UC3845J
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Unitrode UC3845J

Manufacturer No:
UC3845J
Manufacturer:
Unitrode
Package:
Bulk
Description:
UC3845 CURRENT MODE PWM CONTROLL
Delivery:
Payment:
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iso45001
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Product Introduction

Overview

The UC3845J is a current-mode PWM (Pulse Width Modulation) controller integrated circuit produced by Unitrode, now part of Texas Instruments. This component is specifically designed for off-line and DC-to-DC converter applications, requiring minimal external components. It features a trimmed oscillator for precise duty cycle control, a temperature-compensated reference, a high-gain error amplifier, and a current sensing comparator. The UC3845J is widely used in power supply systems due to its robust and efficient design.

Key Specifications

Parameter Symbol Value Unit
Supply Voltage VCC 30 V
Output Current IO ±1 A
Analog Inputs (Pin 2, 3) V(ANA) -0.3 to 6.3 V
Error Amp Output Sink Current ISINK (E.A) 10 mA
Power Dissipation at TA≤25°C (8DIP) PD 1200 mW
Storage Temperature Range TSTG -65 ~ +150 °C
Oscillation Frequency f 47 to 57 kHz
Maximum Duty Cycle D(Max) 47 to 50% %
Start-Up Current IST 0.45 to 1 mA
Operating Supply Current ICC(OPR) 14 to 17 mA

Key Features

  • Trimmed oscillator for precise duty cycle control
  • Temperature-compensated reference
  • High-gain error amplifier
  • Current sensing comparator
  • High current totem-pole output for driving a Power MOSFET
  • Low start-up current
  • Maximum duty cycle clamp
  • Under-voltage lockout (UVLO) with hysteresis
  • Operating frequency up to 500 kHz

Applications

The UC3845J is primarily used in off-line and DC-to-DC converter applications. It is suitable for a variety of power supply systems, including:

  • Switch-mode power supplies
  • DC-to-DC converters
  • High-frequency power supplies
  • Power factor correction circuits

Q & A

  1. What is the primary function of the UC3845J?

    The UC3845J is a current-mode PWM controller designed for off-line and DC-to-DC converter applications.

  2. What is the maximum supply voltage for the UC3845J?

    The maximum supply voltage is 30V.

  3. What is the typical operating frequency range of the UC3845J?

    The typical operating frequency range is 47 to 57 kHz.

  4. Does the UC3845J have under-voltage lockout (UVLO) protection?
  5. What is the maximum duty cycle for the UC3845J?

    The maximum duty cycle is 47 to 50%.

  6. What type of output does the UC3845J have?

    The UC3845J has a high current totem-pole output for driving a Power MOSFET.

  7. What are the typical start-up and operating supply currents for the UC3845J?

    The start-up current is 0.45 to 1 mA, and the operating supply current is 14 to 17 mA.

  8. What is the storage temperature range for the UC3845J?

    The storage temperature range is -65°C to +150°C.

  9. Can the UC3845J operate at 100% duty cycle?

    No, the UC3845J can operate with a maximum duty cycle of 50%.

  10. What are some common applications of the UC3845J?

    Common applications include switch-mode power supplies, DC-to-DC converters, high-frequency power supplies, and power factor correction circuits.

Product Attributes

Output Type:Transistor Driver
Function:Step-Up, Step-Down, Step-Up/Step-Down
Output Configuration:Positive
Topology:- 
Number of Outputs:1
Output Phases:1
Voltage - Supply (Vcc/Vdd):12V ~ 28V
Frequency - Switching:100kHz
Duty Cycle (Max):48%
Synchronous Rectifier:No
Clock Sync:No
Serial Interfaces:- 
Control Features:Frequency Control
Operating Temperature:0°C ~ 70°C (TA)
Mounting Type:Through Hole
Package / Case:8-CDIP (0.300", 7.62mm)
Supplier Device Package:8-CDIP
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Similar Products

Part Number UC3845J UC3846J UC3845N UC3843J UC3844J UC3845D
Manufacturer Unitrode Texas Instruments Texas Instruments Unitrode Texas Instruments Fairchild Semiconductor
Product Status Active Active Active Active Active Obsolete
Output Type Transistor Driver Transistor Driver Transistor Driver Transistor Driver Transistor Driver Transistor Driver
Function Step-Up, Step-Down, Step-Up/Step-Down Step-Up, Step-Up/Step-Down Step-Up, Step-Down, Step-Up/Step-Down Step-Up, Step-Down, Step-Up/Step-Down Step-Up, Step-Down, Step-Up/Step-Down Step-Up, Step-Down, Step-Up/Step-Down
Output Configuration Positive Positive Positive, Isolation Capable Positive, Isolation Capable Positive, Isolation Capable Positive or Negative, Isolation Capable
Topology - Boost, Flyback, Forward Converter, Half-Bridge, Push-Pull Boost, Buck, Buck-Boost, Flyback, Forward Boost, Buck, Buck-Boost, Flyback, Forward Boost, Buck, Buck-Boost, Flyback, Forward Boost, Buck, Buck-Boost, Flyback, Forward
Number of Outputs 1 2 1 1 1 1
Output Phases 1 1 1 1 1 1
Voltage - Supply (Vcc/Vdd) 12V ~ 28V 6.95V ~ 40V 12V ~ 28V 12V ~ 28V 12V ~ 28V 7.6V ~ 30V
Frequency - Switching 100kHz 500kHz Up to 500kHz Up to 500kHz Up to 500kHz Up to 500kHz
Duty Cycle (Max) 48% 50% 48% 97% 48% 48%
Synchronous Rectifier No Yes No No No No
Clock Sync No Yes No No No No
Serial Interfaces - - - - - -
Control Features Frequency Control Current Limit, Enable, Frequency Control, Soft Start Frequency Control Frequency Control Frequency Control Frequency Control
Operating Temperature 0°C ~ 70°C (TA) 0°C ~ 70°C (TA) 0°C ~ 70°C (TA) 0°C ~ 70°C (TA) 0°C ~ 70°C (TA) 0°C ~ 70°C (TA)
Mounting Type Through Hole Through Hole Through Hole Through Hole Through Hole Surface Mount
Package / Case 8-CDIP (0.300", 7.62mm) 16-CDIP (0.300", 7.62mm) 8-DIP (0.300", 7.62mm) 8-CDIP (0.300", 7.62mm) 8-CDIP (0.300", 7.62mm) 14-SOIC (0.154", 3.90mm Width)
Supplier Device Package 8-CDIP 16-CDIP 8-PDIP 8-CDIP 8-CDIP 14-SOIC

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