Product details

Topology Flyback, Boost, Duty cycle (Max) (%) 100 Supply voltage (Max) (V) 30 UVLO thresholds on/off (V) 16/10 Features Adjustable Switching Frequency, Error Amplifier, Multi-topology Operating temperature range (C) -40 to 85 Rating Catalog Frequency (Max) (kHz) 500 Gate drive (Typ) (A) 1
Topology Flyback, Boost, Duty cycle (Max) (%) 100 Supply voltage (Max) (V) 30 UVLO thresholds on/off (V) 16/10 Features Adjustable Switching Frequency, Error Amplifier, Multi-topology Operating temperature range (C) -40 to 85 Rating Catalog Frequency (Max) (kHz) 500 Gate drive (Typ) (A) 1
PDIP (P) 8 93 mm² 9.81 x 9.43 SOIC (D) 14 52 mm² 8.65 x 6 SOIC (D) 8 19 mm² 3.91 x 4.9
  • Low Start-Up Current (<0.5 mA)
  • Trimmed Oscillator Discharge Current
  • Current Mode Operation to 500 kHz
  • Automatic Feed-Forward Compensation
  • Latching PWM for Cycle-by-Cycle Current Limiting
  • Internally Trimmed Reference With Undervoltage Lockout
  • High-Current Totem-Pole Output Undervoltage Lockout With Hysteresis
  • Double-Pulse Suppression

  • Low Start-Up Current (<0.5 mA)
  • Trimmed Oscillator Discharge Current
  • Current Mode Operation to 500 kHz
  • Automatic Feed-Forward Compensation
  • Latching PWM for Cycle-by-Cycle Current Limiting
  • Internally Trimmed Reference With Undervoltage Lockout
  • High-Current Totem-Pole Output Undervoltage Lockout With Hysteresis
  • Double-Pulse Suppression

The TL284xB and TL384xB series of control integrated circuits provide the features that are necessary to implement off-line or dc-to-dc fixed-frequency current-mode control schemes, with a minimum number of external components. Internally implemented circuits include an undervoltage lockout (UVLO) and a precision reference that is trimmed for accuracy at the error amplifier input. Other internal circuits include logic to ensure latched operation, a pulse-width modulation (PWM) comparator that also provides current-limit control, and a totem-pole output stage designed to source or sink high-peak current. The output stage, suitable for driving N-channel MOSFETs, is low when it is in the off state.

The TL284xB and TL384xB series are pin compatible with the standard TL284x and TL384x with the following improvements. The start-up current is specified to be 0.5 mA (max), while the oscillator discharge current is trimmed to 8.3 mA (typ). In addition, during undervoltage lockout conditions, the output has a maximum saturation voltage of 1.2 V while sinking 10 mA (VCC = 5 V).

Major differences between members of these series are the UVLO thresholds and maximum duty-cycle ranges. Typical UVLO thresholds of 16 V (on) and 10 V (off) on the TLx842B and TLx844B devices make them ideally suited to off-line applications. The corresponding typical thresholds for the TLx843B and TLx845B devices are 8.4 V (on) and 7.6 V (off). The TLx842B and TLx843B devices can operate to duty cycles approaching 100%. A duty-cycle range of 0% to 50% is obtained by the TLx844B and TLx845B by the addition of an internal toggle flip-flop, which blanks the output off every other clock cycle.The TL284xB-series devices are characterized for operation from -40°C to 85°C. The TL384xB-series devices are characterized for operation from 0°C to 70°C.

The TL284xB and TL384xB series of control integrated circuits provide the features that are necessary to implement off-line or dc-to-dc fixed-frequency current-mode control schemes, with a minimum number of external components. Internally implemented circuits include an undervoltage lockout (UVLO) and a precision reference that is trimmed for accuracy at the error amplifier input. Other internal circuits include logic to ensure latched operation, a pulse-width modulation (PWM) comparator that also provides current-limit control, and a totem-pole output stage designed to source or sink high-peak current. The output stage, suitable for driving N-channel MOSFETs, is low when it is in the off state.

The TL284xB and TL384xB series are pin compatible with the standard TL284x and TL384x with the following improvements. The start-up current is specified to be 0.5 mA (max), while the oscillator discharge current is trimmed to 8.3 mA (typ). In addition, during undervoltage lockout conditions, the output has a maximum saturation voltage of 1.2 V while sinking 10 mA (VCC = 5 V).

Major differences between members of these series are the UVLO thresholds and maximum duty-cycle ranges. Typical UVLO thresholds of 16 V (on) and 10 V (off) on the TLx842B and TLx844B devices make them ideally suited to off-line applications. The corresponding typical thresholds for the TLx843B and TLx845B devices are 8.4 V (on) and 7.6 V (off). The TLx842B and TLx843B devices can operate to duty cycles approaching 100%. A duty-cycle range of 0% to 50% is obtained by the TLx844B and TLx845B by the addition of an internal toggle flip-flop, which blanks the output off every other clock cycle.The TL284xB-series devices are characterized for operation from -40°C to 85°C. The TL384xB-series devices are characterized for operation from 0°C to 70°C.

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Technical documentation

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Type Title Date
* Data sheet High Performance Current-Mode PWM Controllers datasheet (Rev. B) 02 Jul 2007
Application note Flyback Selection Guide PDF | HTML 23 Jun 2022
Application note Conditioning a Switch-mode Power Supply Current Signal Using TI Op Amps (Rev. A) PDF | HTML 11 Jun 2021
Application note Understanding Inverting Buck-Boost Power Stages in Switch Mode Power Supplies (Rev. B) 12 Mar 2019
Application note UCC38C42 Family of High-Speed BiCMOS Current-Mode PWM Controllers 07 Feb 2002
Application note DN-26 UC3842A Low-Cost Start-up and Fault Protection Circuit 05 Sep 1999
Application note DN-27 UC1842/UC1842A Family - Summary of Functional Differences 05 Sep 1999
Application note DN-29 UC3842A Family - Frequency Foldback Technique Provides Protection 05 Sep 1999
Application note DN-30 Programmable Electronic Circuit Breaker 05 Sep 1999
Application note DN-40 The Effects of Oscillator Discharge Current Variations on Maximum Duty 05 Sep 1999
Application note DN-42A Design Considerations for Transitioning from UC3842 to the New UCC3802 05 Sep 1999
Application note DN-62 Switching Power Supply Topology Voltage Mode vs. Current Mode 05 Sep 1999
Application note DN-65 Considerations in Powering BiCMOS ICs 05 Sep 1999
Application note DN-89 Comparing the UC3842, UCC3802, and UCC3809 Primary Side PWM Controllers 05 Sep 1999
Application note U-100A UC3842/3/4/5 Provides Low-Cost Current-Mode Control 05 Sep 1999
Application note U-111, Practical Considerations in Current Mode Power Supplies 05 Sep 1999
Application note Understanding Boost Power Stages In Switchmode Power Supplies 04 Mar 1999
Application note Understanding Buck Power Stages In Switchmode Power Supplies 04 Mar 1999

Design & development

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Reference designs

PMP22899 — 24-W, 120-VAC to 24-VDC buck converter reference design

This reference design uses a TL2842B as a high-side buck to convert a 120-Vac input to a 24-Vdc output capable of 1-A loading. At full load, it acheives a low peak-to-peak output ripple and over 88% efficiency at full load. This reference design was built using a 2-layer PCB and single-sided (...)
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PDIP (P) 8 View options
SOIC (D) 14 View options
SOIC (D) 8 View options

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