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STMicroelectronics UC2843BN
- Part No.:
- UC2843BN
- Manufacturer:
- STMicroelectronics
- Category:
- DC DC Switching Controllers
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
UC2843BN.pdf
- Description:
- IC REG CTRLR BST/FLYBK 8-MINIDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,932
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Product details
Overview
UC2843BN 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 (250 kHz guaranteed), latching PWM for cycle-by-cycle current limiting, 8.5 V/7.9 V UVLO thresholds, 5 V reference output, and 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 UC2843BN datasheet, UC2843BN pinout, UC2843BN application, or UC2843BN equivalent, key selection criteria include its 8-pin DIP package, 96% max duty cycle, low 0.5 mA start-up current, and compatibility with current-sense-based overcurrent protection in isolated AC-DC adapters and industrial SMPS designs.
Technical Context
The UC2843BN implements current-mode control via a high-speed current-sense comparator (150–300 ns delay) that terminates switch conduction when sensed inductor current reaches the error amplifier's output voltage threshold. Its internal oscillator uses RT/CT programming with discharge current trimming (7.5–8.8 mA) to guarantee frequency stability across temperature and supply voltage.
UVLO logic provides hysteresis (8.5 V turn-on / 7.9 V turn-off), ensuring clean startup and brownout recovery. The error amplifier (65–90 dB open-loop gain, 0.7–1 MHz bandwidth) supports Type II/III compensation networks, while the totem-pole output stage delivers fast rise/fall times (50–150 ns into 1 nF) and rail-to-rail swing under load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 250 kHz guaranteed at 25°C; programmable up to 500 kHz via RT/CT network. |
| UVLO Thresholds | 8.5 V (on) / 7.9 V (off); enables reliable startup in low-input-voltage DC-DC applications. |
| Max Duty Cycle | 96% typical; supports high step-down ratio topologies without external duty-cycle clamping. |
| Reference Voltage | 5.00 V ±50 mV; internally trimmed and stable over line/load/temperature for precision feedback. |
| Output Drive | ±1 A peak sink/source; directly drives gate capacitance of medium-power MOSFETs (e.g., <500 pF). |
| Start-up Current | <0.5 mA at 6.5 V; reduces auxiliary winding losses in offline flyback designs. |
| Error Amp GBW | 0.7–1 MHz; sufficient for stable loop compensation in 100–300 kHz switching converters. |
Pinout & Package
UC2843BN is housed in an 8-pin plastic dual in-line package (Minidip), with 0.3-inch body width and 2.54 mm lead pitch. Pin 5 serves as the common ground for both analog and power sections, requiring single-point grounding for noise immunity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (COMP) | Error amplifier output | Provides access to EA output for external Type II/III compensation network connection. |
| 2 (VFB) | Inverting input of error amplifier | Connects to resistor divider from output; sets regulation point via 2.5 V internal reference. |
| 3 (ISENSE) | Current sense input | Accepts voltage proportional to primary current; triggers PWM latch at ~1 V threshold. |
| 4 (RT/CT) | Oscillator timing node | RC network here programs frequency and max duty cycle; CT discharges at 7.5–8.8 mA. |
| 5 (GROUND) | Analog + power ground | Single-point return for all internal circuits; critical for noise-free current sensing. |
| 6 (OUTPUT) | Totem-pole gate driver | Sources/sinks ±1 A; drives N-MOSFET gates directly; low-state during UVLO. |
| 7 (Vi / VCC) | Supply input | Operates from 8.5–30 V; self-limiting above 30 V; powers internal bias and reference. |
| 8 (VREF) | 5 V reference output | Supplies charging current to CT via RT; stable ±50 mV; short-circuit protected. |
Key Features
| Feature | Design Value |
|---|---|
| Latching PWM control | Ensures single-pulse-per-cycle operation, preventing subharmonic oscillation in continuous conduction mode. |
| Internally trimmed 5 V reference | Eliminates need for external reference IC; maintains ±1% accuracy over temperature and load. |
| Automatic feed-forward compensation | Uses input voltage variation to modulate oscillator ramp slope, improving line transient response. |
| Low-startup-current UVLO | Enables use with high-impedance startup resistors, reducing standby power in no-load conditions. |
| High-current totem-pole output | Drives MOSFET gates without external buffer, reducing BOM count and layout complexity. |
Applications
| AC-DC Adapter | Flyback SMPS |
|---|---|
Use Scenario: 5–24 V, 10–65 W universal-input AC-DC adapter for consumer electronics. IC Role / Device Role / Timing Role: Primary-side PWM controller implementing current-mode regulation and cycle-by-cycle overcurrent protection. Use Value: 8.5 V UVLO allows reliable startup from low-voltage auxiliary windings; 96% duty cycle supports wide input range without external clamp. | Use Scenario: Isolated 12 V/2 A flyback converter in industrial IoT power modules. IC Role / Device Role / Timing Role: Fixed-frequency (250 kHz) current-mode controller with optocoupler feedback and primary-side sensing. Use Value: 500 kHz capability enables smaller magnetics; ±1 A output drives 400 V/2 A MOSFETs directly, reducing gate drive loss. |
| DC-DC Boost Converter | Offline Forward Converter |
Use Scenario: 12 V to 48 V boost converter for telecom intermediate bus generation. IC Role / Device Role / Timing Role: Current-mode PWM controller regulating output voltage using inductor current feedback. Use Value: Fast 150 ns current-sense path enables precise peak-current limiting; 0.5 mA start-up current minimizes auxiliary supply burden. | Use Scenario: 36–75 V input, 5 V/10 A forward converter in telecom rectifier systems. IC Role / Device Role / Timing Role: Primary-side controller managing synchronous rectification timing and reset winding control. Use Value: Trimmed oscillator ensures tight frequency tolerance across temperature; 5 V reference powers auxiliary circuitry and sensing ICs. |
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 |
|---|---|---|---|
| UC3843BN | Same pinout and electrical specs; rated for 0°C to 70°C ambient vs. UC2843BN's –40°C to 150°C junction range. | Preferred for commercial-grade equipment where extended temperature operation is not required. | Select UC3843BN for cost-sensitive commercial designs; UC2843BN for industrial/automotive environments. |
| TL494CN | Dual-output, fixed-frequency PWM with adjustable dead time; lacks integrated current-sense comparator and 5 V reference. | Requires external current sensing and reference; suited for push-pull or half-bridge topologies. | Choose TL494CN only when dual-output or adjustable dead-time control is mandatory; not drop-in compatible. |
Compared with UC3843BN, UC2843BN offers wider operating temperature range and identical functionality; TL494CN requires additional components for current-mode operation and cannot replace UC2843BN without topology redesign.
Availability
UC2843BN is available at Aetrix Electronics and suitable for AC-DC adapters, flyback SMPS, and industrial DC-DC converters requiring stable component supply, long-lifecycle support, and consistent parametric performance across temperature extremes.
Supply support for UC2843BN 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.
The UCx84xB series was developed specifically for cost-effective, high-reliability current-mode switching power supplies-targeting off-line and DC-DC applications where minimal external components and robust fault protection are essential.
FAQ
What is the maximum recommended switching frequency for UC2843BN?
The UC2843BN oscillator is guaranteed at 250 kHz but supports operation up to 500 kHz using appropriate RT/CT values. At higher frequencies, ensure PCB layout minimizes parasitic inductance on ISENSE and GROUND paths to maintain current-sense accuracy and avoid false triggering.
How does the UC2843BN implement cycle-by-cycle current limiting?
It compares the voltage at pin 3 (ISENSE) against the error amplifier's output (via COMP pin). When ISENSE exceeds ~1 V, the PWM latch resets immediately, terminating the current pulse. This occurs within 150–300 ns, enabling precise per-cycle peak-current control without external comparators.
Can UC2843BN drive a P-channel MOSFET directly?
No-its OUTPUT pin is a totem-pole stage that sources current when high and sinks when low, optimized for driving N-channel MOSFET gates. Driving a P-channel device would require level-shifting or an external driver; design guidance recommends N-MOSFETs for primary-side switching.
What is the purpose of the VREF pin (pin 8) beyond providing 5 V?
Pin 8 supplies regulated 5 V and also provides the charging current for the CT capacitor through the external RT resistor. This integrated timing current source eliminates the need for a separate bias supply and ensures oscillator frequency accuracy independent of VCC variations.
UC2843BN 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):
- 7.6V ~ 30V
- Frequency - Switching:
- Up to 500kHz
- Duty Cycle (Max):
- 96%
- 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
UC2843BN FAQ
1.How can I place an order for UC2843BN through Aetrix?
Please submit a Request for Quotation (RFQ) for UC2843BN 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 UC2843BN reliable?
The price and inventory of UC2843BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC2843BN is usually 5 days.
3.What payment methods are accepted for UC2843BN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC2843BN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC2843BN?
UC2843BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC2843BN 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 UC2843BN?
For technical support, including UC2843BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC2843BN requirements.
6.How does Aetrix verify that UC2843BN is sourced from the original manufacturer or authorized distributors?
All UC2843BN 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 UC2843BN meets industry standards.
7.What is the process for return or replacement of UC2843BN?
All UC2843BN units undergo pre-shipment inspection (PSI). If there is an issue with UC2843BN, 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 UC2843BN part is unused and in its original packaging.
Return procedure for UC2843BN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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