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STMicroelectronics E-UC3844BN
- Part No.:
- E-UC3844BN
- Manufacturer:
- STMicroelectronics
- Category:
- DC DC Switching Controllers
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
E-UC3844BN.pdf
- Description:
- IC REG CTRLR PWM CM 8-MINIDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,322
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Product details
Overview
E-UC3844BN from STMicroelectronics is a high-performance current-mode PWM controller IC designed for fixed-frequency off-line and DC-DC power supplies. It features a trimmed oscillator guaranteed at 250 kHz, internal toggle flip-flop limiting maximum duty cycle to <50%, and UVLO thresholds of 16 V (on) / 10 V (off), optimized for universal-input AC-DC adapters and auxiliary power supplies.
For engineers reviewing the E-UC3844BN datasheet, E-UC3844BN pinout, E-UC3844BN application, or E-UC3844BN equivalent, key selection criteria include its 50% max duty cycle constraint, 1 A peak totem-pole output drive, ±100 µA ISENSE input bias, 5 V ±100 mV reference accuracy, and SO8/Minidip package compatibility with legacy UC384x designs.
Technical Context
The E-UC3844BN implements current-mode control using a comparator that compares sensed inductor current against an error amplifier output, enabling cycle-by-cycle current limiting and inherent feed-forward compensation. Its oscillator uses RT/CT programming with internal discharge current of 7.5–8.8 mA, supporting operation up to 500 kHz.
Unlike UC3842B/3B, it includes an internal toggle flip-flop that blanks the output every other clock cycle-enforcing ≤50% duty cycle for forward converter topologies. The error amplifier has 90 dB open-loop gain, 1 MHz unity-gain bandwidth, and PSRR of 70 dB, ensuring stable regulation under line/load transients.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | Guaranteed 250 kHz at Tj = 25°C (RT = 6.2 kΩ, CT = 1 nF); supports up to 500 kHz with external timing components. |
| Max Duty Cycle | 47–50% due to internal toggle flip-flop-enables safe operation in forward and push-pull converters without external dead-time control. |
| UVLO Thresholds | 16 V turn-on / 10 V turn-off-provides robust start-up and brown-out protection for 85–265 VAC offline inputs after rectification. |
| Reference Voltage | 5.00 V ±100 mV at TJ = 25°C, Io = 1 mA-stable for RT/CT charging and feedback divider biasing with <0.2 mV/°C drift. |
| Output Drive | Totem-pole stage sourcing/sinking ≥1 A peak-directly drives N-channel MOSFET gates without external buffers in ≤30 W designs. |
| ISENSE Input Range | 0–1.1 V full-scale with 3 V/V gain-supports precise current sensing with ≤150 ns delay to output latch activation. |
| Start-up Current | <0.5 mA at Vi = 14 V-minimizes auxiliary winding losses and enables high-impedance VCC startup networks. |
Pinout & Package
E-UC3844BN is available in both SO8 (small-outline) and Minidip (DIP-8) packages. Pin functions are identical across variants and validated per STMicroelectronics D95IN332 diagram.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - COMP | Error amplifier output | Provides access to EA output for Type II/III compensation networks; requires external RC network for loop stability. |
| 2 - VFB | Inverting input of error amplifier | Connected to output voltage divider; sets regulated output via 2.5 V internal reference comparison point. |
| 3 - ISENSE | Current sense comparator input | Accepts voltage from shunt/resistor; terminates switch conduction when signal exceeds EA output level. |
| 4 - RT/CT | Oscillator timing interface | RT connects to VREF (pin 8), CT to GND (pin 5); sets frequency and influences max duty cycle via discharge current. |
| 5 - GROUND | Signal and power return | Single-point ground for control circuitry and power stage return-critical for noise immunity in current-mode operation. |
| 6 - OUTPUT | Gate drive output | Push-pull output capable of ±1 A peak; low-state impedance ensures MOSFET turn-off even under capacitive load conditions. |
| 7 - VCC | Supply input | Operates from 10–30 V; powers internal bias, reference, and logic; UVLO monitoring occurs here. |
| 8 - VREF | 5 V precision reference output | Supplies charging current for CT via RT; used for feedback divider bias and sensor excitation in auxiliary circuits. |
Key Features
| Feature | Design Value |
|---|---|
| Latched PWM with cycle-by-cycle current limit | Prevents transformer saturation and MOSFET overcurrent by forcing single-pulse shutdown until next clock cycle reset. |
| Internally trimmed 5 V reference | ±100 mV tolerance at 25°C eliminates need for external reference ICs in cost-sensitive AC-DC SMPS designs. |
| Automatic feed-forward compensation | Oscillator ramp slope adjusts with input voltage changes-reducing need for complex loop compensation in wide-input applications. |
| Low start-up current (<0.5 mA) | Enables use of high-value startup resistors-reducing standby power loss and thermal stress on auxiliary windings. |
| High-current totem-pole output | Drives 1000 pF gate capacitance with <150 ns rise/fall times-supports fast-switching MOSFETs without external drivers. |
Applications
| AC-DC Adapter | Industrial Auxiliary Supply |
|---|---|
|
Use Scenario: 12 V/2 A isolated flyback converter for laptop adapter with universal AC input (85–265 VAC). IC Role / Device Role / Timing Role: Primary-side PWM controller providing current-mode regulation, cycle-by-cycle current limiting, and 250 kHz switching. Use Value: Internal 50% duty cycle limit prevents core reset issues in discontinuous conduction mode; UVLO ensures reliable start-up across input range. |
Use Scenario: 5 V/1 A auxiliary supply powering microcontrollers and sensors in PLC backplanes. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller regulating output via optocoupler feedback and ISENSE-based primary current sensing. Use Value: Low start-up current (<0.5 mA) minimizes losses during standby; 1 A output drive eliminates need for gate driver ICs. |
| LED Driver (Constant Current) | DC-DC Boost Converter |
|
Use Scenario: Constant-current boost LED driver for streetlight modules (36 V output, 700 mA). IC Role / Device Role / Timing Role: Current-mode PWM controller regulating LED current via ISENSE feedback and fixed 250 kHz switching. Use Value: Precise 3 V/V ISENSE gain enables accurate current sensing with milliohm shunts; 5 V reference stabilizes feedback divider. |
Use Scenario: 12 V to 24 V boost converter for battery-powered industrial telemetry units. IC Role / Device Role / Timing Role: High-efficiency current-mode controller implementing voltage-mode-like stability via feed-forward compensation. Use Value: Automatic feed-forward reduces output ripple under line transients; 500 kHz capability allows compact magnetics and low-profile design. |
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 |
|---|---|---|---|
| UC3844BD1 (SO8) | Same electrical specs and pinout; differs only in packaging (SO8 vs. Minidip) and tape-and-reel vs. tube packaging. | Identical functional use; preferred for automated SMT assembly due to SO8 footprint. | Select when surface-mount manufacturing is required and board layout accommodates SO8 pitch. |
| NCP1200DR2G | Fixed-frequency current-mode controller with 700 kHz max, integrated soft-start, and lower start-up current (80 µA), but no internal 5 V reference. | Suited for higher-frequency, lower-power (<15 W) applications where soft-start and ultra-low standby matter more than reference availability. | Choose for new designs prioritizing efficiency and integration; avoid if existing feedback network relies on 5 V VREF. |
Compared with UC3844BD1, E-UC3844BN offers identical performance in Minidip form for through-hole prototyping or legacy repair. Against NCP1200DR2G, it trades higher start-up current and no soft-start for built-in 5 V reference and proven 250 kHz stability in mid-power flyback designs.
Availability
E-UC3844BN is available at Aetrix Electronics and suitable for AC-DC adapters, industrial auxiliary supplies, LED drivers, and DC-DC boost converters requiring stable component supply, long-term lifecycle support, and drop-in compatibility with legacy UC384x designs.
Supply support for E-UC3844BN 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, specializing in power management, analog, MCU, and automotive ICs with vertical manufacturing and broad industrial qualification.
The UC384xB family was engineered for cost-effective, high-reliability current-mode switching power supplies-targeting off-line AC-DC conversion, telecom brick supplies, and industrial auxiliary rails where simplicity, stability, and ruggedness are critical.
FAQ
What is the maximum operating frequency of E-UC3844BN?
E-UC3844BN guarantees 250 kHz oscillator frequency at 25°C with RT = 6.2 kΩ and CT = 1 nF, and supports operation up to 500 kHz with appropriate RT/CT values and layout optimization. Frequency stability degrades above 500 kHz due to propagation delays and oscillator discharge current limits.
Why does E-UC3844BN have a 50% maximum duty cycle?
The 50% limit results from an internal toggle flip-flop that disables the output every other clock cycle-a deliberate design for forward and push-pull converters to prevent transformer core saturation. This distinguishes it from UC3842B/3B, which support up to 100% duty cycle.
Can E-UC3844BN drive a P-channel MOSFET directly?
No-it features a totem-pole output optimized for sinking current into N-channel MOSFET gates. Driving a P-channel device would require level-shifting circuitry or an external inverter, as the output cannot actively pull high above VCC and lacks high-side drive capability.
Is the 5 V reference output (pin 8) buffered?
Yes-the VREF pin provides a buffered 5 V output capable of sourcing up to 50 mA (per absolute maximum ratings), though typical applications draw <1 mA for RT biasing. Load regulation is ±25 mV from 1–20 mA, confirming internal buffering for stable timing and feedback biasing.
E-UC3844BN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- 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:
- Through Hole
- Supplier Device Package:
- 8-Mini DIP
E-UC3844BN FAQ
1.How can I place an order for E-UC3844BN through Aetrix?
Please submit a Request for Quotation (RFQ) for E-UC3844BN 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-UC3844BN reliable?
The price and inventory of E-UC3844BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for E-UC3844BN is usually 5 days.
3.What payment methods are accepted for E-UC3844BN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for E-UC3844BN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for E-UC3844BN?
E-UC3844BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your E-UC3844BN 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-UC3844BN?
For technical support, including E-UC3844BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your E-UC3844BN requirements.
6.How does Aetrix verify that E-UC3844BN is sourced from the original manufacturer or authorized distributors?
All E-UC3844BN 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-UC3844BN meets industry standards.
7.What is the process for return or replacement of E-UC3844BN?
All E-UC3844BN units undergo pre-shipment inspection (PSI). If there is an issue with E-UC3844BN, 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-UC3844BN part is unused and in its original packaging.
Return procedure for E-UC3844BN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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