My Inquiry
My Account
STMicroelectronics UC3844BN
- Part No.:
- UC3844BN
- Manufacturer:
- STMicroelectronics
- Category:
- DC DC Switching Controllers
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
UC3844BN.pdf
- Description:
- IC REG CTRLR PWM CM 8-MINIDIP
- Quantity:
- Payment:
- Shipping:
Inventory:274
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
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, <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 for N-channel MOSFETs - commonly used in 24–48 V input AC/DC adapters and isolated flyback converters.
For engineers reviewing the UC3844BN datasheet, UC3844BN pinout, UC3844BN application, or UC3844BN equivalent, key selection criteria include its 250 kHz oscillator frequency guarantee, 16 V/10 V UVLO hysteresis, <50% duty cycle limitation, 5 V ±1% reference accuracy, and compatibility with standard current-sense resistor-based overcurrent protection in single-ended forward/flyback topologies.
Technical Context
The UC3844BN implements current-mode control via a high-speed current-sense comparator that terminates each switching cycle when sensed inductor current reaches the error amplifier's output voltage level. Its oscillator uses an external RT/CT network with internal discharge current trimming (7.8–8.8 mA), enabling stable operation up to 500 kHz despite supply voltage or temperature variation.
Unlike UC3842BN/3BN, the UC3844BN includes an internal toggle flip-flop that blanks the output every other clock cycle - enforcing a hard-limited maximum duty cycle of ≤50%. This architecture eliminates need for external dead-time control in push-pull or half-bridge configurations while maintaining cycle-by-cycle current limiting and automatic feed-forward compensation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | Guaranteed 250 kHz at 25°C; programmable up to 500 kHz via RT/CT - enables compact magnetics and EMI spread. |
| Max Duty Cycle | ≤48% typical (47–50% range); enforced by internal toggle flip-flop - prevents transformer saturation in push-pull designs. |
| UVLO Thresholds | 16 V turn-on / 10 V turn-off with hysteresis - ensures reliable start-up from bulk rectified AC and brown-out immunity. |
| Reference Voltage | 5.00 V ±1% at 1 mA load; 0.2 mV/°C tempco - provides stable feedback reference for precision output regulation. |
| Output Drive | ±1 A peak sink/source capability; 0.4 V low-level saturation at 20 mA - directly drives gate of medium-power MOSFETs without buffer. |
| Current Sense Gain | 3.0 V/V ±5%; 1.0 V max input threshold - sets accurate current limit point with minimal external sensing resistor drift. |
| Start-up Current | <0.5 mA at 6.5 V - reduces auxiliary winding losses and enables high-impedance bias networks. |
Pinout & Package
UC3844BN is housed in an 8-pin MiniDIP package (body width 7.95–9.75 mm, lead pitch 2.54 mm), suitable for through-hole prototyping and industrial PCB assembly with standard wave soldering profiles.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - COMP | Error amplifier output | Provides access to EA output for loop compensation (e.g., Type II/III networks); high-impedance node requiring low-leakage capacitor. |
| 2 - VFB | Inverting input of error amplifier | Connects to output voltage divider; sets regulated output voltage via 2.5 V internal reference comparison point. |
| 3 - ISENSE | Current sense input | Receives voltage from sense resistor; comparator trips at ~1.0 V to terminate switch conduction - enables cycle-by-cycle current limiting. |
| 4 - RT/CT | Oscillator timing interface | RT connects to VREF (pin 8), CT to ground; sets fOSC and influences max duty cycle via discharge current (7.8–8.8 mA). |
| 5 - GROUND | Signal and power return | Single-point ground for control logic, reference, and oscillator - must be routed separately from power ground to avoid noise coupling. |
| 6 - OUTPUT | Gate driver output | Totem-pole stage sourcing/sinking ±1 A; low-state voltage ≤0.4 V at 20 mA - directly interfaces with MOSFET gate without level-shifting. |
| 7 - VCC | Supply input | Operates from 10–30 V; under-voltage lockout disables output below 10 V - protects against unstable regulation during brown-out. |
| 8 - VREF | 5 V reference output | Supplies charging current for CT via RT; ±1% accuracy and 25 mA short-circuit rating - powers external circuitry or bias networks. |
Key Features
| Feature | Design Value |
|---|---|
| Latched PWM with cycle-by-cycle current limiting | Ensures immediate shutdown on overcurrent event; prevents MOSFET failure during short-circuit or overload conditions. |
| Internally trimmed 5 V reference with <1% tolerance | Eliminates need for external reference IC; maintains output regulation accuracy across line/load/temperature without calibration. |
| Toggle flip-flop–limited 50% max duty cycle | Removes risk of transformer core saturation in push-pull or half-bridge topologies - no external duty clamp required. |
| Low-startup current (<0.5 mA) | Enables use of high-value startup resistors; reduces standby power loss and thermal stress on auxiliary winding components. |
| High-current totem-pole output (±1 A) | Drives MOSFET gates with fast rise/fall times (50–150 ns); supports >100 kHz switching without external driver stage. |
Applications
| AC/DC Adapter | Flyback SMPS |
|---|---|
Use Scenario: 24 V input, 5 V/3 A isolated output for industrial IoT gateway power supply. IC Role / Device Role / Timing Role: Primary-side PWM controller generating gate drive for power MOSFET; regulates output via optocoupler feedback to VFB pin. Use Value: 250 kHz fixed frequency enables small transformer and EMI filter; 16 V/10 V UVLO ensures robust start-up after AC line interruption. |
Use Scenario: 36–75 V DC input telecom power module delivering 12 V/5 A with tight cross-regulation. IC Role / Device Role / Timing Role: Current-mode controller implementing primary-side sensing with slope compensation; manages duty cycle per cycle using ISENSE input. Use Value: ≤50% max duty cycle prevents transformer reset issues in discontinuous conduction mode; 5 V reference stabilizes feedback path accuracy. |
| Push-Pull Converter | Isolated DC-DC Module |
Use Scenario: 48 V bus-powered push-pull converter for railway signaling equipment requiring dual ±15 V outputs. IC Role / Device Role / Timing Role: Master oscillator and gate driver for complementary MOSFET pair; toggle flip-flop enforces alternating phase operation. Use Value: Built-in 50% duty cycle cap eliminates external dead-time generator; UVLO hysteresis prevents chattering during low-line dips. |
Use Scenario: Compact 12 V input, 3.3 V/2 A isolated module for medical sensor interface with reinforced creepage/clearance. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller with opto-isolated feedback; COMP pin used for Type II compensation network. Use Value: Low operating current (12–17 mA) minimizes self-heating in sealed enclosures; SO8-compatible MiniDIP allows conformal coating. |
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 |
|---|---|---|---|
| UC3844D8TR | SO8 surface-mount package; identical electrical specs and pinout; 800 mW power dissipation rating vs. 1.25 W for MiniDIP. | Suitable for automated SMT production; requires reflow profile compatible with plastic body; less suited for high-vibration environments. | Select for volume PCB assembly where board space and pick-and-place efficiency outweigh manual repairability. |
| TL494CN | Fixed-frequency voltage-mode controller; dual-output with adjustable dead time; no built-in current sense comparator or 5 V reference. | Requires external current sensing and reference; supports 0–100% duty cycle but lacks cycle-by-cycle limiting - higher design complexity for overcurrent protection. | Choose only when dual-output push-pull or full-bridge topology is needed and current-mode control is not mandatory. |
Compared with UC3844BN, UC3844D8TR offers identical functionality in a smaller footprint but lower thermal margin, while TL494CN demands additional external components to achieve comparable protection and regulation - making UC3844BN optimal for cost-sensitive, single-MOSFET, current-mode flyback or push-pull designs.
Availability
UC3844BN is available at Aetrix Electronics and suitable for AC/DC adapters, isolated flyback SMPS, push-pull converters, and industrial DC-DC modules requiring stable component supply with long-term manufacturability and consistent parametric performance.
Supply support for 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, microcontrollers, and automotive-grade ICs.
The UC384xB series was developed specifically for cost-effective, high-reliability current-mode switching power supplies - targeting off-line AC/DC conversion, telecom DC-DC, and industrial power applications where cycle-by-cycle current limiting and precise frequency control are critical.
FAQ
What is the maximum recommended oscillator frequency for UC3844BN?
The UC3844BN supports oscillator frequencies up to 500 kHz, verified by electrical characterization with RT = 6.2 kΩ and CT = 1 nF at 25°C. Operation above 250 kHz requires careful layout to minimize noise coupling into ISENSE and COMP pins, and may reduce achievable duty cycle due to propagation delays in the internal latch and comparator.
Can UC3844BN replace UC3842BN in an existing design?
No - UC3844BN cannot directly replace UC3842BN without circuit modification. The UC3844BN enforces ≤50% maximum duty cycle via internal toggle flip-flop, whereas UC3842BN supports up to 100%. Using UC3844BN in a UC3842BN design will halve effective duty cycle, causing output voltage drop or regulation failure unless transformer turns ratio and feedback gain are recalculated.
Does UC3844BN require external slope compensation?
External slope compensation is recommended for UC3844BN when operating in continuous conduction mode (CCM) with duty cycles >25%, especially in boost or flyback topologies. While the device includes automatic feed-forward compensation, CCM stability requires adding a ramp signal to the ISENSE pin to prevent subharmonic oscillation - typically implemented with a resistor from VREF to ISENSE and small capacitor to ground.
What is the purpose of the COMP pin, and how should it be configured?
The COMP pin is the error amplifier output, used to connect a Type II or Type III compensation network between COMP and VFB. It sets loop bandwidth and phase margin for stable regulation. A typical configuration uses a series RC from COMP to VFB plus parallel capacitor from VFB to ground - values selected based on power stage poles/zeros and desired crossover frequency (typically 5–10 kHz for 250 kHz switching).
UC3844BN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Up, 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 (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-Mini DIP
UC3844BN FAQ
1.How can I place an order for UC3844BN through Aetrix?
Please submit a Request for Quotation (RFQ) for 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 UC3844BN reliable?
The price and inventory of UC3844BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3844BN is usually 5 days.
3.What payment methods are accepted for UC3844BN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3844BN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC3844BN?
UC3844BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 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 UC3844BN?
For technical support, including UC3844BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3844BN requirements.
6.How does Aetrix verify that UC3844BN is sourced from the original manufacturer or authorized distributors?
All 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 UC3844BN meets industry standards.
7.What is the process for return or replacement of UC3844BN?
All UC3844BN units undergo pre-shipment inspection (PSI). If there is an issue with 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 UC3844BN part is unused and in its original packaging.
Return procedure for UC3844BN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
UC3844BN Tags
-
UCC28C45DR
Texas Instruments
-
UCC28C40DR
Texas Instruments
-
UCC28C43DR
Texas Instruments
-
ZXSC410E6TA
Diodes Incorporated
-
LM3524DMX/NOPB
Texas Instruments
-
LM3489MMX/NOPB
Texas Instruments
-
MIC2102YML-TR
Microchip Technology
-
LM5148RGYR
Texas Instruments
-
TL598CDR
Texas Instruments
-
LM5155DSSR
Texas Instruments
-
LM25085MYX/NOPB
Texas Instruments
-
UCC2813DTR-0
Texas Instruments
Tech Hub
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…
LDO regulator guide covering low dropout voltage, power dissipation, thermal design, PSRR, output noise, capacitor stability, adjustable LDO circuits, LDO vs buck converter and datasheet selection chec…
Conditional Access Module guide covering CAM meaning, CI/CI+ interface, smart card authorization, DVB security workflow, TV and set-top box compatibility, internal electronics, ESD protection, connecto…
Guide to electronic component obsolescence covering EOL risk, PCN/PDN notices, last-time buy planning, replacement options, form-fit-function validation, counterfeit risk and BOM lifecycle management.
18650 battery guide covering lithium-ion cell basics, 3.6V/3.7V voltage, 4.2V charging, mAh and Wh capacity, protected cells, chargers, BMS, series-parallel packs, holders, welding and sourcing checks.…
Hall effect sensor guide covering working principle, linear and digital sensors, Arduino circuits, current sensing, speed detection, automotive applications, A3144 examples, signal filtering and datash…
Product Change Notification guide for electronic components, covering PCN meaning, PCN vs PDN/EOL, common change types, risk levels, form-fit-function review, engineering validation, BOM control, LTB/L…
A practical guide to blend door actuators, covering HVAC function, symptoms, location, AC and heater issues, reset and calibration, replacement cost, electrical diagnosis, compatibility checks, and rep…
