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UC3843BNG

Current-mode PWM controller, 500kHz, 5V ref, UVLO 8.4V/7.6V, 8-PDIP

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Manufacturer Part：

UC3843BNG

Package：

8-PDIP (9.81 x 6.35 x 4.57mm)

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Description

Product Overview

The UC3843BNG from Texas Instruments is a current-mode PWM controller for off-line and DC-DC converters. It features 500kHz switching, trimmed oscillator for precise frequency, current-sense comparator, totem-pole output, and undervoltage lockout (8.4V/7.6V) in an 8-pin PDIP package.

Key Specifications

Manufacturer Texas Instruments
Type Current-Mode PWM Controller
Switching Frequency Up to 500kHz
Reference Voltage 5.0V +-1%
UVLO Threshold 8.4V on / 7.6V off
Max Duty Cycle 100%
Output Current +-1A peak totem-pole
Supply Voltage Up to 30V
Start-Up Current 0.5mA max
Operating Current 11mA typical
Package 8-PDIP
Operating Temperature 0C to +70C

Features

  • Current-mode PWM operation up to 500kHz
  • Trimmed oscillator for precise frequency control
  • 5V reference with +-1% accuracy
  • Undervoltage lockout with hysteresis (8.4V/7.6V)
  • Totem-pole output for direct MOSFET drive
  • Current-sense comparator with 1V threshold
  • Automatic feedforward compensation
  • Pulse-by-pulse current limiting
  • Low start-up current: 0.5mA

Applications

  • Off-line flyback and forward converters
  • DC-DC buck, boost, and buck-boost converters
  • Battery charger power supplies
  • Industrial power supply designs

The Texas Instruments UC3843BNG is a high-performance fixed-frequency current-mode PWM controller optimized for off-line and DC-DC converter applications. The UC3843B is the industry-standard controller for flyback and forward converter topologies. It features a trimmed oscillator for precise frequency, a temperature-compensated 5V reference with +-1% accuracy, a high-gain error amplifier, current-sense comparator, and a totem-pole output stage capable of +-1A peak current for direct MOSFET drive. The current-mode architecture provides inherent input voltage feedforward, excellent line regulation, and simplified loop compensation compared to voltage-mode control. Pulse-by-pulse current limiting ensures safe operation during overload and short-circuit conditions.

The UC3843BNG operates as a fixed-frequency current-mode PWM controller: 1) Oscillator: An external resistor (RT) and capacitor (CT) set the switching frequency up to 500kHz. The oscillator generates a clock pulse that sets the output flip-flop at the beginning of each switching cycle. 2) Current-Mode Control: The output switch is turned on at the start of each cycle. When the voltage across the current-sense resistor (sensed at the ISENSE pin) reaches the threshold set by the error amplifier output, the comparator resets the flip-flop, turning off the switch. This creates natural input voltage feedforward and simplifies loop compensation to a single-pole response. 3) Error Amplifier: Compares the output voltage feedback with the 5V reference, adjusting the current-sense threshold to maintain regulation. 4) UVLO: The 8.4V start/7.6V stop threshold prevents operation at insufficient supply voltage, ensuring clean start-up.

Pin Name Type Function
1 COMP I/O Error amplifier output / compensation
2 VFB Input Error amplifier inverting input (feedback)
3 ISENSE Input Current sense input (1V threshold)
4 RT/CT I/O Oscillator timing RC network
5 GND Ground Ground
6 OUTPUT Output PWM output (totem-pole, +-1A)
7 VCC Power Supply voltage (up to 30V)
8 VREF Output 5V reference output (+-1%)
  • Off-line flyback converter for consumer electronics power adapters
  • DC-DC boost converter for battery-powered industrial equipment
  • Isolated telecom power supply with current-mode control
Manufacturer Part Number Package Notes
TI UC3842BNG 8-PDIP 16V/10V UVLO version
TI UC3844BNG 8-PDIP 50% max duty cycle version
onsemi UC3843BVD1G 8-SOIC SMD version, same function
ST UC3843BN 8-PDIP Second source, equivalent
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Certification
We have obtained a number of professional certifications and built our own professional testing laboratory.This ensures that every product we deliver to our customers meets the highest quality requirements.We conduct tests in strict accordance with procedures to ensure stable product quality and accurate parameters.To guarantee genuine original parts, we also cooperate with reliable third-party testing institutions for strict quality inspection.We always attach great importance to quality and fully comply with industry standards, relevant regulations, and ISO 9001:2015 requirements.

Shipping & Payment

All electronic components we source from our partnered supply chains go through strict incoming inspections.Through careful testing, we ensure everything delivered to customers is genuine original parts and meets quality requirements.In addition, we keep complete inspection records to make the entire supply chain process clear and traceable.

Certification
We have obtained a number of professional certifications and built our own professional testing laboratory.This ensures that every product we deliver to our customers meets the highest quality requirements.We conduct tests in strict accordance with procedures to ensure stable product quality and accurate parameters.To guarantee genuine original parts, we also cooperate with reliable third-party testing institutions for strict quality inspection.We always attach great importance to quality and fully comply with industry standards, relevant regulations, and ISO 9001:2015 requirements.

Service & Packaging

All electronic components we source from our partnered supply chains go through strict incoming inspections.Through careful testing, we ensure everything delivered to customers is genuine original parts and meets quality requirements.In addition, we keep complete inspection records to make the entire supply chain process clear and traceable.

Certification
We have obtained a number of professional certifications and built our own professional testing laboratory.This ensures that every product we deliver to our customers meets the highest quality requirements.We conduct tests in strict accordance with procedures to ensure stable product quality and accurate parameters.To guarantee genuine original parts, we also cooperate with reliable third-party testing institutions for strict quality inspection.We always attach great importance to quality and fully comply with industry standards, relevant regulations, and ISO 9001:2015 requirements.

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