-start behavior, leading-edge blanking timing, and real-world alternative selection guidance for current-mode flyback and forward converter designs.
Technical Context
The UCC2804DR81221G4 implements fixed-frequency current-mode control with internal full-cycle soft start and digital leading-edge blanking on the CS pin (50–150 ns). Its oscillator operates up to 1 MHz using external RC timing components, and its error amplifier provides 2 MHz gain-bandwidth product with bidirectional COMP sink/source capability.
This device uses a dedicated 5V bandgap reference (±1.5% over temperature) to set feedback threshold and supports direct interface with optocoupler-based secondary-side regulation. The 70 ns current-sense-to-gate-response time and 1.55 V over-current threshold enable fast fault limiting in high-speed power stages.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Max Duty Cycle | 50% - Enables safe operation in forward converters and limits peak primary current in flyback topologies. |
| Reference Voltage | 5.00 V ±1.5% - Stable precision reference for error amplifier and internal logic; enables accurate FB threshold setting. |
| UVLO Turn-On/Off | 12.5 V / 8.3 V - High hysteresis (4.2 V) ensures robust startup from bulk rectified AC and prevents brownout oscillation. |
| Start-up Current | 100 µA typical - Allows use of high-value, cost-effective VCC startup resistors without excessive power loss. |
| Gate Drive Output | ±1 A totem-pole - Directly drives medium-size MOSFETs (Qg ≤ 20 nC at 100 kHz) without external buffers. |
| CS Leading-Edge Blanking | 50–150 ns - Digitally blanks CS input after OUT rising edge to reject switch-node noise; eliminates need for RC filter. |
| Oscillator Frequency Range | Up to 1 MHz - Supports compact magnetics and high-density layouts in space-constrained AC-DC designs. |
Pinout & Package
UCC2804DR81221G4 is housed in an 8-pin SOIC (D package), RoHS-compliant, with 1.27 mm pitch and 150°C max junction temperature rating. Pin 1 is OUT; pin 4 is GND; pin 5 is FB; pin 6 is COMP; pin 7 is CS; pin 8 is RC; pin 2 is VCC; pin 3 is REF.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OUT (Pin 1) | Power driver output | Drives MOSFET gate directly; actively pulled low during UVLO; capable of ±1 A peak current. |
| VCC (Pin 2) | Supply input | Powered via current-limiting resistor; internal 13.5 V zener clamp protects against transients. |
| REF (Pin 3) | 5 V reference output | Stable 5 V source for external circuitry; requires ≥0.1 µF ceramic bypass to GND for stability. |
| GND (Pin 4) | Signal and power ground | Common return for all analog and power functions; must be low-impedance and star-connected. |
| FB (Pin 5) | Inverting input of error amp | Receives optocoupler or resistor-divider feedback; sensitive to layout-keep trace short and low-capacitance. |
| COMP (Pin 6) | Error amp output / PWM comparator input | Sinks/sources current; clamped during soft start; sets duty cycle via voltage comparison with CS signal. |
| CS (Pin 7) | Current sense input | Accepts shunt or transformer-sensed current; blanked for 50–150 ns after each OUT rise to reject ringing. |
| RC (Pin 8) | Oscillator timing node | Connected to RT (REF→RC) and CT (RC→GND); sets frequency and maximum duty cycle via RC time constant. |
Key Features
| Feature | Design Value |
|---|---|
| Internal full-cycle soft start | COMP voltage ramped over 4–10 ms to prevent inrush current and transformer saturation at power-up. |
| Digital leading-edge blanking | Hardware-based 50–150 ns CS disable window eliminates need for external RC filter and reduces propagation delay vs analog methods. |
| 1.5% reference tolerance | Ensures tight regulation accuracy across –40°C to +85°C ambient, reducing output voltage drift in unregulated auxiliary rails. |
| Same pinout as UC3842/UC3842A | Enables drop-in replacement in legacy UC3842-based designs without PCB modification or schematic change. |
| 70 ns CS-to-OUT response | Supports high-frequency (>500 kHz) operation with fast over-current shutdown, improving safety margin in high-power density SMPS. |
Applications
| AC-DC Adapter Power Supply | Flyback Converter for Industrial Sensors |
|---|---|
|
Use Scenario: 12 V/2 A isolated wall adapter powering IoT gateway devices with variable load profiles. IC Role / Device Role: Primary-side current-mode PWM controller regulating output via optocoupler feedback loop. Use Value: 12.5 V UVLO ensures reliable startup from 90–264 VAC input; 50% duty cycle prevents transformer core saturation under overload. |
Use Scenario: Compact 5 V/0.5 A flyback supply powering analog sensor front-ends in factory automation nodes. IC Role / Device Role: Fixed-frequency current-mode controller with integrated soft start and fault blanking. Use Value: 100 µA start-up current minimizes no-load losses; leading-edge blanking rejects EMI from nearby motor drives. |
| Offline Auxiliary Power for Motor Drives | Forward Converter in Telecom PSU |
|
Use Scenario: 15 V/0.3 A auxiliary rail supplying gate drivers and MCU in 3-phase inverter modules. IC Role / Device Role: Off-line PWM controller operating from rectified DC bus (≈320 V). Use Value: 8.3 V UVLO hysteresis prevents cycling during line dips; 1 A gate drive eliminates need for discrete buffer stage. |
Use Scenario: 24 V/3 A regulated forward converter delivering main bias power in telecom shelf management systems. IC Role / Device Role: Current-mode controller with precise 5 V reference enabling tight cross-regulation across multiple outputs. Use Value: 1.5% reference tolerance maintains <±3% output accuracy across temperature; same pinout allows reuse of UC3842 layout. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar current-mode PWM controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC2804DG4 | Identical electrical specs and SOIC-8 packaging; differs only in tape-and-reel packaging (75 pcs vs 2500 pcs) and part marking. | No functional difference; suitable for prototype or low-volume builds where smaller reels are preferred. | Select UCC2804DG4 for engineering samples or pilot production; UCC2804DR81221G4 is optimized for high-volume manufacturing. |
| UC3842N | Legacy bipolar version; higher start-up current (1 mA), no internal soft start or leading-edge blanking, 2% reference tolerance. | Lacks digital blanking and soft start-requires external RC filter and soft-start circuit; less robust under transient conditions. | Choose UC3842N only for legacy repair or cost-sensitive applications where design margin and EMI immunity are secondary. |
Compared with UCC2804DG4, the UCC2804DR81221G4 offers identical performance in a high-volume tape-and-reel format; versus UC3842N, it delivers superior startup reliability, built-in protection features, and tighter regulation-justifying its use in new industrial and telecom designs.
Availability
UCC2804DR81221G4 is available at Aetrix Electronics and suitable for AC-DC adapters, industrial sensor power supplies, and telecom auxiliary rails requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.
Supply support for UCC2804DR81221G4 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 90 years of innovation history.
The UCC280x family was designed specifically for cost-sensitive, high-reliability off-line current-mode power supplies-emphasizing low start-up current, integrated protection, and pin compatibility with industry-standard UC3842 footprints.
FAQ
What is the operating temperature range for UCC2804DR81221G4?
The UCC2804DR81221G4 is specified for operation from –40°C to +85°C ambient temperature. This industrial-grade range supports deployment in enclosed power supplies, motor drive auxiliary rails, and outdoor-rated industrial equipment without derating. All electrical characteristics-including reference voltage, UVLO thresholds, and oscillator frequency-are guaranteed across this full range.
Does UCC2804DR81221G4 require an external soft-start capacitor?
No, UCC2804DR81221G4 implements internal full-cycle soft start-no external capacitor is needed. The COMP pin voltage ramps from 0 V to REF–1 V over 4–10 ms, controlling duty cycle growth during power-up. This eliminates component count and layout sensitivity associated with external RC soft-start networks used in older controllers like UC3842.
Can UCC2804DR81221G4 replace UC3842 in existing designs?
Yes, UCC2804DR81221G4 has identical pinout and function mapping to UC3842 and UC3842A. It adds internal soft start and leading-edge blanking while maintaining compatible timing, drive strength, and reference levels-enabling drop-in replacement in most UC3842-based flyback and forward converters without PCB or schematic changes.
What is the purpose of the RC pin on UCC2804DR81221G4?
The RC pin on UCC2804DR81221G4 serves as the oscillator timing node. A resistor from REF to RC sets charging current; a capacitor from RC to GND sets frequency. The oscillator generates a sawtooth waveform here, determining switching frequency and influencing maximum duty cycle-key for optimizing transformer size and efficiency in the final power stage.
How does the leading-edge blanking feature work on UCC2804DR81221G4?
UCC2804DR81221G4 digitally disconnects the CS pin from the current-sense comparator for 50–150 ns immediately after each rising edge of the OUT signal. This hardware blanking window rejects high-frequency ringing induced by transformer leakage inductance and MOSFET switching transitions-eliminating the need for external RC filters and reducing total CS-to-OUT propagation delay to 70 ns typical.
UCC2804DR81221G4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- UCC280x
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Programmable:
- -
- Applications:
- PWM Controller
- Voltage - Input:
- -0.3V ~ 6.3V
- Voltage - Supply:
- 6.9V ~ 11V
- Current - Supply:
- 500 µA
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
UCC2804DR81221G4 FAQ
1.How can I place an order for UCC2804DR81221G4 through Aetrix?
Please submit a Request for Quotation (RFQ) for UCC2804DR81221G4 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 UCC2804DR81221G4 reliable?
The price and inventory of UCC2804DR81221G4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UCC2804DR81221G4 is usually 5 days.
3.What payment methods are accepted for UCC2804DR81221G4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UCC2804DR81221G4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UCC2804DR81221G4?
UCC2804DR81221G4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UCC2804DR81221G4 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 UCC2804DR81221G4?
For technical support, including UCC2804DR81221G4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UCC2804DR81221G4 requirements.
6.How does Aetrix verify that UCC2804DR81221G4 is sourced from the original manufacturer or authorized distributors?
All UCC2804DR81221G4 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 UCC2804DR81221G4 meets industry standards.
7.What is the process for return or replacement of UCC2804DR81221G4?
All UCC2804DR81221G4 units undergo pre-shipment inspection (PSI). If there is an issue with UCC2804DR81221G4, 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 UCC2804DR81221G4 part is unused and in its original packaging.
Return procedure for UCC2804DR81221G4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
UCC2804DR81221G4 Tags
-
UC3845AD8TR
Texas Instruments
-
UC2843AD8TR
Texas Instruments
-
LM3880MFX-1AE/NOPB
Texas Instruments
-
LM3880MFX-1AA/NOPB
Texas Instruments
-
INA234AIYBJR
Texas Instruments
-
INA700AYWFR
Texas Instruments
-
LM3880MF-1AE/NOPB
Texas Instruments
-
LM3880MF-1AA/NOPB
Texas Instruments
-
LM3881MM/NOPB
Texas Instruments
-
UCC2802DTR
Texas Instruments
-
NCP4305DMTTWG
onsemi
-
INA237AIDGSR
Texas Instruments
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
