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STMicroelectronics E-UC3844BD1
- Part No.:
- E-UC3844BD1
- Manufacturer:
- STMicroelectronics
- Category:
- DC DC Switching Controllers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
E-UC3844BD1.pdf
- Description:
- IC REG CTRLR BST FLYBK ISO 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,740
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Product details
Overview
E-UC3844BD1 from STMicroelectronics is a high-performance current-mode PWM controller IC designed for off-line and DC-DC fixed-frequency power supplies. It features a trimmed oscillator guaranteed at 250 kHz, 47–50% maximum duty cycle (due to internal toggle flip-flop), UVLO thresholds of 16 V (on) / 10 V (off), and a totem-pole output capable of ±1 A peak drive - enabling direct N-channel MOSFET gate control in flyback and forward converters.
For engineers reviewing the E-UC3844BD1 datasheet, E-UC3844BD1 pinout, E-UC3844BD1 application, or E-UC3844BD1 equivalent, key selection criteria include its 50% duty-cycle limit, 250 kHz oscillator accuracy, 5 V ±1% reference, latch-type PWM for cycle-by-cycle current limiting, and SO8 package compatibility with legacy UC384xB designs.
Technical Context
The E-UC3844BD1 implements current-mode control with automatic feed-forward compensation and a latched PWM comparator that terminates switch conduction based on sensed inductor current. Its internal toggle flip-flop blanks the output every other clock cycle - enforcing ≤50% duty cycle for stability in isolated topologies requiring voltage-mode-like behavior.
Oscillator frequency is set via external RT/CT network (250 kHz typical with RT = 6.2 kΩ, CT = 1 nF); the 5 V reference provides precise biasing for error amplifier and timing components. Under-voltage lockout includes hysteresis (6 V window), and start-up current is <0.5 mA - critical for low-power auxiliary supply design.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 250 kHz (guaranteed at Tj = 25°C; supports up to 500 kHz with external tuning) |
| Max Duty Cycle | 47–50% (enforced by internal toggle flip-flop - prevents subharmonic oscillation in flyback) |
| VREF Output | 5.00 V ±1% (trimmed, 1 mA load; powers RT/CT network and error amp bias) |
| UVLO Thresholds | 16 V (turn-on), 10 V (turn-off) - ensures reliable startup and brownout protection in AC/DC adapters |
| Output Drive | ±1 A peak (totem-pole stage; directly drives MOSFET gates without external buffer) |
| Current Sense Gain | 3.0 V/V ±5% (converts sense resistor voltage to PWM trip point; enables accurate peak-current limiting) |
| Error Amp GBW | 0.7–1 MHz (supports stable loop compensation for 20–100 kHz switching frequencies) |
Pinout & Package
Package: SO8 (Small Outline Integrated Circuit, 150 °C/W thermal resistance, JEDEC MS-012AC compliant).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - COMP | Error amplifier output | Provides access to EA output for Type II/III loop compensation networks |
| 2 - VFB | Inverting input of error amplifier | Connected to output voltage divider; sets regulation point via 2.5 V internal reference |
| 3 - ISENSE | Current sense input | Receives voltage from primary-side sense resistor; triggers PWM latch at 1 V threshold |
| 4 - RT/CT | Oscillator timing node | RT to VREF + CT to GND sets fOSC and max duty cycle; CT discharge current = 7.5–8.8 mA |
| 5 - GROUND | Power and signal common | Single-point ground reference for control circuitry and current sense return path |
| 6 - OUTPUT | PWM output driver | Drives MOSFET gate low during off-time; sinks/source up to 1 A peak |
| 7 - VCC | Supply input | Accepts 10–30 V; powers internal bias, reference, and logic; UVLO active below 10 V |
| 8 - VREF | 5 V reference output | Stable 5 V source for RT bias and external circuitry; short-circuit protected (−180 mA min) |
Key Features
| Feature | Design Value |
|---|---|
| Latched PWM with cycle-by-cycle current limiting | Prevents transformer saturation and MOSFET overcurrent by forcing one-shot shutdown per fault event |
| Internally trimmed 5 V reference (±1%) | Eliminates need for external reference IC; improves regulation accuracy and reduces BOM count |
| Low start-up current (<0.5 mA) | Enables use of high-value startup resistors - reduces standby power loss in offline SMPS |
| Automatic feed-forward compensation | Rejects line voltage variations in real time - improves transient response without additional feedback paths |
| High-current totem-pole output (±1 A) | Directly drives 10 nC gate charge MOSFETs at 250 kHz without external driver stage |
Applications
| AC/DC Adapter | Flyback Power Supply |
|---|---|
|
Use Scenario: 12 V/2 A universal-input offline adapter for consumer electronics. IC Role / Device Role / Timing Role: Primary-side PWM controller regulating output via optocoupler feedback; generates 250 kHz gate drive with 48% duty cycle. Use Value: 50% duty-cycle limit prevents subharmonic instability under heavy load and wide input range (90–264 VAC). |
Use Scenario: Isolated 5 V/3 A medical-grade flyback converter meeting IEC 60601 creepage requirements. IC Role / Device Role / Timing Role: Current-mode controller implementing primary-side sensing and latch protection against overload. Use Value: Latched shutdown and <0.5 mA start-up current ensure safe, low-power operation during fault conditions and standby. |
| Industrial DC/DC Converter | LED Driver (Constant Voltage) |
|
Use Scenario: 24 V input to ±15 V dual-output DC/DC module for PLC I/O modules. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller driving forward topology with synchronous rectification. Use Value: 250 kHz oscillator accuracy and 3 V/V current sense gain enable precise peak-current control across temperature (−40 to +105°C). |
Use Scenario: Constant-voltage LED driver powering 12 V string in architectural lighting. IC Role / Device Role / Timing Role: PWM controller regulating bulk capacitor voltage via secondary-side feedback; operates in discontinuous conduction mode. Use Value: 5 V reference and 100% input voltage feed-forward allow stable dimming performance across 10–30 V input range. |
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 |
|---|---|---|---|
| UCC3803D | Higher UVLO (16.5 V on / 10.5 V off), same 50% duty cycle, but lower operating current (12 mA vs 17 mA) | Optimized for ultra-low standby power; lacks internal trim for VREF (requires external 2.5 V reference) | Select when minimizing no-load consumption is critical and external reference is acceptable |
| NCP1207AD | Includes soft-start, frequency foldback, and built-in slope compensation; 65 kHz fixed frequency (not adjustable) | Targeted at cost-sensitive consumer adapters; no RT/CT programming - less flexible for custom designs | Select for plug-and-play implementation where 65 kHz operation and integrated protections suffice |
Compared with UCC3803D and NCP1207AD, E-UC3844BD1 offers field-programmable oscillator frequency, precise internal 5 V reference, and proven robustness in industrial flyback designs - making it preferred where design flexibility, regulation accuracy, and long-term supply continuity matter.
Availability
E-UC3844BD1 is available at Aetrix Electronics and suitable for AC/DC adapters, flyback power supplies, and industrial DC/DC converters requiring stable component supply, long-lifecycle support, and SO8 footprint compatibility with legacy UC384xB designs.
Supply support for E-UC3844BD1 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, delivering silicon solutions for automotive, industrial, and power management applications.
E-UC3844BD1 belongs to the UC384xB family of current-mode PWM controllers - engineered specifically for cost-effective, high-reliability off-line and isolated DC/DC power conversion with minimal external components.
FAQ
What is the maximum recommended switching frequency for E-UC3844BD1?
The E-UC3844BD1 supports up to 500 kHz operation with appropriate RT/CT values and layout optimization. However, its guaranteed oscillator frequency is 250 kHz at 25°C. At higher frequencies, propagation delays and output rise/fall times (50–150 ns) become limiting factors - especially with capacitive gate loads exceeding 1 nF. For reliable 500 kHz operation, minimize PCB trace inductance and use low-ESR timing capacitors.
Does E-UC3844BD1 require external slope compensation?
No - slope compensation is not required for E-UC3844BD1 in most flyback applications due to its inherent 50% maximum duty cycle limitation. The internal toggle flip-flop prevents subharmonic oscillation that would otherwise necessitate external ramp injection. However, if operating near the 50% boundary with variable input voltage or high transformer turns ratio, a small RC filter on the ISENSE pin may improve noise immunity without full slope compensation.
How does the UVLO hysteresis affect system startup behavior?
E-UC3844BD1 has a 6 V UVLO hysteresis (16 V turn-on, 10 V turn-off). During startup, the IC remains disabled until VCC rises above 16 V - typically achieved via high-value resistor from rectified AC. Once enabled, it continues operating down to 10 V, preventing nuisance shutdown during brief line sags. This hysteresis ensures clean, bounce-free activation and avoids oscillatory behavior during marginal input conditions.
Can E-UC3844BD1 drive a P-channel MOSFET directly?
No - E-UC3844BD1's OUTPUT pin is a totem-pole stage referenced to GROUND and designed to sink/source current into an N-channel MOSFET gate. Driving a P-channel device requires level-shifting circuitry or an external driver, because the IC cannot pull its output above VCC. Its architecture assumes low-side gate drive configuration; using it for high-side P-MOSFET control introduces timing mismatches and shoot-through risk without additional logic.
E-UC3844BD1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Output Type:
- Transistor Driver
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Boost, Flyback
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 10V ~ 30V
- Frequency - Switching:
- Up to 500kHz
- Duty Cycle (Max):
- 48%
- Synchronous Rectifier:
- No
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Frequency Control
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
E-UC3844BD1 FAQ
1.How can I place an order for E-UC3844BD1 through Aetrix?
Please submit a Request for Quotation (RFQ) for E-UC3844BD1 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 E-UC3844BD1 reliable?
The price and inventory of E-UC3844BD1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for E-UC3844BD1 is usually 5 days.
3.What payment methods are accepted for E-UC3844BD1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for E-UC3844BD1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for E-UC3844BD1?
E-UC3844BD1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your E-UC3844BD1 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 E-UC3844BD1?
For technical support, including E-UC3844BD1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your E-UC3844BD1 requirements.
6.How does Aetrix verify that E-UC3844BD1 is sourced from the original manufacturer or authorized distributors?
All E-UC3844BD1 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 E-UC3844BD1 meets industry standards.
7.What is the process for return or replacement of E-UC3844BD1?
All E-UC3844BD1 units undergo pre-shipment inspection (PSI). If there is an issue with E-UC3844BD1, 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 E-UC3844BD1 part is unused and in its original packaging.
Return procedure for E-UC3844BD1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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