Current-Mode PWM Controller - TL3843

TL3843 (ACTIVE)

Current-Mode PWM Controller

Description

The TL284x and TL384x 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. Some of the internally implemented circuits are an undervoltage lockout (UVLO), featuring a start-up current of less than 1 mA, and a precision reference 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.

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 TLx842 and TLx844 devices make them ideally suited to off-line applications. The corresponding typical thresholds for the TLx843 and TLx845 devices are 8.4 V (on) and 7.6 V (off). The TLx842 and TLx843 devices can operate to duty cycles approaching 100%. A duty-cycle range of 0 to 50% is obtained by the TLx844 and TLx845 by the addition of an internal toggle flip-flop, which blanks the output off every other clock cycle.

The TL284x-series devices are characterized for operation from –40°C to 85°C. The TL384x devices are characterized for operation from 0° to 70°C.

Features

  • Optimized for Off-Line and dc-to-dc Converters
  • Low Start-Up Current (<1 mA)
  • Automatic Feed-Forward Compensation
  • Pulse-by-Pulse Current Limiting
  • Enhanced Load-Response Characteristics
  • Undervoltage Lockout With Hysteresis
  • Double-Pulse Suppression
  • High-Current Totem-Pole Output
  • Internally Trimmed Bandgap Reference
  • 500-kHz Operation
  • Error Amplifier With Low Output Resistance
  • Designed to Be Interchangeable With UC2842 and UC3842 Series

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Topology
Control Method
Duty Cycle (Max) (%)
Frequency (Max) (kHz)
UVLO Thresholds On/Off (V)
Regulated Outputs (#)
Special Features
Rating
Operating Temperature Range (C)
Pin/Package
Approx. Price (US$)
TL3843 TL3842 TL3844 TL3845
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Current     Current     Current     Current    
100     100     50     50    
500     500     500     500    
8.4/7.6     16/10     16/10     8.4/7.6    
1     1     1     1    
Adjustable Switching Frequency
Error Amplifier    
Adjustable Switching Frequency
Error Amplifier    
Adjustable Switching Frequency
Error Amplifier    
Adjustable Switching Frequency
Error Amplifier    
Catalog     Catalog     Catalog     Catalog    
0 to 70     0 to 70     0 to 70     0 to 70    
14SOIC
8PDIP
8SOIC    
14SOIC
8SOIC
8PDIP    
14SOIC
8PDIP
8SOIC    
14SOIC
8PDIP
8SOIC    
0.40 | 1ku     0.40 | 1ku     0.43 | 1ku     0.43 | 1ku    

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