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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Power Supply Controllers, Monitors

Texas Instruments UC2843AD8G4

Name: UC2843AD8G4
Brand: Texas Instruments
SKU: UC2843AD8G4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: UC2843AD8G4

Manufacturer:: Texas Instruments

Category:: Power Supply Controllers, Monitors

Package:: 8-SOIC (0.154", 3.90mm Width)

Datasheet:: UC2843AD8G4.pdf

Description:: IC REG CTRLR MULT TOPOLOGY 8SOIC

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Product details

Overview

UC2843AD8G4 from Texas Instruments is a current-mode PWM controller in an 8-pin SOIC (D) package, designed for off-line and DC-DC converters. It delivers up to 1 A gate drive output, operates up to 500 kHz, features 8.3 mA trimmed oscillator discharge current, and provides pulse-by-pulse current limiting with 1 V internal ISENSE clamp - used in universal-input flyback SMPS.

For engineers reviewing the UC2843AD8G4 datasheet, UC2843AD8G4 pinout, UC2843AD8G4 application, or UC2843AD8G4 equivalent, key selection criteria include UVLO thresholds (8.4 V turn-on / 7.6 V turn-off), 5 V ±1% internal reference, 0.5 mA max start-up current, and compatibility with WEBENCH® Power Designer for custom flyback design.

Technical Context

The UC2843AD8G4 implements peak-current-mode control using an internal error amplifier (80 dB open-loop gain, 1 MHz unity-gain bandwidth) and a dedicated current-sense comparator with 150–300 ns propagation delay. Its oscillator uses RT/CT programming with trimmed 8.3 mA discharge current, enabling precise duty-cycle control up to 100% and stable operation across temperature.

During undervoltage lockout (UVLO), the device draws only 0.3–0.5 mA and forces OUTPUT low while sinking ≥10 mA at ≤1.2 V - preventing parasitic MOSFET turn-on via Miller effect. The totem-pole output drives external FET gates directly, supporting both isolated and non-isolated topologies including flyback, forward, and boost.

Key Specifications

Parameter	Value and Actual Design Meaning
Operating frequency	Up to 500 kHz - enables compact magnetics and high-efficiency power conversion in space-constrained designs.
Start-up current	< 0.5 mA - reduces power loss in high-voltage start-up resistors for off-line applications.
Oscillator discharge current	8.3 mA (typ) - ensures accurate, temperature-stable maximum duty cycle programming without external trimming.
UVLO threshold	8.4 V (turn-on) / 7.6 V (turn-off) - narrow hysteresis optimized for regulated DC-DC input operation.
Output drive capability	±1 A - directly drives medium-power MOSFETs without external buffer stages.
Reference voltage	5.0 V ±1% (4.95–5.05 V) - stable, internally trimmed bandgap reference for precision feedback loop control.
ISENSE clamp	1 V (max) - limits peak current sense signal to protect internal comparator and ensure consistent current limiting.

Pinout & Package

UC2843AD8G4 is housed in an 8-pin SOIC (D) package measuring 4.90 mm × 6.00 mm, with standard JEDEC MS-012AC footprint and gull-wing leads.

Pin/Terminal	Circuit Role	Design Meaning
1 - COMP	Error amplifier output	Low-impedance node (80 dB gain, 1 MHz GBW) feeding PWM comparator; sinks up to 6 mA for loop compensation.
2 - FB	Error amplifier inverting input	Accepts voltage feedback signal (e.g., optocoupler emitter); sets output regulation point via 2.5 V internal reference.
3 - ISENSE	Current sense input	Direct connection to current-sense resistor; clamped at 1 V to define cycle-by-cycle peak current limit.
4 - RT/CT	Oscillator timing input	Connects external RT (5–100 kΩ) and CT (470 pF–4.7 nF) to set switching frequency and max duty cycle.
5 - GND	Signal ground reference	Common return for analog circuitry; must be star-connected to minimize noise coupling into FB/COMP/ISENSE.
6 - OUTPUT	Gate driver output	Totem-pole stage sourcing/sinking up to 1 A; requires series gate resistor to limit dV/dt and EMI.
7 - VCC	Bias supply input	Accepts 11–30 V DC; powers internal circuitry and gate driver; UVLO active below 7.6 V.
8 - VREF	5 V reference output	Stable 5 V source (≤10 mA load); bypassed with 1 µF ceramic capacitor; used for RT/CT bias and external circuitry.

Key Features

Feature	Design Value
Automatic feedforward compensation	Compensates for input voltage variations in real time, improving line transient response without additional components.
Pulse-by-pulse current limiting	Enables robust overcurrent protection per switching cycle, allowing safe operation under short-circuit or overload conditions.
Enhanced load response characteristics	Combines fast error amplifier (1 MHz GBW) and low-latency current sensing (≤300 ns) for rapid output regulation during load steps.
Double pulse suppression	Prevents false triggering of the PWM latch during noise spikes or startup transients, ensuring clean single-pulse output per cycle.
Internally-trimmed bandgap reference	Delivers 5.0 V ±1% over –40°C to +85°C, eliminating need for external reference ICs in most feedback networks.

Applications

Industrial Switch-Mode PSU	Universal-Input Flyback Adapter
Use Scenario: Regulated 24 V/5 A output from 3-phase 400 V AC industrial mains using active PFC front-end followed by UC2843AD8G4-controlled flyback. IC Role / Device Role / Timing Role: Primary-side PWM controller implementing peak-current-mode regulation with 100% duty cycle capability and UVLO hysteresis matched to auxiliary winding bias stability. Use Value: Enables compact, cost-effective industrial PSU design with <0.5 mA start-up current reducing heat in high-voltage start-up network and 8.3 mA trimmed oscillator discharge ensuring repeatable max duty cycle across production lots.	Use Scenario: 12 V/4.33 A wall adapter accepting 85–265 V AC input, using UC2843AD8G4 in discontinuous conduction mode (DCM) flyback with TL431 + optocoupler feedback. IC Role / Device Role / Timing Role: Core current-mode controller managing primary-side switching, current sensing, and error amplification; RT/CT pins configure 65 kHz operation for EMI compliance and transformer optimization. Use Value: Delivers tight output regulation (±2%) and fast load-step response (<100 µs recovery) due to integrated 1-MHz error amplifier and 1 V ISENSE clamp, while 0.5 mA start-up current minimizes dissipation in 1 MΩ start-up resistor.
DC-DC Buck-Boost Converter	Telecom Battery Backup Module
Use Scenario: 48 V input to 12 V/3 A output buck-boost converter for railway signaling equipment, operating in wide ambient (–40°C to +85°C). IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller providing cycle-by-cycle current limiting and automatic feedforward compensation to maintain regulation during 48 V input ripple. Use Value: 8.4 V/7.6 V UVLO thresholds prevent erratic operation during brownout events; 5 V reference accuracy (±1%) ensures stable feedback across temperature, reducing need for calibration.	Use Scenario: 24 V battery-backed DC-DC module supplying 5 V/2 A to critical control logic during AC mains failure in telecom base station cabinets. IC Role / Device Role / Timing Role: Primary-side PWM controller in isolated forward converter topology, using UC2843AD8G4's high-current output to drive synchronous rectifier gate drivers via bootstrap circuit. Use Value: ±1 A output drive supports direct gate driving of dual N-channel MOSFETs; 500 kHz max frequency allows use of small planar magnetics, reducing board area by >30% vs 100 kHz alternatives.

Industrial Switch-Mode PSU

Universal-Input Flyback Adapter

Use Scenario: Regulated 24 V/5 A output from 3-phase 400 V AC industrial mains using active PFC front-end followed by UC2843AD8G4-controlled flyback.

IC Role / Device Role / Timing Role: Primary-side PWM controller implementing peak-current-mode regulation with 100% duty cycle capability and UVLO hysteresis matched to auxiliary winding bias stability.

Use Value: Enables compact, cost-effective industrial PSU design with <0.5 mA start-up current reducing heat in high-voltage start-up network and 8.3 mA trimmed oscillator discharge ensuring repeatable max duty cycle across production lots.

Use Scenario: 12 V/4.33 A wall adapter accepting 85–265 V AC input, using UC2843AD8G4 in discontinuous conduction mode (DCM) flyback with TL431 + optocoupler feedback.

IC Role / Device Role / Timing Role: Core current-mode controller managing primary-side switching, current sensing, and error amplification; RT/CT pins configure 65 kHz operation for EMI compliance and transformer optimization.

Use Value: Delivers tight output regulation (±2%) and fast load-step response (<100 µs recovery) due to integrated 1-MHz error amplifier and 1 V ISENSE clamp, while 0.5 mA start-up current minimizes dissipation in 1 MΩ start-up resistor.

DC-DC Buck-Boost Converter

Telecom Battery Backup Module

Use Scenario: 48 V input to 12 V/3 A output buck-boost converter for railway signaling equipment, operating in wide ambient (–40°C to +85°C).

IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller providing cycle-by-cycle current limiting and automatic feedforward compensation to maintain regulation during 48 V input ripple.

Use Value: 8.4 V/7.6 V UVLO thresholds prevent erratic operation during brownout events; 5 V reference accuracy (±1%) ensures stable feedback across temperature, reducing need for calibration.

Use Scenario: 24 V battery-backed DC-DC module supplying 5 V/2 A to critical control logic during AC mains failure in telecom base station cabinets.

IC Role / Device Role / Timing Role: Primary-side PWM controller in isolated forward converter topology, using UC2843AD8G4's high-current output to drive synchronous rectifier gate drivers via bootstrap circuit.

Use Value: ±1 A output drive supports direct gate driving of dual N-channel MOSFETs; 500 kHz max frequency allows use of small planar magnetics, reducing board area by >30% vs 100 kHz alternatives.

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
UC3843BD1R2G	Same pinout, but rated for 0°C to 70°C ambient (vs UC2843AD8G4's –40°C to +85°C); UVLO thresholds identical (8.4 V/7.6 V).	Suitable for commercial-grade consumer adapters; not qualified for industrial or extended-temperature environments.	Select UC3843BD1R2G only when ambient temperature remains within 0–70°C and industrial qualification is unnecessary.
TL494CN	Fixed-frequency voltage-mode controller (not current-mode); dual-output, 50% max duty cycle per channel; no integrated 1 V ISENSE clamp or 8.3 mA oscillator trim.	Requires external current sensing and slope compensation for >50% duty cycles; better suited for push-pull or half-bridge topologies.	Choose TL494CN only when dual-output capability or voltage-mode control is required; not drop-in compatible for UC2843AD8G4 current-mode designs.

Compared with UC3843BD1R2G and TL494CN, UC2843AD8G4 offers extended temperature range, current-mode architecture with built-in cycle-by-cycle limiting, and factory-trimmed oscillator discharge - making it uniquely suitable for ruggedized, high-reliability flyback and DC-DC converters where thermal stability and fault tolerance are critical.

Availability

UC2843AD8G4 is available at Aetrix Electronics and suitable for industrial switch-mode PSUs, universal-input flyback adapters, and telecom battery backup modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for UC2843AD8G4 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies, with decades of expertise in power conversion ICs.

The UCx84xA product line was engineered specifically for cost-sensitive, high-volume current-mode SMPS designs - emphasizing low start-up current, precise oscillator control, and robust gate drive in industry-standard packages.

FAQ

What is the maximum operating frequency of the UC2843AD8G4?

The UC2843AD8G4 supports oscillator frequencies up to 500 kHz, as confirmed in the Electrical Characteristics table (Section 5.5) and Functional Description (Section 6.1). This maximum is achievable with appropriate RT/CT component selection - TI recommends RT between 5 kΩ and 100 kΩ and CT between 470 pF and 4.7 nF. Operation beyond 500 kHz is not guaranteed and may degrade timing accuracy or stability. The UC2843AD8G4 maintains full functionality including pulse-by-pulse current limiting and UVLO protection across its entire specified frequency range.

Does the UC2843AD8G4 require an external current-sense resistor?

Yes, the UC2843AD8G4 requires an external current-sense resistor connected to the ISENSE pin (Pin 3). This resistor converts inductor or switch current into a voltage signal that the internal comparator monitors. The UC2843AD8G4 clamps the ISENSE input at 1 V maximum, so the resistor value is selected to produce ≤1 V at the desired peak current (e.g., 0.1 Ω for 10 A peak). No internal sense element exists - all current sensing is external and programmable. The device does not integrate a shunt or MOSFET R_DS(on) measurement circuit.

What is the purpose of the VREF pin on the UC2843AD8G4?

Pin 8 (VREF) on the UC2843AD8G4 provides a precision 5.0 V ±1% output derived from an internally trimmed bandgap reference. It supplies bias current to the RT/CT timing network and can power external circuitry such as optocoupler LEDs or error amplifier references - but must be loaded with ≤10 mA. A 1 µF high-frequency ceramic capacitor is mandatory for stability. Unlike some controllers, VREF is not used for internal oscillator biasing alone; it serves as a system-level reference node, and its short-circuit protection (≈100 mA) prevents damage during accidental overloads.

How does the UC2843AD8G4 handle undervoltage lockout (UVLO)?

The UC2843AD8G4 implements UVLO with a turn-on threshold of 8.4 V and turn-off threshold of 7.6 V, providing 0.8 V hysteresis. During UVLO, the device draws only 0.3–0.5 mA and forces OUTPUT low while sinking ≥10 mA at ≤1.2 V - actively pulling down external gate nodes to prevent parasitic turn-on. This behavior is documented in Section 6.3.4 and Table 5.5. Once VCC exceeds 8.4 V, the 5 V reference ramps up and normal operation begins. UVLO ensures reliable startup and shutdown sequencing in DC-DC converters with regulated inputs.

Can the UC2843AD8G4 be used in a voltage-mode control configuration?

Yes, the UC2843AD8G4 can operate in voltage-mode control, though it is optimized for peak-current-mode operation. In voltage mode, the error amplifier output (COMP) directly controls PWM duty cycle without current-sense feedback - requiring external slope compensation for stability above 50% duty cycle. Section 6.4.1 confirms dual-mode capability, and Figure 6-7 illustrates slope compensation implementation. However, pulse-by-pulse current limiting, automatic feedforward, and enhanced load response are only fully realized in current-mode configuration. Voltage-mode use sacrifices key UC2843AD8G4 advantages and demands careful loop compensation design.

UC2843AD8G4 Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: -

Package/Case:: 8-SOIC (0.154", 3.90mm Width)

Packaging:: Tube

Product Status:: Discontinued at Digi-Key

Programmable:: -

Applications:: PWM Controller

Voltage - Input:: -0.3V ~ 6.3V

Voltage - Supply:: 7.6V ~ 30V

Current - Supply:: 11 mA

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: Automotive

Qualification:: AEC-Q100

Mounting Type:: Surface Mount

Supplier Device Package:: 8-SOIC

UC2843AD8G4 FAQ

1.How can I place an order for UC2843AD8G4 through Aetrix?

Please submit a Request for Quotation (RFQ) for UC2843AD8G4 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 UC2843AD8G4 reliable?

The price and inventory of UC2843AD8G4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC2843AD8G4 is usually 5 days.

3.What payment methods are accepted for UC2843AD8G4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC2843AD8G4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for UC2843AD8G4?

UC2843AD8G4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your UC2843AD8G4 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 UC2843AD8G4?

For technical support, including UC2843AD8G4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC2843AD8G4 requirements.

6.How does Aetrix verify that UC2843AD8G4 is sourced from the original manufacturer or authorized distributors?

All UC2843AD8G4 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 UC2843AD8G4 meets industry standards.

7.What is the process for return or replacement of UC2843AD8G4?

All UC2843AD8G4 units undergo pre-shipment inspection (PSI). If there is an issue with UC2843AD8G4, 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 UC2843AD8G4 part is unused and in its original packaging.

Return procedure for UC2843AD8G4:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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