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STMicroelectronics UC2844BN
- Part No.:
- UC2844BN
- Manufacturer:
- STMicroelectronics
- Category:
- DC DC Switching Controllers
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
UC2844BN.pdf
- Description:
- IC REG CTRLR PWM CM 8-MINIDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,512
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Product details
Overview
UC2844BN from STMicroelectronics is a high-performance current-mode PWM controller IC designed for fixed-frequency DC-DC and off-line power supplies. It features a trimmed oscillator (guaranteed 250 kHz), latching PWM for cycle-by-cycle current limiting, internal toggle flip-flop limiting max duty cycle to <50%, under-voltage lockout (16 V on / 10 V off), and a 5 V ±1% reference with <0.2 mV/°C drift - used in AC-DC adapters and industrial SMPS.
For engineers reviewing the UC2844BN datasheet, UC2844BN pinout, UC2844BN application, or UC2844BN equivalent, key selection criteria include UVLO threshold compatibility, 50% duty-cycle constraint, peak output drive capability (±1 A), and SO8/Minidip package thermal limits (1.25 W at 25°C ambient).
Technical Context
The UC2844BN implements current-mode control using an internal error amplifier, PWM comparator with current-sense input (trip threshold = 1 V), and oscillator programmed via RT/CT network. Its internal toggle flip-flop blanks the output every other clock cycle, enforcing ≤50% maximum duty cycle - distinguishing it from UC2842BN/3BN.
It integrates a 5 V reference with ±10 mV initial accuracy and <25 mV total variation across line/load/temperature, low-startup current (<0.5 mA), and a totem-pole output stage capable of sourcing/sinking up to 1 A peak into N-channel MOSFET gates - all operating over –40°C to +150°C junction temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | Guaranteed 250 kHz at 25°C; supports up to 500 kHz with external RT/CT tuning. |
| Max Duty Cycle | 47–50% - enforced by internal toggle flip-flop; prevents transformer saturation in forward converters. |
| UVLO Threshold | 16 V (turn-on), 10 V (turn-off) - enables reliable start-up in offline 115/230 VAC applications. |
| Reference Voltage | 5.00 V ±10 mV at 25°C; <25 mV total variation across line/load/temp - ensures stable feedback loop reference. |
| Output Drive | ±1 A peak sink/source - directly drives gate capacitance of medium-power MOSFETs without buffer. |
| Current Sense Gain | 3.0 V/V ±5% - converts sensed resistor voltage to precise 1 V trip point for accurate peak-current limiting. |
| Startup Current | <0.5 mA at Vi = 6.5 V - minimizes auxiliary supply burden during initial power-up. |
Pinout & Package
UC2844BN is available in 8-pin Minidip (PDIP-8) and SO8 packages. The Minidip variant has thermal resistance Rth j-amb = 100°C/W and max power dissipation of 1.25 W at Tamb ≤ 25°C.
| 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 external RC network. |
| 2 - VFB | Inverting input of error amplifier | Connected to output voltage divider; sets regulation point when COMP voltage equals internal 2.5 V reference. |
| 3 - ISENSE | Current sense input | Accepts voltage proportional to primary-side current; triggers PWM latch at 1 V threshold for cycle-by-cycle limiting. |
| 4 - RT/CT | Oscillator timing interface | RT to VREF and CT to GND set frequency and dead time; supports 100 kHz–500 kHz range with stable jitter performance. |
| 5 - GROUND | Signal and power return | Single-point ground for control circuitry and power stage; critical for noise immunity in current-mode operation. |
| 6 - OUTPUT | Gate drive output | Totem-pole stage sinks or sources up to 1 A; low-state voltage ≤0.4 V at 20 mA - ensures MOSFET turn-off robustness. |
| 7 - VCC | Supply input | Operates from 10–30 V; internal zener clamps at 30–36 V - allows direct rectified AC or bulk DC input connection. |
| 8 - VREF | 5 V reference output | Supplies charging current to CT via RT; load-regulated to ±25 mV over 1–20 mA - powers external timing and sensing circuits. |
Key Features
| Feature | Design Value |
|---|---|
| Latched PWM with cycle-by-cycle current limit | Prevents runaway during overload or short-circuit by forcing single-cycle shutdown until next clock edge. |
| Internally trimmed 5 V reference | ±10 mV initial accuracy and <0.2 mV/°C drift - eliminates need for external reference in cost-sensitive designs. |
| Toggle flip-flop duty-cycle limiter | Hard-clamps max duty to ≤50% - enables safe operation in forward, push-pull, and half-bridge topologies. |
| Low-startup current (<0.5 mA) | Reduces auxiliary winding size and losses in flyback adapters; supports high-impedance startup networks. |
| High-current totem-pole output | ±1 A peak drive capability - eliminates gate driver IC in sub-100 W applications, reducing BOM count and layout area. |
Applications
| AC-DC Adapter | Industrial SMPS |
|---|---|
|
Use Scenario: 12 V/3 A isolated flyback converter for laptop adapter. IC Role / Device Role / Timing Role: Primary-side PWM controller implementing current-mode regulation and UVLO-based brownout protection. Use Value: 50% duty-cycle limit prevents transformer core saturation during line transients; 16 V/10 V UVLO ensures clean start-up after AC dropout. |
Use Scenario: 24 V/10 A forward converter powering PLC I/O modules. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller with external slope compensation and synchronous rectification timing. Use Value: ±1 A output drive directly switches 50 mΩ MOSFETs; 250 kHz operation enables compact magnetics and EMI filtering. |
| LED Driver | Telecom Power Supply |
|
Use Scenario: Constant-current 48 V/1.5 A LED string driver with analog dimming. IC Role / Device Role / Timing Role: Current-mode controller regulating LED current via secondary-side sense feedback and optocoupler isolation. Use Value: Trimmed 5 V reference stabilizes optocoupler biasing; low-tempco reference ensures dimming linearity over –20°C to +70°C. |
Use Scenario: –48 V input, 3.3 V/20 A telecom DC-DC brick using active clamp forward topology. IC Role / Device Role / Timing Role: Primary-side PWM generator with synchronized multi-phase capability via external clock input. Use Value: RT/CT programmability enables precise 250 kHz switching to meet EN55022 Class B conducted EMI limits; latch protection avoids fault propagation. |
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 |
|---|---|---|---|
| UC3844BN | Same pinout and function but rated for 0°C to +70°C ambient (vs. UC2844BN's –40°C to +150°C junction range). | Not qualified for extended industrial or automotive environments requiring full –40°C cold-start capability. | Select UC2844BN for wide-temperature deployments; UC3844BN only where commercial temp grade suffices. |
| TL494CN | Fixed-frequency voltage-mode controller with dual outputs, adjustable dead time, and built-in error amps - no integrated current sense comparator or UVLO. | Requires external current sensing and protection logic; lacks cycle-by-cycle limiting and auto-restart latch behavior. | Choose TL494CN only when dual-output push-pull or full-bridge topologies are needed; not drop-in for UC2844BN current-mode designs. |
Compared with UC3844BN, the UC2844BN offers extended temperature qualification and higher reliability margin; versus TL494CN, it delivers integrated current-mode control with simpler BOM and faster transient response - critical for flyback and forward converters.
Availability
UC2844BN is available at Aetrix Electronics and suitable for AC-DC adapters, industrial SMPS, LED drivers, and telecom power supplies requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.
Supply support for UC2844BN 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 ICs - with over 40 years of analog control IC heritage.
The UCx84xB family was developed specifically for cost-effective, high-reliability current-mode switch-mode power supplies - targeting offline and DC-DC applications where precision timing, robust fault handling, and minimal external components are essential.
FAQ
What is the maximum recommended oscillator frequency for stable operation of UC2844BN?
The UC2844BN supports oscillator frequencies up to 500 kHz with appropriate RT/CT selection and PCB layout care. However, guaranteed 250 kHz operation is specified at 25°C; above 350 kHz, propagation delays and gate drive slew rate become limiting factors - especially with capacitive loads >1 nF. For production designs, 250–300 kHz is preferred to maintain timing margin and EMI control.
Can UC2844BN be used in continuous conduction mode (CCM) flyback converters?
Yes, UC2844BN is commonly used in CCM flyback designs. Its current-mode architecture provides inherent slope compensation via the internal oscillator ramp, and the 50% duty-cycle limit prevents subharmonic oscillation - eliminating need for external ramp injection in most cases. Designers must ensure the current-sense resistor value yields ≤1 V at peak primary current to avoid premature PWM termination.
How does the UC2844BN's UVLO behavior differ from UC2842BN?
Both UC2842BN and UC2844BN share identical UVLO thresholds: 16 V turn-on and 10 V turn-off. The functional difference lies solely in maximum duty cycle - UC2842BN supports up to 100%, while UC2844BN caps at 50% due to its internal toggle flip-flop. This makes UC2844BN unsuitable for boost or buck topologies requiring >50% duty, but ideal for forward and push-pull where duty symmetry matters.
Is the VREF pin (Pin 8) capable of sourcing current to external circuitry?
Yes, Pin 8 (VREF) is specified to source up to 20 mA while maintaining regulation within ±25 mV. It supplies charging current to the CT capacitor through RT and can power small-signal bias networks (e.g., optocoupler LED, error amp references). Exceeding 20 mA causes reference droop and oscillator frequency shift; for >20 mA loads, an external buffer or LDO is required.
UC2844BN 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:
- -25°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-Mini DIP
UC2844BN FAQ
1.How can I place an order for UC2844BN through Aetrix?
Please submit a Request for Quotation (RFQ) for UC2844BN 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 UC2844BN reliable?
The price and inventory of UC2844BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC2844BN is usually 5 days.
3.What payment methods are accepted for UC2844BN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC2844BN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC2844BN?
UC2844BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC2844BN 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 UC2844BN?
For technical support, including UC2844BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC2844BN requirements.
6.How does Aetrix verify that UC2844BN is sourced from the original manufacturer or authorized distributors?
All UC2844BN 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 UC2844BN meets industry standards.
7.What is the process for return or replacement of UC2844BN?
All UC2844BN units undergo pre-shipment inspection (PSI). If there is an issue with UC2844BN, 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 UC2844BN part is unused and in its original packaging.
Return procedure for UC2844BN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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